Basic Anatomy - Tissues & Organs There are many different types of cells in the human body. None of these cells function well on there own, they are part of the larger organism that is called - you.
Tissues Cells group together in the body to form tissues - a collection of similar cells that group together to perform a specialized function. There are 4 primary tissue types in the human body: epithelial tissue, connective tissue, muscle tissue and nerve tissue.
Epithelial Tissue - The cells of epithelial tissue pack tightly together and form continuous sheets that serve as linings in different parts of the body. Epithelial tissue serve as membranes lining organs and helping to keep the body's organs separate, in place and protected. Some examples of epithelial tissue are the outer layer of the skin, the inside of the mouth and stomach, and the tissue surrounding the body's organs.
Connective Tissue - There are many types of connective tissue in the body. Generally speaking, connective tissue adds support and structure to the body. Most types of connective tissue contain fibrous strands of the protein collagen that add strength to connective tissue. Some examples of connective tissue include the inner layers of skin, tendons, ligaments, cartilage, bone and fat tissue. In addition to these more recognizable forms of connective tissue, blood is also considered a form of connective tissue.
Muscle Tissue - Muscle tissue is a specialized tissue that can contract. Muscle tissue contains the specialized proteins actin and myosin that slide past one another and allow movement. Examples of muscle tissue are contained in the muscles throughout your body.
Nerve Tissue - Nerve tissue contains two types of cells: neurons and glial cells. Nerve tissue has the ability to generate and conduct electrical signals in the body. These electrical messages are managed by nerve tissue in the brain and transmitted down the spinal cord to the body. Organs Organs are the next level of organization in the body. An organ is a structure that contains at least two different types of tissue functioning together for a common purpose. There are many different organs in the body: the liver, kidneys, heart, even your skin is an organ. In fact, the skin is the largest organ in the human body and provides us with an excellent example for explanation purposes. The skin is composed of three layers: the epidermis, dermis and subcutaneous layer. The epidermis is the outermost layer of skin. It consists of epithelial tissue in which the cells are tightly packed together providing a barrier between the inside of the body and the outside world. Below the epidermis lies a layer of connective tissue called the dermis. In addition to providing support for the skin, the dermis has many other purposes. The dermis contains blood vessels that nourish skin cells. It contains nerve tissue that provides feeling in the skin. And it contains muscle tissue that is responsible for giving you 'goosebumps' when you get cold or frightened. The subcutaneous layer is beneath the dermis and consists mainly of a type of connective tissue called adipose tissue. Adipose tissue is more commonly known as fat and it helps cushion the skin and provide protection from cold temperatures.
A cross-section of skin
Epidermis
Dermis
Subcutaneous layer
Organ Systems Organ systems are composed of two or more different organs that work together to provide a common function. There are 10 major organ systems in the human body, they are the:
Skeletal System:
Image courtesy of A. McGann
Major Role: The main role of the skeletal system is to provide support for the body, to protect delicate internal organs and to provide attachment sites for the organs.
Major Organs: Bones, cartilage, tendons and ligaments.
Muscular System:
Image courtesy of G. Huang
Major Role: The main role of the muscular system is to provide movement. Muscles work in pairs to move limbs and provide the organism with mobility. Muscles also control the movement of materials through some organs, such as the stomach and intestine, and the heart and circulatory system.
Major Organs: Skeletal muscles and smooth muscles throughout the body.
Circulatory System:
Image courtesy of G. Huang
Major Role: The main role of the circulatory system is to transport nutrients, gases (such as oxygen and CO2), hormones and wastes through the body.
Major Organs: Heart, blood vessels and blood.
Nervous System:
Image courtesy of G. Huang
Major Role: The main role of the nervous system is to relay electrical signals through the body. The nervous system directs behaviour and movement and, along with the endocrine system, controls physiological processes such as digestion, circulation, etc.
Major Organs: Brain, spinal cord and peripheral nerves.
Respiratory System:
Image courtesy of A. McGann
Major Role: The main role of the respiratory system is to provide gas exchange between the blood and the environment. Primarily, oxygen is absorbed from the atmosphere into the body and carbon dioxide is expelled from the body.
Major Organs: Nose, trachea and lungs.
Digestive System:
Image courtesy of A. McGann
Major Role: The main role of the digestive system is to breakdown and absorb nutrients that are necessary for growth and maintenance.
Major Organs: Mouth, esophagus, stomach, small and large intestines.
Excretory System:
Image courtesy of G. Huang
Major Role: The main role of the excretory system is to filter out cellular wastes, toxins and excess water or nutrients from the circulatory system.
Major Organs: Kidneys, ureters, bladder and urethra.
Endocrine System:
Image courtesy of G. Huang
Major Role: The main role of the endocrine system is to relay chemical messages through the body. In conjunction with the nervous system, these chemical messages help control physiological processes such as nutrient absorption, growth, etc.
Major Organs: Many glands exist in the body that secrete endocrine hormones. Among these are the hypothalamus, pituitary, thyroid, pancreas and adrenal glands.
Reproductive System:
Female:
Male: Images courtesy of G. Huang
Major Role: The main role of the reproductive system is to manufacture cells that allow reproduction. In the male, sperm are created to inseminate egg cells produced in the female.
Major Organs: Female (top): ovaries, oviducts, uterus, vagina and mammary glands. Male (bottom): testes, seminal vesicles and penis.
Lymphatic/Immune System:
Image not available
Major Role: The main role of the immune system is to destroy and remove invading microbes and viruses from the body. The lymphatic system also removes fat and excess fluids from the blood.
Major Organs: Lymph, lymph nodes and vessels, white blood cells, T- and B- cells. For more information on human anatomy, try these other sites:
The National Library of Medicine has an excellent page that includes links to Medline, a searchable medical research database, and the Visible Human Project's animations, which include anatomical illustrations from human cadavers and an animated trip through the Visible Human male cryosections (770k movie linked here).
The Informative Graphics Corp. has put together a wonderful Human Anatomy On-line program.
The University of Washington's Digital Anatomist Interactive Atlas has some interesting computer generated illustrations of the brain, the heart and a knee cross-section.
Andrew McGann's Look Inside the Human Body has more information on some organ systems.
The Upper Freehold Regional School District's AP Biology class has put together a nice summary of the Human Organ Systems.
The Indianapolis-Marion County Public Library's Inside the Human Body site has organ system info.
Saturday, February 6, 2010
Sunday, December 27, 2009
The Right Combination, Unmatched Evidence and Decreased Resistance – Cook Spectrum catheters are impregnated with minocycline and rifampin to give your patients the best protection possible against catheter-related bloodstream infection (CRBSI).
Central Venous Catheters (CVCs)
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Product Ordering
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Central Venous Catheters (CVCs)
Cook Medical has a complete line of Spectrum central venous catheters to seamlessly replace your existing CVCs, including your power-injectable CVCs. To support your process bundle, Spectrum catheters are packaged with the industry's widest range of comprehensive tray components.
View Our Comprehensive Product Offering
Product Ordering
Con
Friday, August 14, 2009
General Principles: Chemotherapy
General Principles of Chemotherapy
Many of the same basic principles apply to antimicrobial, antiparasitic and anticancer chemotherapy.
Selective Toxicity:
Selective toxicity refers to the ability of the drug to targets sites that are relative specific to the microorganism responsible for infection.
Sometimes these sites are unique to the microorganism or simply more essential to survival of the microorganism than to the host.
Examples of such specific or relatively specific sites include specific fungal or bacterial cell wall synthesizing enzymes, the bacterial ribosomal or the molecular machinery of viral replication.
Chambers, H.F., Hadley, W. K. and Jawetz, E. Introduction to Antimicrobial Agents in Basic and Clinical Pharmacology, (Katzung, B. G., ed) Appleton-Lange, 1998, p. 723.
Chemotherapeutic Drug Targets
Targets for Antimicrobial/Antiviral Drugs
Bacterial Cell Wall Synthesis Inhibitors
Agents that Increase Cell Membrane Permeability
Protein Synthesis Inhibitors: interfere with 30S or 50S bacterial ribosome function
Drugs that Bind to the 30S bacterial ribosomal subunit, leading to cell death
Agents that interfere with nucleic acid synthesis
Antimetabolites
Inhibitors of Viral Replication
Bacterial cell wall synthesis inhibitors:
penicillins
cephalosporins
cycloserine
vancomycin (Vancocin)
bacitracin
miconazole (Monistat)(imidazole antifungal)
ketoconazole (Nizoral)(imidazole antifungal)
clotrimazole (Mycelex)(imidazole antifungal)
Agents that increase cell membrane permeability
polymixins (detergent)
colistimethate (detergent)
nystatin (Mycostatin)(polyene antifungal)
amphotericin B (Fungizone, Amphotec)(polyene antifungal)
Protein synthesis inhibitors: interfere with 30S or 50S bacterial ribosome function.
Bacteriostatic
chloramphenicol (Chloromycetin)
tetracyclines
erythromycin estolate (Ilosone)
clindamycin (Cleocin)
Drugs that bind to the 30S bacterial ribosomal subunit, leading to cell death.
Bacteriocidal
Aminoglycosides (e.g.gentamicin (Garamycin), tobramycin (Nebcin))
Agents that interfere with nucleic acid synthesis
rifamycins (rifampin (Rimactane)): inhibits DNA-dependent RNA polymerase
quinolones: inhibit gyrase
Antimetabolites
sulfonamides
trimethoprim (generic)
Some Nucleic Acid Analogs (Antivirals): inhibitors of viral replication
zidovudine (Retrovir, AZT, azidothymidine)
ganciclovir (DHPG, Cytovene)
vidarabine (Vira-A)
acyclovir (Zovirax)
Chambers, H.F and Sande, M.A. Antimicrobial Agents in,In, Goodman and Gillman's The Pharmacologial Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) TheMcGraw-Hill Companies, Inc.,1996, pp.1029-1030
Disease caused by bacteria and the the role of the host response in outcome of chemotherapeutic intervention.
Importance of Host Response
Host response as manifest in the inflammatory response is crucial for both the interruption resolution of the infection and for the basis of the infection's signs and symptoms.
The ability of effective antibiotic chemotherapy depends not only on appropriate selection of medication(s), dosage, and interval, but also on the host immune response.
Pier, G.B. Molecular Mechanism of Bacterial Pathogenesis., In Harrison's Principles of Internal Medicine (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1994, p. 592.
Disease Manifestations of Bacterial Disease
Disease manifestation of bacterial infection involves:
Colonization
Invasion: Bacterial invasion refers to the presence of bacteria in tissue sites normally sterile.
Examples:
Gram-negative rods in the blood stream result in septisemia and bacteremia without requiring endotoxin involvement
Pneumococcal pneumonia is due the growth of Streptococcus pneumoniae in the lung while bacterial endotoxins do not appear to play a role.
Disease that occurs after bactermia and invasion of the meninges by meningitis-producing bacteria (N. meningitidis, H. influenzae, E. coli, K1 and group B streptococci) is due to tissue destruction secondary to bacterial growth and host inflammation.
Toxin production and release
Toxin Elaboration
Clinicial manifestation of some bacterial infections are primarily due to toxin elaboration.
For example: Botulinum toxin: C. botulinum, Tetanus toxins: C. tetani, Diptheria toxin causes the disease due to infection with C. diphtheriae
Some specific aspects of bacterial disease are caused by elaborated toxins
Enterotoxins cause the diarrhea associated with E. coli, Salmonella, Shigella, Staphylococcus and V. cholerae.
Toxins involved in Toxic shock syndrome caused by Staphylococci, steptococci, P. aeruginosa and Bordatella: include: Toxic shock syndrome toxin (TSST), erythrogenic toxin, exotoxin A and pertussis toxin.
Staphylococcal enterotoxins, TSST-1 and streptococcal exotoxins have been classified as superantigens which are capable of inducing certain T cell proliferation without processing of the protein toxin by antigen-presenting cells.
This process involves, in part, the elaboration of IL-1 and TNF-alpha which may cause many clinical features seen in staphylococcal toxic shock syndrome, scarlet fever, streptococcal toxic shock syndrome.
Pier, G.B. Molecular Mechanism of Bacterial Pathogenesis., In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 855.
Endotoxins (lipid A portion of gram-negative LPS) may cause many clinical presentations seen in gram-negative bacterial sepsis: Toxins involve include: IL-1 and TNF-alpha--
Clinical presentations include:fever, intravascular coagulation, shock, and muscle proteolysis.
Pier, G.B. Molecular Mechanism of Bacterial Pathogenesis., In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 855.
Importance of Host Response
Host response as manifest in the inflammatory response is crucial for both interruption and infection resolution and the infection's signs and symptoms.
The ability of effective antibiotic chemotherapy depends not only on appropriate selection of medication(s), dosage, and interval, but also on the host immune response.
Pier, G.B. Molecular Mechanism of Bacterial Pathogenesis., In Harrison's Principles of Internal Medicine (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1994, p. 592.
Pharmacokinetic barriers that reduce the effectiveness of treatment
Introduction
Pharmacokinetic components include absorption, distribution, biotransformation (metabolism) and excretion.
Pharmacokinetic "profile" of antibacterial describes the drug concentration in tissues and serum as a function of time after administration.
The profile depends on the agent's absorption, distribution, biotransformation and excretion.
In therapeutics "trough" concentration (low) and "peak" concentrations (high) are important.
Pharmcokinetic information is used to establish dose and dosing intervals.
Absorption
Oral Therapy predominates for the following principal reasons: lower costs and fewer adverse effects
Another consideration, however, is that the oral route of administration is associated with a substantial range of bioavailabililty. For example, oral availability is only about 10% to 20% erythromycin estolate (Ilosone) and penicillin G, whereas bioavailability is about 100% for clindamycin (Cleocin), doxycycline (Vibramycin, Doryx) methonidazole, and trimethoprim (generic) sulfamethoxazole (Gantanol).
Bioavailability differences are NOT clinically important if the concentration of drug at the site of infection is sufficient to inhibit (bacteriostatic) or to kill (bacteriocidal).
Factors that can influence oral bioavailability include the presence of food in the digestive tract and drug interactions for example quinolones with metal cations.
Intramuscular
Administration by this route offers 100% bioavailable, but not widely used because of injection site pain can be usually ease of intravenous administration in the hospital inpatient setting.
Intravenous Administration:
Intravenous administration, however, would be appropriate if for example, oral agents proved ineffective, if there is a special concern about bioavailability, if larger doses are required relative to those typically obtained from oral dosing or because the bioavailability will be known to be 100%.
Distribution:
Antibacterial concentrations must exceed that required to inhibit bacterial growth (MIC).
Given that most infections are located outside the blood stream, the drug must distribute to those sites.
Drug concentration at most sites are similar to serum levels.
Some sites are "protected", however. these protected sites include the eye, prostate, and cardiac sites where there may be vegetative growth (e.g. around valves in a bacterial endocarditis setting)
High parentral doses may be required in these circumstances.
Poor efficacy may be related to adequate concentrations, but local unfavorable conditions.
For example, the activity of aminoglycosides is reduced in acidic pH, common at sites of infection. Biological constituants present in absesses may also inhibit the activity of antibacterials, thus requiring surgical dranage prior to efficacious therapy.
Archer,G.L. and Polk, R.E. Treatment and Prophylaxis of Bacterial Infections, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 860.
Mechanisms for chemotherapeutic drugs resistance
Bacterial resistance may occur because the drug does not reach its target site, drug is inactivated, or there is some sort of molecular alteration in the target itself, possibly due to mutation.
Resistance may occur because enzymes at or near the cell surface inactivate the antibiotic; the cell membrane is impermeable to the drug; there is an absence of aqueous channels (porins) through which the drug will reach the cell interior; there is a lack of a necessary transport system to support drug translocation; the transport mechanism is present but inoperative due to anaerobic metabolism; there are target site changes that results in reduced or absent antibacterial drug efficacy.
How Bacteria Acquire Resistance
Resistance may be acquired by vertical transfer, i.e. acquired by mutation and then passed to daughter cells
Mutations: Specific genetic mutations are the molecular basis for resistance to streptomycin (ribosomal mutation), to quinolones (DNA gyrase gene mutation) and to rifampin (Rimactane) (RNA polymerase gene mutation)
The mutation to rifampin (Rimactane) is an example of a single-step mutation: In this case E. coli or Staph. aureus exposure to rifampin results in highly resistant strain due to a point mutation in the RNA polymerase gene such that the polymerase protein no longer binds rifampin.
More usually, acquired by horizontal transfer of resistance factors from a donor cell, perhaps of a different species by transformation which involves the incorporation of DNA found free environment into the bacterial genome.
An example of this process is the basis of penicillin resistance in. pneumococci and Neisseria gonorrhoeae.
Penicillin-resistant pneumococci produce different PBPs (penicillin-binding proteins). These different PBPs exhibit relatively low affinity for penicillin compared to wild type pneumococci.
These different PBPs arise from integration of foreign DNA which were most likely from a closely related streptococcal strain into the PBP gene by a process of homologous recombination.
Transduction-based resistance occurs when a bacteriophage which includes bacterial DNA in its protein coat infects the bacteria. This bacterial DNA may contain a gene confiring resistance to antibacterial drugs.
Examples of this process:
Staphylococcus aureus strain resistance development to penicillin may occur by transduction (Some bacteriophages carry plasmids [extrachromosomal self-replicating DNA] that code for penicillinase
Other phages can transfer genes which confer resistance to tetracycline (Achromycin), erythromycin estolate (Ilosone), and chloramphenicol (Chloromycetin).
Conjugation is another important mechanism for single and multi-drug resistance development. In conjugation direct passage of resistance-confering DNA between bacteria proceeds by way of a bridge
The genetic material transfer in conjugation requires two elements: an R-determinant plasmid which codes for the resistance and a resistance-transfer factor (RTF) plasmid which contains the genes necessary for the bacterial conjugation process. Occasionally two plasmids join to form a complete R factor
Some genes that are responsible for resistance are located on transposons which can move from location to location within plasmid and bacterial genomes.
Conjugation mediated resistance is particularly important in gram-negative bacilli.
Enterococci may contain plasmids that spread resistance among gram-positive organisms
Vancomycin (Vancocin) resistance in enterococcal strains appears to occur as a result of the conjugation mechanism.
Conjugation is not a high efficiency mechanism for resistance development. Unfortunately, antibiotic use provides selection pressures which facilitate the elaboration of resistance bacteria. Furthermore, enteric bacteria carrying plasmids for multidrug resistance is now a worldwide, serious concern.
Resistance acquired by horizontal transfer can disseminate rapidly through the bacterial population by clonal spread as well as by continuing genetic material exchange between cells of the same or different susceptible strains.
Chambers, H.F and Sande, M.A. Antimicrobial Agents in,In, Goodman and Gillman's The Pharmacologial Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) TheMcGraw-Hill Companies, Inc.,1996, pp.1031.
Microbial Resistance and Specific Drugs
Resistance: ß-Lactams
Most common among several mechanisms by which bacteria develop resistance to ß-Lactam antibiotics is by elaboration of the enzyme ß-lactamase, which hydrolyzes the ß-lactam ring.
Beta-lactamase genes may be found in both gram-positive and gram-negative bacteria. Resistance may be reduced by agents which bind to some beta-lactamases. Examples of these drugs include clavulanic acid and sulbactam.
Another mechanism by which bacteria may develop resistance to beta-lactam antibiotics is by changes in penicillin-binding proteins (PBPs). These changes may occur either by mutation of existing PBP genes or more often by the acquisition of new PBP genes. For the latter case, unimportant example is staphylococcal resistance to methicillin (Staphcillin).
In addition to mutation of existing PBP genes, bacterial also acquiring new "pieces or segments" of PBP genes. This process appears important in resistance development for certain pneumococcal, gonococcal, and meningococcal strains)
Yet another mechanism is observed in gram-negative bacteria and follows from alteration of genes that code for certain outer membrane proteins (porins). The expression of altered porins reduce membrane permeability to penicillins. This process appears important in cephalosporin-resistance of Enterbacteriaceae and that of Pseudomonas species to ureidopenicillins.
Multiple resistance mechanisms can exist within the same bacterial cell.
Archer,G.L. and Polk, R.E. Treatment and Prophylaxis of Bacterial Infections, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 859.
Chloramphenicol (Chloromycetin) resistance:
This resistance occurs because of the formation of an acetylated chloramphenicol (Chloromycetin) derivative which is not biologically active.
A plasmid-encoded enzyme, chloramphenicol acetyltransferase catalyzes the acetyl group transfer which would otherwise not occur
Vancomycin (Vancocin) resistance is an important problem in antibiotic chemotherapy. For example, vancomycin (Vancocin)-resistant enterococci strains are worldwide.
The resistance mechanism involves transfer between cells and is plasmid mediated.
The specific alteration is a change in the peptidoglycan stem peptide which causes a loss of the vancomycin (Vancocin) binding target.
Often significant vancomycin (Vancocin) resistance is observed with enterococci strains all the same time most staphylococci aureus and staphylococci epidermis remain vancomycin (Vancocin) sensitive.
Resistance to tetracyclines:
The most common mechanism for gram-negative bacterial resistance follows from insertion of a plasmid-encoded active-efflux pump which translocates tetracycline (Achromycin) out of the cell.
For gram-positive bacteria, resistance may follow from the above mechanism (active efflux) or is a result of changes in the tetracycline ribosomal target site.
Aminoglycoside resistance:
The most common resistance mechanism is antibiotic inactivation by enzyme-mediated covalent bond modification. Modifications occur as a result of acetyl, adenyl or phosphate group transfer.
Enzymes which catalyze these group transfers and confer antibody resistance are plasmid localized.
As a consequence of these molecular modifications, the modified antibiotic becomes less active secondary to reduced transport and attenuated ribosomal target site binding.
Aminoglycoside-modifying enzymes occur in both gram-negative and gram-positive bacteria.
Mupirocin resistance: Resistance to this topical drug is due to alteration in the target site which is an isoleucine tRNA synthetase enzyme. Following modification, the enzyme no longer binds mupirocin (Bactriban)
Macrolides and Licosamides resistance. Antibiotic from these categories target gram-positive bacteria.
Resistance to these antibiotics result from plasmid-mediated ribosomal RNA methylation that interferes with antibiotic binding.
Specific antibiotic susceptible to this type of resistance include erythromycin, newer macrolides and clindamycin (Cleocin).
Quinolone-resistance:
Quinone resistance including resistance to newer fluoroquinolones has developed quickly in Staphylococcus and Pseudomonas strains.
The resistance mechanism involves a mutation in the drug target site, which is DNA gyrases. The mediated DNA gyrases are not susceptible to inhibition by quinolones.
Other resistance mechanisms involve in gram-negative strains, mutations in porins that cause the bacterial membrane to lose its permeability to the drug.in gram-positive organisms, resistance follows the development of the capability that enables the cell to actively pump out the drug from the cell.
Rifampin (Rimactane) resistance can rapidly develop as a result of target site mutations. The target in this case is RNA polymerase. Following mutation of the polymerase, rifampin (Rimactane) no longer binds.
Rapid strain resistance development has become a major limiting factor in rifampin (Rimactane) use in management of susceptible staphylococci thus requiring rifampin (Rimactane) to be combined with another antistaphylococcal drug.
Multiple Antibiotic Resistance Summary
It is increasingly common for one bacterium to be resistant to several antibacterial drugs.
Mechanisms:
Acquisition of multiple, unrelated resistance genes (several steps required)
Mutation in a single gene which results in resistance to unrelated drugs. (single step)
Bacteria resistant due to acquisition of new genes:
hospital-associated gram-negative bacteria
enterococci
staphylococci
community-acquired salmonellae strains
gonococci
pneumococci.
Single gene mutations: usually affecting porins of gram-negative bacteria involve:
ß-lactams
quinolones
tetracycline
chloramphenicol (Chloromycetin)
trimethoprim (generic)
Strains resistant to all known antibacterial drugs have been identified.
Archer,G.L. and Polk, R.E. Treatment and Prophylaxis of Bacterial Infections, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 859.
Clinical indications and rationale for the use of multiple drugs at the same time (combination chemotherapy)
Single Agent Chemotherapy
Single most specific drug is preferable if the infecting bacteria has been identified.
Administration of a single drug with a narrow spectrum of action is desirable because (a) alteration of normal flora is minimized (which in turn reduces the likelihood of overgrowth of resistant nosocomial bacteria (e.g. Candida albicans, enterococci, Clostridium difficile), (b) reduces toxicity which may be associated with multiple drug regimens and (c) reduces cost.
Archer,G.L. and Polk, R.E. Treatment and Prophylaxis of Bacterial Infections, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 862.
Combination Chemotherapy
Combination chemotherapy may be warrented to:
Decrease the likelihood of emergence of resistant mutants. A single agent will be effective against sensitive organisms, but not against those that have developed a mutated "target" site, which is no longer susceptible or has diminished susceptibility to the drug. In this case the single drug will select out the mutant, resistant strain. This effect is more likely when the concentration of the antibacterial agent approximates the MIC (minimum inhibitory concentration).
Examples:
rifampin (Rimactane) : staphylococci
ciprofloxacin (Cipro): staphylococci and Pseudomonas.
imipenem: Pseudomonas
aminoglycosides: staphylococci
A second agent, which acts by a different mechanism, may prevent the emergence of the resistant strain (e.g. impenem + aminoglycoside for systemic Pseudomonas).
To take advantage of additive/synergistic action against some bacteria. Synergistic or additive activity occurs if the MIC or MBC of each agent is lowered in the presence of the other. Accordingly, each drug is more efficacious when combined with the other. (1) Certain ß-lactam-aminoglycoside combinations are effective against enterococci, viridans streptococci, and P. aeruginosa. (2) Combination of trimethoprim-sulfamethoxazole (Bactrim) is effective against many enteric gram negative bacteria. (3) Most other combinations are not clinically surperior compared to administration of the more efficacious single drug component.
Some combinations are less effective than a single agent: penicillin plus tetracycline (Achromycin) against pneumonococci.
To provide therapy when multiple pathogens may be or are known to be present . If a mixture of pathogens is thought to be present and/or the patient is critically ill, combination therapy may be warrented. [Multiple Pathogens may be present in intra-abdominal or brain abscesses and limb infection in diabetic patients; in critical illness fevers in neutropenic patients, acute aspiration pneumonia (oral flora) by hospitalized patients, septic shock or sepsis syndrome. However, monotherapy should be started if a single infecting bacterium that can be appropriately treated with a single drug has been identified
Archer,G.L. and Polk, R.E. Treatment and Prophylaxis of Bacterial Infections, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 862.
Rationale for chemoprophylaxis
Chemoprophylaxis
A manifestation of antibiotic misuse is that 30% to 50% of the time, the antibiotic is prescribed to prevent rather treat an infection.
Prophylaxis is more likely to be effective if a single, effective, nontoxic drug is used to prevent infection by a specific organism or to eliminate a recently established infection.
Examples of effective chemoprophylaxis:
Penicillin G prevents infection by group-A streptococci.
Intermittent use of trimethoprim (generic) sulfamethoxazole (Gantanol) prevents recurrent urinary tract infections
Prevention of endocarditis in patients with valvular heart lesions who are to undergo a surgical procedure.
The most extensive use of chemoprophylaxis is prevention of wound infections following surgery.
Chambers, H.F and Sande, M.A. Antimicrobial Agents in,In, Goodman and Gillman's The Pharmacologial Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) TheMcGraw-Hill Companies, Inc.,1996, pp.1049-1050
Appropriate and Inappropriate Uses of Chemotherapy
Appropriate Use
Before the organism is identified: either combination therapy or a single broad spectrum agent may be used.
After the organism is identified, a low-toxicity regimen with a narrow-spectrum drug is indicated.
Selection of the drug should be goverened by its selectivity for the most likely involved bacteria and its toxicity.
First decide if an antibiotic is indicated since antibiotics may be toxic. Inappropriate use may hinder diagnosis, and can result in development of resistant bacterial strains
Some Clinical Issues
Optimal empirical treatment requires knowledge of the antibiotic sensitivity of the organisms which is most likely causing the infection.
Assessment with Gram's stain and other tests must be used to narrow the list of pathogens.
In life threatening situations, the selection of a single narrow-spectrum agent may not be possible and broad coverage would be indicated until a definitive identification is possible.
Chambers, H.F and Sande, M.A. Antimicrobial Agents in,In, Goodman and Gillman's The Pharmacologial Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) TheMcGraw-Hill Companies, Inc.,1996, pp.1054-1055
Inappropriate Uses
Treatment of Untreatable Infections:
The infection is viral.
Antimicrobial treatment of measles, mumps and 90% of upper respiratory infections are inappropriate.
Treatment of fever of unknown origin:
Antimicrobials are not antipyretic agents.
Pyrexia of short duration, without localizaing signs, is most likely due to viral infection.
Three infections may be associated with prolonged fever:
tuberculosis
hidden intra-abdominal abscesses
infective endocarditis.
other causes: cancer metabolic disorders hepatitis atypical rheumatoid arthritis
Improper dosage:
Some drugs, such as the aminoglycosides, are frequently administered at subtherapeutic dosages because of concern about toxicity.
Clinical treatment failure and selection of resistant strains may result.
Inappropriate Dependence on Chemotherapy Alone:
Some disorders require both chemotherapy and a surgical procedure, especially if significant amount of necrotic tissue is present.
Example : Pneumonia in a patient with empyema (accumulation of pus) may be effectively manage following drainage
Lack of Adquate Bacteriological Information:
About one-half of antimicrobial therapy is given to hospitalized patients without support from microbiological data. [clinical judgment alone];
Antimicrobial therapy must be individualized, not administered based on prescribing habit alone.
Chambers, H.F and Sande, M.A. Antimicrobial Agents in,In, Goodman and Gillman's The Pharmacological Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) TheMcGraw-Hill Companies, Inc.,1996, pp.1054-1055
Many of the same basic principles apply to antimicrobial, antiparasitic and anticancer chemotherapy.
Selective Toxicity:
Selective toxicity refers to the ability of the drug to targets sites that are relative specific to the microorganism responsible for infection.
Sometimes these sites are unique to the microorganism or simply more essential to survival of the microorganism than to the host.
Examples of such specific or relatively specific sites include specific fungal or bacterial cell wall synthesizing enzymes, the bacterial ribosomal or the molecular machinery of viral replication.
Chambers, H.F., Hadley, W. K. and Jawetz, E. Introduction to Antimicrobial Agents in Basic and Clinical Pharmacology, (Katzung, B. G., ed) Appleton-Lange, 1998, p. 723.
Chemotherapeutic Drug Targets
Targets for Antimicrobial/Antiviral Drugs
Bacterial Cell Wall Synthesis Inhibitors
Agents that Increase Cell Membrane Permeability
Protein Synthesis Inhibitors: interfere with 30S or 50S bacterial ribosome function
Drugs that Bind to the 30S bacterial ribosomal subunit, leading to cell death
Agents that interfere with nucleic acid synthesis
Antimetabolites
Inhibitors of Viral Replication
Bacterial cell wall synthesis inhibitors:
penicillins
cephalosporins
cycloserine
vancomycin (Vancocin)
bacitracin
miconazole (Monistat)(imidazole antifungal)
ketoconazole (Nizoral)(imidazole antifungal)
clotrimazole (Mycelex)(imidazole antifungal)
Agents that increase cell membrane permeability
polymixins (detergent)
colistimethate (detergent)
nystatin (Mycostatin)(polyene antifungal)
amphotericin B (Fungizone, Amphotec)(polyene antifungal)
Protein synthesis inhibitors: interfere with 30S or 50S bacterial ribosome function.
Bacteriostatic
chloramphenicol (Chloromycetin)
tetracyclines
erythromycin estolate (Ilosone)
clindamycin (Cleocin)
Drugs that bind to the 30S bacterial ribosomal subunit, leading to cell death.
Bacteriocidal
Aminoglycosides (e.g.gentamicin (Garamycin), tobramycin (Nebcin))
Agents that interfere with nucleic acid synthesis
rifamycins (rifampin (Rimactane)): inhibits DNA-dependent RNA polymerase
quinolones: inhibit gyrase
Antimetabolites
sulfonamides
trimethoprim (generic)
Some Nucleic Acid Analogs (Antivirals): inhibitors of viral replication
zidovudine (Retrovir, AZT, azidothymidine)
ganciclovir (DHPG, Cytovene)
vidarabine (Vira-A)
acyclovir (Zovirax)
Chambers, H.F and Sande, M.A. Antimicrobial Agents in,In, Goodman and Gillman's The Pharmacologial Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) TheMcGraw-Hill Companies, Inc.,1996, pp.1029-1030
Disease caused by bacteria and the the role of the host response in outcome of chemotherapeutic intervention.
Importance of Host Response
Host response as manifest in the inflammatory response is crucial for both the interruption resolution of the infection and for the basis of the infection's signs and symptoms.
The ability of effective antibiotic chemotherapy depends not only on appropriate selection of medication(s), dosage, and interval, but also on the host immune response.
Pier, G.B. Molecular Mechanism of Bacterial Pathogenesis., In Harrison's Principles of Internal Medicine (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1994, p. 592.
Disease Manifestations of Bacterial Disease
Disease manifestation of bacterial infection involves:
Colonization
Invasion: Bacterial invasion refers to the presence of bacteria in tissue sites normally sterile.
Examples:
Gram-negative rods in the blood stream result in septisemia and bacteremia without requiring endotoxin involvement
Pneumococcal pneumonia is due the growth of Streptococcus pneumoniae in the lung while bacterial endotoxins do not appear to play a role.
Disease that occurs after bactermia and invasion of the meninges by meningitis-producing bacteria (N. meningitidis, H. influenzae, E. coli, K1 and group B streptococci) is due to tissue destruction secondary to bacterial growth and host inflammation.
Toxin production and release
Toxin Elaboration
Clinicial manifestation of some bacterial infections are primarily due to toxin elaboration.
For example: Botulinum toxin: C. botulinum, Tetanus toxins: C. tetani, Diptheria toxin causes the disease due to infection with C. diphtheriae
Some specific aspects of bacterial disease are caused by elaborated toxins
Enterotoxins cause the diarrhea associated with E. coli, Salmonella, Shigella, Staphylococcus and V. cholerae.
Toxins involved in Toxic shock syndrome caused by Staphylococci, steptococci, P. aeruginosa and Bordatella: include: Toxic shock syndrome toxin (TSST), erythrogenic toxin, exotoxin A and pertussis toxin.
Staphylococcal enterotoxins, TSST-1 and streptococcal exotoxins have been classified as superantigens which are capable of inducing certain T cell proliferation without processing of the protein toxin by antigen-presenting cells.
This process involves, in part, the elaboration of IL-1 and TNF-alpha which may cause many clinical features seen in staphylococcal toxic shock syndrome, scarlet fever, streptococcal toxic shock syndrome.
Pier, G.B. Molecular Mechanism of Bacterial Pathogenesis., In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 855.
Endotoxins (lipid A portion of gram-negative LPS) may cause many clinical presentations seen in gram-negative bacterial sepsis: Toxins involve include: IL-1 and TNF-alpha--
Clinical presentations include:fever, intravascular coagulation, shock, and muscle proteolysis.
Pier, G.B. Molecular Mechanism of Bacterial Pathogenesis., In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 855.
Importance of Host Response
Host response as manifest in the inflammatory response is crucial for both interruption and infection resolution and the infection's signs and symptoms.
The ability of effective antibiotic chemotherapy depends not only on appropriate selection of medication(s), dosage, and interval, but also on the host immune response.
Pier, G.B. Molecular Mechanism of Bacterial Pathogenesis., In Harrison's Principles of Internal Medicine (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1994, p. 592.
Pharmacokinetic barriers that reduce the effectiveness of treatment
Introduction
Pharmacokinetic components include absorption, distribution, biotransformation (metabolism) and excretion.
Pharmacokinetic "profile" of antibacterial describes the drug concentration in tissues and serum as a function of time after administration.
The profile depends on the agent's absorption, distribution, biotransformation and excretion.
In therapeutics "trough" concentration (low) and "peak" concentrations (high) are important.
Pharmcokinetic information is used to establish dose and dosing intervals.
Absorption
Oral Therapy predominates for the following principal reasons: lower costs and fewer adverse effects
Another consideration, however, is that the oral route of administration is associated with a substantial range of bioavailabililty. For example, oral availability is only about 10% to 20% erythromycin estolate (Ilosone) and penicillin G, whereas bioavailability is about 100% for clindamycin (Cleocin), doxycycline (Vibramycin, Doryx) methonidazole, and trimethoprim (generic) sulfamethoxazole (Gantanol).
Bioavailability differences are NOT clinically important if the concentration of drug at the site of infection is sufficient to inhibit (bacteriostatic) or to kill (bacteriocidal).
Factors that can influence oral bioavailability include the presence of food in the digestive tract and drug interactions for example quinolones with metal cations.
Intramuscular
Administration by this route offers 100% bioavailable, but not widely used because of injection site pain can be usually ease of intravenous administration in the hospital inpatient setting.
Intravenous Administration:
Intravenous administration, however, would be appropriate if for example, oral agents proved ineffective, if there is a special concern about bioavailability, if larger doses are required relative to those typically obtained from oral dosing or because the bioavailability will be known to be 100%.
Distribution:
Antibacterial concentrations must exceed that required to inhibit bacterial growth (MIC).
Given that most infections are located outside the blood stream, the drug must distribute to those sites.
Drug concentration at most sites are similar to serum levels.
Some sites are "protected", however. these protected sites include the eye, prostate, and cardiac sites where there may be vegetative growth (e.g. around valves in a bacterial endocarditis setting)
High parentral doses may be required in these circumstances.
Poor efficacy may be related to adequate concentrations, but local unfavorable conditions.
For example, the activity of aminoglycosides is reduced in acidic pH, common at sites of infection. Biological constituants present in absesses may also inhibit the activity of antibacterials, thus requiring surgical dranage prior to efficacious therapy.
Archer,G.L. and Polk, R.E. Treatment and Prophylaxis of Bacterial Infections, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 860.
Mechanisms for chemotherapeutic drugs resistance
Bacterial resistance may occur because the drug does not reach its target site, drug is inactivated, or there is some sort of molecular alteration in the target itself, possibly due to mutation.
Resistance may occur because enzymes at or near the cell surface inactivate the antibiotic; the cell membrane is impermeable to the drug; there is an absence of aqueous channels (porins) through which the drug will reach the cell interior; there is a lack of a necessary transport system to support drug translocation; the transport mechanism is present but inoperative due to anaerobic metabolism; there are target site changes that results in reduced or absent antibacterial drug efficacy.
How Bacteria Acquire Resistance
Resistance may be acquired by vertical transfer, i.e. acquired by mutation and then passed to daughter cells
Mutations: Specific genetic mutations are the molecular basis for resistance to streptomycin (ribosomal mutation), to quinolones (DNA gyrase gene mutation) and to rifampin (Rimactane) (RNA polymerase gene mutation)
The mutation to rifampin (Rimactane) is an example of a single-step mutation: In this case E. coli or Staph. aureus exposure to rifampin results in highly resistant strain due to a point mutation in the RNA polymerase gene such that the polymerase protein no longer binds rifampin.
More usually, acquired by horizontal transfer of resistance factors from a donor cell, perhaps of a different species by transformation which involves the incorporation of DNA found free environment into the bacterial genome.
An example of this process is the basis of penicillin resistance in. pneumococci and Neisseria gonorrhoeae.
Penicillin-resistant pneumococci produce different PBPs (penicillin-binding proteins). These different PBPs exhibit relatively low affinity for penicillin compared to wild type pneumococci.
These different PBPs arise from integration of foreign DNA which were most likely from a closely related streptococcal strain into the PBP gene by a process of homologous recombination.
Transduction-based resistance occurs when a bacteriophage which includes bacterial DNA in its protein coat infects the bacteria. This bacterial DNA may contain a gene confiring resistance to antibacterial drugs.
Examples of this process:
Staphylococcus aureus strain resistance development to penicillin may occur by transduction (Some bacteriophages carry plasmids [extrachromosomal self-replicating DNA] that code for penicillinase
Other phages can transfer genes which confer resistance to tetracycline (Achromycin), erythromycin estolate (Ilosone), and chloramphenicol (Chloromycetin).
Conjugation is another important mechanism for single and multi-drug resistance development. In conjugation direct passage of resistance-confering DNA between bacteria proceeds by way of a bridge
The genetic material transfer in conjugation requires two elements: an R-determinant plasmid which codes for the resistance and a resistance-transfer factor (RTF) plasmid which contains the genes necessary for the bacterial conjugation process. Occasionally two plasmids join to form a complete R factor
Some genes that are responsible for resistance are located on transposons which can move from location to location within plasmid and bacterial genomes.
Conjugation mediated resistance is particularly important in gram-negative bacilli.
Enterococci may contain plasmids that spread resistance among gram-positive organisms
Vancomycin (Vancocin) resistance in enterococcal strains appears to occur as a result of the conjugation mechanism.
Conjugation is not a high efficiency mechanism for resistance development. Unfortunately, antibiotic use provides selection pressures which facilitate the elaboration of resistance bacteria. Furthermore, enteric bacteria carrying plasmids for multidrug resistance is now a worldwide, serious concern.
Resistance acquired by horizontal transfer can disseminate rapidly through the bacterial population by clonal spread as well as by continuing genetic material exchange between cells of the same or different susceptible strains.
Chambers, H.F and Sande, M.A. Antimicrobial Agents in,In, Goodman and Gillman's The Pharmacologial Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) TheMcGraw-Hill Companies, Inc.,1996, pp.1031.
Microbial Resistance and Specific Drugs
Resistance: ß-Lactams
Most common among several mechanisms by which bacteria develop resistance to ß-Lactam antibiotics is by elaboration of the enzyme ß-lactamase, which hydrolyzes the ß-lactam ring.
Beta-lactamase genes may be found in both gram-positive and gram-negative bacteria. Resistance may be reduced by agents which bind to some beta-lactamases. Examples of these drugs include clavulanic acid and sulbactam.
Another mechanism by which bacteria may develop resistance to beta-lactam antibiotics is by changes in penicillin-binding proteins (PBPs). These changes may occur either by mutation of existing PBP genes or more often by the acquisition of new PBP genes. For the latter case, unimportant example is staphylococcal resistance to methicillin (Staphcillin).
In addition to mutation of existing PBP genes, bacterial also acquiring new "pieces or segments" of PBP genes. This process appears important in resistance development for certain pneumococcal, gonococcal, and meningococcal strains)
Yet another mechanism is observed in gram-negative bacteria and follows from alteration of genes that code for certain outer membrane proteins (porins). The expression of altered porins reduce membrane permeability to penicillins. This process appears important in cephalosporin-resistance of Enterbacteriaceae and that of Pseudomonas species to ureidopenicillins.
Multiple resistance mechanisms can exist within the same bacterial cell.
Archer,G.L. and Polk, R.E. Treatment and Prophylaxis of Bacterial Infections, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 859.
Chloramphenicol (Chloromycetin) resistance:
This resistance occurs because of the formation of an acetylated chloramphenicol (Chloromycetin) derivative which is not biologically active.
A plasmid-encoded enzyme, chloramphenicol acetyltransferase catalyzes the acetyl group transfer which would otherwise not occur
Vancomycin (Vancocin) resistance is an important problem in antibiotic chemotherapy. For example, vancomycin (Vancocin)-resistant enterococci strains are worldwide.
The resistance mechanism involves transfer between cells and is plasmid mediated.
The specific alteration is a change in the peptidoglycan stem peptide which causes a loss of the vancomycin (Vancocin) binding target.
Often significant vancomycin (Vancocin) resistance is observed with enterococci strains all the same time most staphylococci aureus and staphylococci epidermis remain vancomycin (Vancocin) sensitive.
Resistance to tetracyclines:
The most common mechanism for gram-negative bacterial resistance follows from insertion of a plasmid-encoded active-efflux pump which translocates tetracycline (Achromycin) out of the cell.
For gram-positive bacteria, resistance may follow from the above mechanism (active efflux) or is a result of changes in the tetracycline ribosomal target site.
Aminoglycoside resistance:
The most common resistance mechanism is antibiotic inactivation by enzyme-mediated covalent bond modification. Modifications occur as a result of acetyl, adenyl or phosphate group transfer.
Enzymes which catalyze these group transfers and confer antibody resistance are plasmid localized.
As a consequence of these molecular modifications, the modified antibiotic becomes less active secondary to reduced transport and attenuated ribosomal target site binding.
Aminoglycoside-modifying enzymes occur in both gram-negative and gram-positive bacteria.
Mupirocin resistance: Resistance to this topical drug is due to alteration in the target site which is an isoleucine tRNA synthetase enzyme. Following modification, the enzyme no longer binds mupirocin (Bactriban)
Macrolides and Licosamides resistance. Antibiotic from these categories target gram-positive bacteria.
Resistance to these antibiotics result from plasmid-mediated ribosomal RNA methylation that interferes with antibiotic binding.
Specific antibiotic susceptible to this type of resistance include erythromycin, newer macrolides and clindamycin (Cleocin).
Quinolone-resistance:
Quinone resistance including resistance to newer fluoroquinolones has developed quickly in Staphylococcus and Pseudomonas strains.
The resistance mechanism involves a mutation in the drug target site, which is DNA gyrases. The mediated DNA gyrases are not susceptible to inhibition by quinolones.
Other resistance mechanisms involve in gram-negative strains, mutations in porins that cause the bacterial membrane to lose its permeability to the drug.in gram-positive organisms, resistance follows the development of the capability that enables the cell to actively pump out the drug from the cell.
Rifampin (Rimactane) resistance can rapidly develop as a result of target site mutations. The target in this case is RNA polymerase. Following mutation of the polymerase, rifampin (Rimactane) no longer binds.
Rapid strain resistance development has become a major limiting factor in rifampin (Rimactane) use in management of susceptible staphylococci thus requiring rifampin (Rimactane) to be combined with another antistaphylococcal drug.
Multiple Antibiotic Resistance Summary
It is increasingly common for one bacterium to be resistant to several antibacterial drugs.
Mechanisms:
Acquisition of multiple, unrelated resistance genes (several steps required)
Mutation in a single gene which results in resistance to unrelated drugs. (single step)
Bacteria resistant due to acquisition of new genes:
hospital-associated gram-negative bacteria
enterococci
staphylococci
community-acquired salmonellae strains
gonococci
pneumococci.
Single gene mutations: usually affecting porins of gram-negative bacteria involve:
ß-lactams
quinolones
tetracycline
chloramphenicol (Chloromycetin)
trimethoprim (generic)
Strains resistant to all known antibacterial drugs have been identified.
Archer,G.L. and Polk, R.E. Treatment and Prophylaxis of Bacterial Infections, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 859.
Clinical indications and rationale for the use of multiple drugs at the same time (combination chemotherapy)
Single Agent Chemotherapy
Single most specific drug is preferable if the infecting bacteria has been identified.
Administration of a single drug with a narrow spectrum of action is desirable because (a) alteration of normal flora is minimized (which in turn reduces the likelihood of overgrowth of resistant nosocomial bacteria (e.g. Candida albicans, enterococci, Clostridium difficile), (b) reduces toxicity which may be associated with multiple drug regimens and (c) reduces cost.
Archer,G.L. and Polk, R.E. Treatment and Prophylaxis of Bacterial Infections, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 862.
Combination Chemotherapy
Combination chemotherapy may be warrented to:
Decrease the likelihood of emergence of resistant mutants. A single agent will be effective against sensitive organisms, but not against those that have developed a mutated "target" site, which is no longer susceptible or has diminished susceptibility to the drug. In this case the single drug will select out the mutant, resistant strain. This effect is more likely when the concentration of the antibacterial agent approximates the MIC (minimum inhibitory concentration).
Examples:
rifampin (Rimactane) : staphylococci
ciprofloxacin (Cipro): staphylococci and Pseudomonas.
imipenem: Pseudomonas
aminoglycosides: staphylococci
A second agent, which acts by a different mechanism, may prevent the emergence of the resistant strain (e.g. impenem + aminoglycoside for systemic Pseudomonas).
To take advantage of additive/synergistic action against some bacteria. Synergistic or additive activity occurs if the MIC or MBC of each agent is lowered in the presence of the other. Accordingly, each drug is more efficacious when combined with the other. (1) Certain ß-lactam-aminoglycoside combinations are effective against enterococci, viridans streptococci, and P. aeruginosa. (2) Combination of trimethoprim-sulfamethoxazole (Bactrim) is effective against many enteric gram negative bacteria. (3) Most other combinations are not clinically surperior compared to administration of the more efficacious single drug component.
Some combinations are less effective than a single agent: penicillin plus tetracycline (Achromycin) against pneumonococci.
To provide therapy when multiple pathogens may be or are known to be present . If a mixture of pathogens is thought to be present and/or the patient is critically ill, combination therapy may be warrented. [Multiple Pathogens may be present in intra-abdominal or brain abscesses and limb infection in diabetic patients; in critical illness fevers in neutropenic patients, acute aspiration pneumonia (oral flora) by hospitalized patients, septic shock or sepsis syndrome. However, monotherapy should be started if a single infecting bacterium that can be appropriately treated with a single drug has been identified
Archer,G.L. and Polk, R.E. Treatment and Prophylaxis of Bacterial Infections, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 862.
Rationale for chemoprophylaxis
Chemoprophylaxis
A manifestation of antibiotic misuse is that 30% to 50% of the time, the antibiotic is prescribed to prevent rather treat an infection.
Prophylaxis is more likely to be effective if a single, effective, nontoxic drug is used to prevent infection by a specific organism or to eliminate a recently established infection.
Examples of effective chemoprophylaxis:
Penicillin G prevents infection by group-A streptococci.
Intermittent use of trimethoprim (generic) sulfamethoxazole (Gantanol) prevents recurrent urinary tract infections
Prevention of endocarditis in patients with valvular heart lesions who are to undergo a surgical procedure.
The most extensive use of chemoprophylaxis is prevention of wound infections following surgery.
Chambers, H.F and Sande, M.A. Antimicrobial Agents in,In, Goodman and Gillman's The Pharmacologial Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) TheMcGraw-Hill Companies, Inc.,1996, pp.1049-1050
Appropriate and Inappropriate Uses of Chemotherapy
Appropriate Use
Before the organism is identified: either combination therapy or a single broad spectrum agent may be used.
After the organism is identified, a low-toxicity regimen with a narrow-spectrum drug is indicated.
Selection of the drug should be goverened by its selectivity for the most likely involved bacteria and its toxicity.
First decide if an antibiotic is indicated since antibiotics may be toxic. Inappropriate use may hinder diagnosis, and can result in development of resistant bacterial strains
Some Clinical Issues
Optimal empirical treatment requires knowledge of the antibiotic sensitivity of the organisms which is most likely causing the infection.
Assessment with Gram's stain and other tests must be used to narrow the list of pathogens.
In life threatening situations, the selection of a single narrow-spectrum agent may not be possible and broad coverage would be indicated until a definitive identification is possible.
Chambers, H.F and Sande, M.A. Antimicrobial Agents in,In, Goodman and Gillman's The Pharmacologial Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) TheMcGraw-Hill Companies, Inc.,1996, pp.1054-1055
Inappropriate Uses
Treatment of Untreatable Infections:
The infection is viral.
Antimicrobial treatment of measles, mumps and 90% of upper respiratory infections are inappropriate.
Treatment of fever of unknown origin:
Antimicrobials are not antipyretic agents.
Pyrexia of short duration, without localizaing signs, is most likely due to viral infection.
Three infections may be associated with prolonged fever:
tuberculosis
hidden intra-abdominal abscesses
infective endocarditis.
other causes: cancer metabolic disorders hepatitis atypical rheumatoid arthritis
Improper dosage:
Some drugs, such as the aminoglycosides, are frequently administered at subtherapeutic dosages because of concern about toxicity.
Clinical treatment failure and selection of resistant strains may result.
Inappropriate Dependence on Chemotherapy Alone:
Some disorders require both chemotherapy and a surgical procedure, especially if significant amount of necrotic tissue is present.
Example : Pneumonia in a patient with empyema (accumulation of pus) may be effectively manage following drainage
Lack of Adquate Bacteriological Information:
About one-half of antimicrobial therapy is given to hospitalized patients without support from microbiological data. [clinical judgment alone];
Antimicrobial therapy must be individualized, not administered based on prescribing habit alone.
Chambers, H.F and Sande, M.A. Antimicrobial Agents in,In, Goodman and Gillman's The Pharmacological Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) TheMcGraw-Hill Companies, Inc.,1996, pp.1054-1055
Wednesday, July 8, 2009
Chemical aspects of drugs
Drug shape
The shape of the drug is an important factor in defining the nature of the drug-receptor interaction. The three-dimensional shape of the drug is thought to interact with a complementary structural binding region of the receptor, typically a protein. The specific nature of the interaction defines whether the drug acts as an agonist promoting a change in cellular function or as an antagonist which blocks the receptor usually resulting in no direct biological effect.
For example, let's consider acetylcholine or a synthetic analogue bethanechol (Urecholine). Interaction of these molecules with receptor (nicotinic or muscarinic cholinergic receptor) causes a physiological response -- a decrease in heartbreak for instance. By contrast, a muscarinic antagonist such as atropine may bind even more tightly than acetylcholine to muscarinic receptor but causes no direct effect. However, following administration of antagonist a biological response may be observed as a result of receptor blockade.
A clinical example would be bradycardia following acute myocardial infarction. Bradycardia in this context might be due to excessive parasympathetic (cholinergic) tone and might cause unacceptably low cardiac output or predispose tomore serious arrhythmias. Administration of atropine, by blocking the muscarinic receptor blunts the action of acetylcholine and accordingly may reverse bradycardia.
Now let's consider the specific example,acetylcholine, as the 2D planar structure:
On the left side of the molecule note the quaternary (always positively charged) Nitrogen, which is part of the choline component of acetylcholine. The synthesis of acetylcholine proceeds by combination of choline and acetate (as Acetyl-CoA)-see below
Now let's examine the 3-D structure of choline (pressing and holding down your left mouse button allows you to rotate the choline 3-D interactive structure). By convention, nitrogen atoms are blue, oxygen red and carbon gray.
Similarly we can examine interactively the 3-D structure of acetylcholine:
Note above the presence of an "ester" linkage [O in red] between the choline moiety and the seal group.
This ester bond is susceptible to hydrolysis, i.e. breakage which may be catalyzed by esterases (acetylcholinesterase is an example).
Acetycholine:
Although acetylcholine is depicted as a "static" molecule in terms of internal rotation,, acetylcholine and many other drugs exhibit free rotation around internal bonds.
For acetylcholine,tau1, tau2, tau3, represent torsion angles and refer to the degree of twist around these bonds of free rotation
Specific additional analysis is required to determine which three-dimensional form of acetylcholine appears to be preferred for binding to the cholinergic receptor. The configuration of acetylcholine and solution is quite different than the configuration when bound to the nicotinic cholinergic receptor (using two-dimensional NMR to estimate bond angles)
Above figures adapted from Principles of Drug Action: The Basis of Pharmacology, Third Edition, edited by William . B. Pratt and Palmer Taylor, Churchill Livingston, New York, 1990. pp 20-23. Above Acetylcholine conformation figure -- original work: Behling, RW, Yamane T, Gavon G, Jelinski LW: Conformation of Acetylcholine Bound to the Nicotinic Acetylcholine Receptor. Proc Natl Acad Sci USA 85:6721, 1988.
Some short-acting pharmacological agents are in fact short-acting because they are rapidly hydrolyzed at an ester linkage.
Ester-type local anesthetics
Esmolol (Brevibloc)
Remifentanil (Ultiva).
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The biological action acetylcholine is terminated by hydrolysis, catalyzed by the enzyme acetylcholinesterase: The overall reaction is shown below --
Acetylcholinesterase itself is a large, complex protein which has its primary catalytic function the extremely rapid hydrolysis of the neurotransmitter acetylcholine.
Acetylcholinesterase
The image below illustrates the relationship between the very small molecule, acetylcholine, and its specific interaction within the very large molecule, acetylcholinesterase.
This image illustrates how the neurotransmitter acetylcholine represented above the in ball-and-stick form is recognized by specific amino acids within acetylcholinesterase's active site.
The positive charge of acetylcholine (due to the permanently positive quaternary nitrogen) interacts with tryptophan-84 (Trp-84) and phenylalanine-330 (Phe-330), through cationic (+ charged)- π-electron interactions}
This part of the acetylcholinesterase molecule is referred to as the "aromatic gorge"
The negatively charged amino acid, glutamatic acid-199 (Glu-199) is thought to interact with acetylcholine through ionic-type interactions
The shape of the drug is an important factor in defining the nature of the drug-receptor interaction. The three-dimensional shape of the drug is thought to interact with a complementary structural binding region of the receptor, typically a protein. The specific nature of the interaction defines whether the drug acts as an agonist promoting a change in cellular function or as an antagonist which blocks the receptor usually resulting in no direct biological effect.
For example, let's consider acetylcholine or a synthetic analogue bethanechol (Urecholine). Interaction of these molecules with receptor (nicotinic or muscarinic cholinergic receptor) causes a physiological response -- a decrease in heartbreak for instance. By contrast, a muscarinic antagonist such as atropine may bind even more tightly than acetylcholine to muscarinic receptor but causes no direct effect. However, following administration of antagonist a biological response may be observed as a result of receptor blockade.
A clinical example would be bradycardia following acute myocardial infarction. Bradycardia in this context might be due to excessive parasympathetic (cholinergic) tone and might cause unacceptably low cardiac output or predispose tomore serious arrhythmias. Administration of atropine, by blocking the muscarinic receptor blunts the action of acetylcholine and accordingly may reverse bradycardia.
Now let's consider the specific example,acetylcholine, as the 2D planar structure:
On the left side of the molecule note the quaternary (always positively charged) Nitrogen, which is part of the choline component of acetylcholine. The synthesis of acetylcholine proceeds by combination of choline and acetate (as Acetyl-CoA)-see below
Now let's examine the 3-D structure of choline (pressing and holding down your left mouse button allows you to rotate the choline 3-D interactive structure). By convention, nitrogen atoms are blue, oxygen red and carbon gray.
Similarly we can examine interactively the 3-D structure of acetylcholine:
Note above the presence of an "ester" linkage [O in red] between the choline moiety and the seal group.
This ester bond is susceptible to hydrolysis, i.e. breakage which may be catalyzed by esterases (acetylcholinesterase is an example).
Acetycholine:
Although acetylcholine is depicted as a "static" molecule in terms of internal rotation,, acetylcholine and many other drugs exhibit free rotation around internal bonds.
For acetylcholine,tau1, tau2, tau3, represent torsion angles and refer to the degree of twist around these bonds of free rotation
Specific additional analysis is required to determine which three-dimensional form of acetylcholine appears to be preferred for binding to the cholinergic receptor. The configuration of acetylcholine and solution is quite different than the configuration when bound to the nicotinic cholinergic receptor (using two-dimensional NMR to estimate bond angles)
Above figures adapted from Principles of Drug Action: The Basis of Pharmacology, Third Edition, edited by William . B. Pratt and Palmer Taylor, Churchill Livingston, New York, 1990. pp 20-23. Above Acetylcholine conformation figure -- original work: Behling, RW, Yamane T, Gavon G, Jelinski LW: Conformation of Acetylcholine Bound to the Nicotinic Acetylcholine Receptor. Proc Natl Acad Sci USA 85:6721, 1988.
Some short-acting pharmacological agents are in fact short-acting because they are rapidly hydrolyzed at an ester linkage.
Ester-type local anesthetics
Esmolol (Brevibloc)
Remifentanil (Ultiva).
return to Table of Contents
The biological action acetylcholine is terminated by hydrolysis, catalyzed by the enzyme acetylcholinesterase: The overall reaction is shown below --
Acetylcholinesterase itself is a large, complex protein which has its primary catalytic function the extremely rapid hydrolysis of the neurotransmitter acetylcholine.
Acetylcholinesterase
The image below illustrates the relationship between the very small molecule, acetylcholine, and its specific interaction within the very large molecule, acetylcholinesterase.
This image illustrates how the neurotransmitter acetylcholine represented above the in ball-and-stick form is recognized by specific amino acids within acetylcholinesterase's active site.
The positive charge of acetylcholine (due to the permanently positive quaternary nitrogen) interacts with tryptophan-84 (Trp-84) and phenylalanine-330 (Phe-330), through cationic (+ charged)- π-electron interactions}
This part of the acetylcholinesterase molecule is referred to as the "aromatic gorge"
The negatively charged amino acid, glutamatic acid-199 (Glu-199) is thought to interact with acetylcholine through ionic-type interactions
Thursday, May 28, 2009
A Subscription to Clinical Pharmacology Now Gives You a Powerful New Option
It's on the fundamental principle of providing healthcare professionals with timely, accurate, clinically-relevant drug data during the decision-making process - where and when it's needed most - that Gold Standard's product, Clinical Pharmacology, was conceived more than a decade ago, and what guides its product evolution today. A pioneer in the development and implementation of electronic drug information databases and solutions, Gold Standard continues to lead the way in the industry. And because we've made it our mission to ensure that Clinical Pharmacology not only meets, but exceeds, our customers' and their patients' needs and expectations, we're very excited to now offer you an even better, new and improved Clinical Pharmacology.
Maintaining the Gold Standard in Drug Information - A New Look!Quicker, Simpler, User-Friendly Navigation!Additional Content!
Still clinically-relevant, peer-reviewed and updated continuously, Clinical Pharmacology is now even smarter, faster, and easier to use! We've completely redesigned its user interface and functionality, making it extremely intuitive and easy for you to get to the information you need.
Easy-to-Use Search Dashboard/Control Panel
This new Clinical Pharmacology feature enables you to easily search for information, start reports, go to patient education, or other resources all from one place. Each area is grouped together in convenient drop-down menus, so that you can see at a glance exactly what information and tools are contained under each menu - one click takes you where you need to go.
All-Inclusive Search Result/Navigation Page
This "all in one" page allows you to quickly access numerous pieces of information and features related to a monograph or product - look at any monograph section, begin a report, select MedCounselor drug information sheets, or view products. Our new monograph navigation is effortless - drop-down lists provide links from key terms to content discussions.
Quick Drug IDentifier
Our Drug IDentifier feature is quickly accessible and simpler to use than ever before - just "click and go" to be on your way to accurately identifying unknown tablets and capsules.
Enhanced Drug Product Information
Clinical Pharmacology's drug product information now offers even more qualitative and detailed data. Tired of dealing with the headaches caused by manufacturers changing the color, shape or markings of a drug? Clinical Pharmacology provides details for BOTH the drug's new and previous appearances, making it easy for you to keep track of existing supplies, as well as counsel patients when the medication they've been taking suddenly has a "new look".
MedGuides Available
The FDA has significantly increased the number of prescriptions that must be dispensed with a MedGuide, now including a number of large drug classes that account for millions of prescriptions. Special formatting requirements have made it even more difficult for pharmacies to utilize MedGuides within workflow systems. Clinical Pharmacology provides a solution, as it now includes all publicly available MedGuides in their proper format and structure.
Clinical Pharmacology's Content and Features are Presented in 4 Convenient Main Sections
Reports
All report features are grouped together in one, convenient place - instantly run multi-drug interaction reports with lifestyle factors and severity rankings (available in healthcare professional and consumer versions), product comparison reports to find comparable products based on ingredients and/or therapeutic use, adverse reaction reports, clinical comparison reports, IV compatibility reports, and patent reports.
Find/List
Easily find a monograph by single or multiple criteria, such as indications, adverse reactions, contraindications/precautions, classification, manufacturer, or NDC. Plus, view specialized lists in just seconds, including products with MedGuides or monographs with boxed warnings (i.e., Black Box warnings).
Patient Education
Located in its own section, updated, and newly named "MedCounselor Sheets ", Clinical Pharmacology's patient drug information can be easily accessed from the Patient Education drop-down menu, and from within a monograph - a quick click displays all available MedCounselor sheets that apply to that monograph. It's all at your fingertips.
Resource Center
A great collection of helpful and valuable reference information, you'll love our new Resource Center, where you can take advantage of updated and expanded lab references, including pediatric ranges; pharmaceutical manufacturer/distributor contact information; links to drug class overviews; and links to other drug/disease information solutions from Gold Standard and our parent company, Elsevier, a world-leading publisher of scientific, technical and medical information products and services.
A Complete "All in One " Reference and Chosen Market Leader in Frontline Drug Information
Clinical Pharmacology leverages 21st century technology to deliver real-time drug information, efficient clinical tools, and multiple delivery formats - empowering healthcare professionals with a current, reliable solution that's unparalleled in the marketplace. Written by healthcare professionals for healthcare professionals, Clinical Pharmacology is so comprehensive, so concise, and so easy to navigate and use, it's a must have for any healthcare venue. It is the primary drug information and medication management resource of the majority of the country's largest retail pharmacy chains and consultant pharmacy corporations, many U.S. pharmacy and medical schools, over 1,000 hospitals, well-known health information websites, and by tens of thousands of healthcare professionals and consumers worldwide.
In-depth Coverage and a Complete Array of Clinical Support Tools Boost Productivity and Enhance Patient Care
In today's world where patient treatment is becoming increasingly more complex and healthcare professionals must stay current with the rapid advancement of new therapies, it's more important than ever that you have a strong, reliable drug information resource you can depend on. As healthcare professionals ourselves, we understand better than anyone that it's all about balancing the need for "quick answers" with "comprehensiveness" to ensure "accurate content" to allow for "informed decisions". That's what Clinical Pharmacology is all about. Learn more about Clinical Pharmacology's content and tools, by clicking on any item below:
Monographs
Product Identification
Drug Class Overviews
Product Information
Find (Search) Capabilities
Patient Education
Reports
IV Compatibility by Trissel's™2
We Deliver Your Drug Information the Way You Need It - Choose from a Variety of Formats
Clinical Pharmacology Internet: Hosted by Gold Standard, our online format includes complete access to Clinical Pharmacology's features and functionality with real-time content updates - IP authentication is also available via this format
Clinical Pharmacology Intranet: Download and install files locally and provide access to Clinical Pharmacology across your organization's internal Intranet system
Clinical Pharmacology CD-ROM: The same features and functionality of Clinical Pharmacology Internet on an easy-to-navigate, Windows-based CD-ROM - updated quarterly
Clinical Pharmacology Content Licensing and Data Integration: The Clinical Pharmacology database offers a variety of unique licensing options for integration into healthcare websites, disease management software, practice management and prescription benefit management systems, or other medical applications - available for both clinicians and consumers. Contact us at 1-800-375-0943, 813-258-4747 or email sales@goldstandard.com to request additional information.
Clinical Pharmacology OnHand: Available for Palm and Pocket PC and updated daily, Clinical Pharmacology OnHand is an abridged, yet comprehensive, version of Clinical Pharmacology Internet's drug content and drug interactions reporting tool. Operate at maximum efficiency, check for clinical problems on-the-go, and always stay current! Other Clinical Pharmacology OnHand products, available as stand-alone or as companion modules, include:
Drug IDentifier - instantly and easily identify tablets and capsules by their marking, shape and/or color
IV Compatibility Alert - accurately check the compatibility of two or more intravenous products and/or solutions when mixed in solution or a syringe, or via a Y-site administration, in just seconds
Learn more about Clinical Pharmacology OnHand.
Take Advantage of Additional Valuable Gold Standard Offerings and Services to Build the Ultimate, Online, Integrated Drug, Disease, and Medical Information Solution
Clinical Pharmacology provides customers with exceptional value in actionable content, tools, features, delivery mechanisms, time-savings and cost-savings. We have a complete line of products, services, and solutions dedicated to successfully fulfilling your clinical workflow and patient care needs. Build your Clinical Pharmacology Internet subscription your way by adding these online offerings:
Clinical Calculators - ACLS and PALS, general dosing, drug dosing, dosage conversion, serum electrolyte adjustment, IV rate, and pharmacy compounding calculators.
Global Drug Name Directory - international brand and generic drug product names, linked to the U.S. equivalent monograph found in Clinical Pharmacology.
Krames Consumer Disease Information - patient education handouts, in English and Spanish, with engaging visuals and basic care instructions for medical conditions healthcare professionals deal with daily. Learn more.
PIER - Physicians' Information and Education Resource, evidence-based medicine guidelines from the American College of Physicians.
FormChecker - formulary management and pharmacy communication system.
ToxED - the clinician's toxicology information resource.
FirstCONSULT - an evidence-based clinical information system covering the latest evaluation, diagnosis, management, outcomes and prevention.
MDConsult - a clinical reference, combining leading medical reference books, full text medical journals, MEDLINE, and more in a searchable format.
Maintaining the Gold Standard in Drug Information - A New Look!Quicker, Simpler, User-Friendly Navigation!Additional Content!
Still clinically-relevant, peer-reviewed and updated continuously, Clinical Pharmacology is now even smarter, faster, and easier to use! We've completely redesigned its user interface and functionality, making it extremely intuitive and easy for you to get to the information you need.
Easy-to-Use Search Dashboard/Control Panel
This new Clinical Pharmacology feature enables you to easily search for information, start reports, go to patient education, or other resources all from one place. Each area is grouped together in convenient drop-down menus, so that you can see at a glance exactly what information and tools are contained under each menu - one click takes you where you need to go.
All-Inclusive Search Result/Navigation Page
This "all in one" page allows you to quickly access numerous pieces of information and features related to a monograph or product - look at any monograph section, begin a report, select MedCounselor drug information sheets, or view products. Our new monograph navigation is effortless - drop-down lists provide links from key terms to content discussions.
Quick Drug IDentifier
Our Drug IDentifier feature is quickly accessible and simpler to use than ever before - just "click and go" to be on your way to accurately identifying unknown tablets and capsules.
Enhanced Drug Product Information
Clinical Pharmacology's drug product information now offers even more qualitative and detailed data. Tired of dealing with the headaches caused by manufacturers changing the color, shape or markings of a drug? Clinical Pharmacology provides details for BOTH the drug's new and previous appearances, making it easy for you to keep track of existing supplies, as well as counsel patients when the medication they've been taking suddenly has a "new look".
MedGuides Available
The FDA has significantly increased the number of prescriptions that must be dispensed with a MedGuide, now including a number of large drug classes that account for millions of prescriptions. Special formatting requirements have made it even more difficult for pharmacies to utilize MedGuides within workflow systems. Clinical Pharmacology provides a solution, as it now includes all publicly available MedGuides in their proper format and structure.
Clinical Pharmacology's Content and Features are Presented in 4 Convenient Main Sections
Reports
All report features are grouped together in one, convenient place - instantly run multi-drug interaction reports with lifestyle factors and severity rankings (available in healthcare professional and consumer versions), product comparison reports to find comparable products based on ingredients and/or therapeutic use, adverse reaction reports, clinical comparison reports, IV compatibility reports, and patent reports.
Find/List
Easily find a monograph by single or multiple criteria, such as indications, adverse reactions, contraindications/precautions, classification, manufacturer, or NDC. Plus, view specialized lists in just seconds, including products with MedGuides or monographs with boxed warnings (i.e., Black Box warnings).
Patient Education
Located in its own section, updated, and newly named "MedCounselor Sheets ", Clinical Pharmacology's patient drug information can be easily accessed from the Patient Education drop-down menu, and from within a monograph - a quick click displays all available MedCounselor sheets that apply to that monograph. It's all at your fingertips.
Resource Center
A great collection of helpful and valuable reference information, you'll love our new Resource Center, where you can take advantage of updated and expanded lab references, including pediatric ranges; pharmaceutical manufacturer/distributor contact information; links to drug class overviews; and links to other drug/disease information solutions from Gold Standard and our parent company, Elsevier, a world-leading publisher of scientific, technical and medical information products and services.
A Complete "All in One " Reference and Chosen Market Leader in Frontline Drug Information
Clinical Pharmacology leverages 21st century technology to deliver real-time drug information, efficient clinical tools, and multiple delivery formats - empowering healthcare professionals with a current, reliable solution that's unparalleled in the marketplace. Written by healthcare professionals for healthcare professionals, Clinical Pharmacology is so comprehensive, so concise, and so easy to navigate and use, it's a must have for any healthcare venue. It is the primary drug information and medication management resource of the majority of the country's largest retail pharmacy chains and consultant pharmacy corporations, many U.S. pharmacy and medical schools, over 1,000 hospitals, well-known health information websites, and by tens of thousands of healthcare professionals and consumers worldwide.
In-depth Coverage and a Complete Array of Clinical Support Tools Boost Productivity and Enhance Patient Care
In today's world where patient treatment is becoming increasingly more complex and healthcare professionals must stay current with the rapid advancement of new therapies, it's more important than ever that you have a strong, reliable drug information resource you can depend on. As healthcare professionals ourselves, we understand better than anyone that it's all about balancing the need for "quick answers" with "comprehensiveness" to ensure "accurate content" to allow for "informed decisions". That's what Clinical Pharmacology is all about. Learn more about Clinical Pharmacology's content and tools, by clicking on any item below:
Monographs
Product Identification
Drug Class Overviews
Product Information
Find (Search) Capabilities
Patient Education
Reports
IV Compatibility by Trissel's™2
We Deliver Your Drug Information the Way You Need It - Choose from a Variety of Formats
Clinical Pharmacology Internet: Hosted by Gold Standard, our online format includes complete access to Clinical Pharmacology's features and functionality with real-time content updates - IP authentication is also available via this format
Clinical Pharmacology Intranet: Download and install files locally and provide access to Clinical Pharmacology across your organization's internal Intranet system
Clinical Pharmacology CD-ROM: The same features and functionality of Clinical Pharmacology Internet on an easy-to-navigate, Windows-based CD-ROM - updated quarterly
Clinical Pharmacology Content Licensing and Data Integration: The Clinical Pharmacology database offers a variety of unique licensing options for integration into healthcare websites, disease management software, practice management and prescription benefit management systems, or other medical applications - available for both clinicians and consumers. Contact us at 1-800-375-0943, 813-258-4747 or email sales@goldstandard.com to request additional information.
Clinical Pharmacology OnHand: Available for Palm and Pocket PC and updated daily, Clinical Pharmacology OnHand is an abridged, yet comprehensive, version of Clinical Pharmacology Internet's drug content and drug interactions reporting tool. Operate at maximum efficiency, check for clinical problems on-the-go, and always stay current! Other Clinical Pharmacology OnHand products, available as stand-alone or as companion modules, include:
Drug IDentifier - instantly and easily identify tablets and capsules by their marking, shape and/or color
IV Compatibility Alert - accurately check the compatibility of two or more intravenous products and/or solutions when mixed in solution or a syringe, or via a Y-site administration, in just seconds
Learn more about Clinical Pharmacology OnHand.
Take Advantage of Additional Valuable Gold Standard Offerings and Services to Build the Ultimate, Online, Integrated Drug, Disease, and Medical Information Solution
Clinical Pharmacology provides customers with exceptional value in actionable content, tools, features, delivery mechanisms, time-savings and cost-savings. We have a complete line of products, services, and solutions dedicated to successfully fulfilling your clinical workflow and patient care needs. Build your Clinical Pharmacology Internet subscription your way by adding these online offerings:
Clinical Calculators - ACLS and PALS, general dosing, drug dosing, dosage conversion, serum electrolyte adjustment, IV rate, and pharmacy compounding calculators.
Global Drug Name Directory - international brand and generic drug product names, linked to the U.S. equivalent monograph found in Clinical Pharmacology.
Krames Consumer Disease Information - patient education handouts, in English and Spanish, with engaging visuals and basic care instructions for medical conditions healthcare professionals deal with daily. Learn more.
PIER - Physicians' Information and Education Resource, evidence-based medicine guidelines from the American College of Physicians.
FormChecker - formulary management and pharmacy communication system.
ToxED - the clinician's toxicology information resource.
FirstCONSULT - an evidence-based clinical information system covering the latest evaluation, diagnosis, management, outcomes and prevention.
MDConsult - a clinical reference, combining leading medical reference books, full text medical journals, MEDLINE, and more in a searchable format.
Saturday, May 2, 2009
The Importance of Microbiology in the Contamination Control Plan for Aseptic, Terminally Sterilized and Non-sterile Manufacturing
Introduction
The development of a contamination control program is critical to the effort to get a new facility qualified, and to maintain the facility in a state of control once qualified. The design and successful execution of a contamination control program requires a plan. The creation of a specific document allows the company philosophy, goals, and expectations to be formalized and agreed to by all parties. It also provides the goals and metrics by which the state of control for the facility can be measured in the annual review. The business reasons for this are obvious in terms of reduced regulatory risk and reduction of rejected/recalled batches (Lowry 2001).
This plan is important no matter what type of facility is being developed. Although it is most frequently used in the Quality plan for commissioning an aseptic facility, this is also important and should be used for commissioning and controlling facilities using terminal sterilization, and for non-sterile manufacturing facilities.
Why be concerned with contamination control in a nonsterile manufacturing facility? In many ways contamination control is more of a concern in a non-sterile facility than in sterile product production facilities. The sterile production facility knows there is a problem with contamination and cross-contamination of batches, the non-sterile facility has a great temptation to belief they are not touched by these issues. This can lead to an extremely cavalier attitude about contamination control by the operators and management. The non-sterile manufacturer is responsible for all aspects of his product, including any objectionable organisms present (Sutton, 2006) as described in a recent newsletter (PMF Newsletter v12 n7).
The API manufacturer is also concerned with contamination control. The FDA has explicit instruction on this score (FDA 1998) out of CBER. The EMEA guidance on API manufacture also includes guidance on control of bioburden and cross-contamination of batches (EMEA 2000).
This essay will not be able to provide more than an overview of issues in the space available this month. However, it is hoped that the need for an adequate contamination control plan for a facility will be made clear, and the beginnings of the content of such a plan explained. The interested reader is referred to the articles listed in the “References” and the “Further Readings” sections.
Scope
The Contamination Control Plan should be developed as part of the facility commissioning effort. As such, there will be four distinct phases of the facility operations that will need to be addressed:
Commissioning and initial start-up
Ongoing Operations
Shut-down for regular maintenance
Start-up after scheduled shut-down.
These phases will not have the same level of contamination control. In fact, the third and fourth phases may well have different levels of control to be addressed. A good plan will discuss the concerns specific to each of these phases.
This program, and the protocol governing the program, are essential documents useful in documenting the rationale and methods used to accomplish three tasks:
Minimizing the bioburden throughout the manufacturing processes
Minimizing the level of batch residual cross-over contamination
Minimizing the level of cleaning material residual contamination
As the SME (Subject Matter Expert) in microbiology, we will be most heavily involved in the first of these three tasks, minimizing bioburden. However, all three will be discussed (at least briefly) in this essay for context.
Minimizing Bioburden
Validated methods
All measures of bioburden in a facility will be indirect. We cannot count bacterial cells on a surface or in the air. We must transfer the microorganisms to an agar plate (or some other mechanism) and count colony forming units. If we make the assumption that the transfer of microorganisms from the air or from a surface to agar is consistent, then we can use these numbers to estimate trends over time. This assumes that the nutrient agar is capable of growing the microorganisms to visible colonies. As residual disinfectant on a surface may impede the growth of microorganisms, neutralizers are frequently incorporated into the growth media (Dey-Engley agar, MCTA, etc.). All sampling methods must be validated for the conditions of use.
The facility should be disinfected regularly using validated sanitizers and sporicides. The contamination control plan should describe the methods for testing and rationale for acceptance of materials to be used in the ongoing program of disinfection. The plan should ideally describe the in vitro or laboratory tests to evaluate the sanitizers, including the identification of the most resistant microorganisms found in the facility as well as the most difficult-to-disinfect materials in the facility. This is also where the method for on-going evaluation of the sanitizers based on environmental monitoring data will be recorded. The choice of disinfection regimens should be reevaluated annually, and the contamination control plan should describe how this evaluation will occur.
Know the enemy
A successful contamination control program is geared to providing the most useful information on the microorganisms present while at the same time showing some fiscal responsibility. The FDA aseptic processing guidance document recommends genetic identification of all organisms isolated from the manufacturing environment on a regular basis. (FDA, 2004) This is a laudable goal, but few of us have anything near the required budget to accomplish this task, and in all honesty it is reasonable to wonder if it is really necessary. The numbers of CFU from validated sites (viable air and surface, non-viable) is sufficient to provide a measure of the state of control of the facility. However, periodic cataloging of the resident microflora will provide you with a good check on the continued effectiveness of the disinfectants in use. Shifts of bioburden to spore forming microorganisms will be strong evidence of the need for use of a sporicidal agent. Occasionally, this effort will also pick up shifts among non-spore-forming organisms – this is not due to “resistance” but rather ecological shifts towards species more naturally resistant to the disinfectant in use.
Control incoming bioburden
The first step in any control program is to control contamination at the very beginning of the process. This includes raw materials (excipients, API, water, etc) and the primary containers. All materials should be tested for incoming bioburden against documented acceptance criteria. Part of the incoming bioburden will also be any water used as an excipient to the process. A good guide for the water bioburden is the EMEA guidance on the subject (EMEA 2002).
Appropriate gowning
The gowning methods and materials are of critical importance to minimization of contamination. Although most attention is placed on aseptic gowning procedures, the appropriate use of gowning precautions will be a great boon to most non-sterile manufacturing facilities as well. All personnel should be well-trained in appropriate gowning practice and behavior. The contamination control plan should describe the rationale for the level of gowning chosen, the frequency of gown cleaning, behavior and the acceptable gown materials for the type of manufacturing process.
Training
Operator training is critical to contamination control. No supervisor can be present at all locations at all times. Each operator must be aware of his or her role in contamination control and how to minimize the risk to batch integrity. The PDA has published a technical report that speaks to some of these training requirements from the microbiological perspective (PDA 2001).
Controlled Environments
Control and monitoring of the environment is another critical element of the contamination control plan. Large portions of this can be addressed by the corporate Environmental Monitoring Master Plan (which provides rationale and consistency for a single EM philosophy across the different facilities of the corporation) or the site Environmental Master Plan (which provides consistency and detailed instruction for the various manufacturing buildings at a given site). However, the Contamination Control Plan should cite the relevant documents and their role in contamination control. Those interested in more on environmental monitoring should refer to the PDA’s treatment of the subject for a good overview (PDA 2001).
The appropriate Environmental Monitoring (EM) plan for non-sterile manufactures and for API manufacturers is not well-defined from a regulatory sense. There are no strong recommendations such as those seen for the environmental monitoring of aseptic facilities; however the absence of regulatory guidance is not the same thing as the absence of need for the activity. EM is useful for determining the state of control of the facility (not so much, perhaps an indicator of the finished product quality) and so is an important part of the monitoring program for all manufacturers.
Well-defined and Understood Manufacturing Processes
The manufacturing process should be evaluated for its potential to limit or eliminate bioburden. The two common methods for performing this is either a HACCP-type (Jahnke and Kuhn 2003) or a FMEA approach. The use of organic solvents, heat, or other inhospitable activities can greatly reduce bioburden of a process. The contribution of compression (and associated shear), for example, should be evaluated for a potential reduction in risk of excessive microbial contamination (Blair 1991). The contribution of the finished product water activity should also contribute to this analysis (USP 2007).
Of particular importance in this evaluation for the potential for microbial contamination of the process are cleaning steps, equipment hold times, HVAC, control level of environments for critical tasks, open-system vs closed-system operations, and bioburden monitoring (among others specific to your process). As an example of the importance of the bioburden control point issue, there is a strong regulatory expectation in Europe that products sterilized by filtration should have a pre-filtration bioburden of not more than 10 CFU/100 mL immediately before the sterilizing filter.
Finally the Contamination Control Plan should cite the need clear SOPs on all aspects of manufacturing, monitoring and control. These SOPs are critical for training, documentation and batch release.
Minimization of Batch Residual Cross-over Contamination
The contamination control plan should also address the potential for a batch to be contaminated by material from the previous batch manufactured using that equipment. Obviously, the contamination control plan should describe the methods by which this likelihood is minimized.
The concern over batch residual cross-over is most relevant when there is more than one product manufactured at a site. This concern has little to do with the sterility of the finished product, and is relevant to sterile and non-sterile manufacture alike.
Minimization of Cleaning Material Residual Contamination
Validation of cleaning procedures is essential to demonstrate not only that the cleaning procedure effectively cleans and sanitizes the manufacturing equipment, but also that residual cleaning material is removed to prevent contamination of the next batch manufactured.
Conclusions
The Contamination Control Plan is an important document designed to formalize the rationale, methods and validation of contamination control procedures in a manufacturing facility. This plan is a valuable tool for pharmaceutical, medical device and personal product manufactures and should be written to address all phases of the facilities life cycle. The Contamination Control Plan should specifically address:
Minimizing the bioburden throughout the manufacturing processes
Minimizing the level of batch residual cross-over contamination
Minimizing the level of cleaning material residual contamination
The microbiologist, as SME, has a critical role to play in the first of these three primary goals, and this essay has therefore been directed at that first topic. Minimization of bioburden in the manufacturing process occurs through (but is not limited to):
Minimizing bioburden in the process
Control incoming bioburden
Appropriate Gowning
Controlled Environments
Well-defined Standard Operating Procedures; and
Well-defined and understood manufacturing processes.
The development of a contamination control program is critical to the effort to get a new facility qualified, and to maintain the facility in a state of control once qualified. The design and successful execution of a contamination control program requires a plan. The creation of a specific document allows the company philosophy, goals, and expectations to be formalized and agreed to by all parties. It also provides the goals and metrics by which the state of control for the facility can be measured in the annual review. The business reasons for this are obvious in terms of reduced regulatory risk and reduction of rejected/recalled batches (Lowry 2001).
This plan is important no matter what type of facility is being developed. Although it is most frequently used in the Quality plan for commissioning an aseptic facility, this is also important and should be used for commissioning and controlling facilities using terminal sterilization, and for non-sterile manufacturing facilities.
Why be concerned with contamination control in a nonsterile manufacturing facility? In many ways contamination control is more of a concern in a non-sterile facility than in sterile product production facilities. The sterile production facility knows there is a problem with contamination and cross-contamination of batches, the non-sterile facility has a great temptation to belief they are not touched by these issues. This can lead to an extremely cavalier attitude about contamination control by the operators and management. The non-sterile manufacturer is responsible for all aspects of his product, including any objectionable organisms present (Sutton, 2006) as described in a recent newsletter (PMF Newsletter v12 n7).
The API manufacturer is also concerned with contamination control. The FDA has explicit instruction on this score (FDA 1998) out of CBER. The EMEA guidance on API manufacture also includes guidance on control of bioburden and cross-contamination of batches (EMEA 2000).
This essay will not be able to provide more than an overview of issues in the space available this month. However, it is hoped that the need for an adequate contamination control plan for a facility will be made clear, and the beginnings of the content of such a plan explained. The interested reader is referred to the articles listed in the “References” and the “Further Readings” sections.
Scope
The Contamination Control Plan should be developed as part of the facility commissioning effort. As such, there will be four distinct phases of the facility operations that will need to be addressed:
Commissioning and initial start-up
Ongoing Operations
Shut-down for regular maintenance
Start-up after scheduled shut-down.
These phases will not have the same level of contamination control. In fact, the third and fourth phases may well have different levels of control to be addressed. A good plan will discuss the concerns specific to each of these phases.
This program, and the protocol governing the program, are essential documents useful in documenting the rationale and methods used to accomplish three tasks:
Minimizing the bioburden throughout the manufacturing processes
Minimizing the level of batch residual cross-over contamination
Minimizing the level of cleaning material residual contamination
As the SME (Subject Matter Expert) in microbiology, we will be most heavily involved in the first of these three tasks, minimizing bioburden. However, all three will be discussed (at least briefly) in this essay for context.
Minimizing Bioburden
Validated methods
All measures of bioburden in a facility will be indirect. We cannot count bacterial cells on a surface or in the air. We must transfer the microorganisms to an agar plate (or some other mechanism) and count colony forming units. If we make the assumption that the transfer of microorganisms from the air or from a surface to agar is consistent, then we can use these numbers to estimate trends over time. This assumes that the nutrient agar is capable of growing the microorganisms to visible colonies. As residual disinfectant on a surface may impede the growth of microorganisms, neutralizers are frequently incorporated into the growth media (Dey-Engley agar, MCTA, etc.). All sampling methods must be validated for the conditions of use.
The facility should be disinfected regularly using validated sanitizers and sporicides. The contamination control plan should describe the methods for testing and rationale for acceptance of materials to be used in the ongoing program of disinfection. The plan should ideally describe the in vitro or laboratory tests to evaluate the sanitizers, including the identification of the most resistant microorganisms found in the facility as well as the most difficult-to-disinfect materials in the facility. This is also where the method for on-going evaluation of the sanitizers based on environmental monitoring data will be recorded. The choice of disinfection regimens should be reevaluated annually, and the contamination control plan should describe how this evaluation will occur.
Know the enemy
A successful contamination control program is geared to providing the most useful information on the microorganisms present while at the same time showing some fiscal responsibility. The FDA aseptic processing guidance document recommends genetic identification of all organisms isolated from the manufacturing environment on a regular basis. (FDA, 2004) This is a laudable goal, but few of us have anything near the required budget to accomplish this task, and in all honesty it is reasonable to wonder if it is really necessary. The numbers of CFU from validated sites (viable air and surface, non-viable) is sufficient to provide a measure of the state of control of the facility. However, periodic cataloging of the resident microflora will provide you with a good check on the continued effectiveness of the disinfectants in use. Shifts of bioburden to spore forming microorganisms will be strong evidence of the need for use of a sporicidal agent. Occasionally, this effort will also pick up shifts among non-spore-forming organisms – this is not due to “resistance” but rather ecological shifts towards species more naturally resistant to the disinfectant in use.
Control incoming bioburden
The first step in any control program is to control contamination at the very beginning of the process. This includes raw materials (excipients, API, water, etc) and the primary containers. All materials should be tested for incoming bioburden against documented acceptance criteria. Part of the incoming bioburden will also be any water used as an excipient to the process. A good guide for the water bioburden is the EMEA guidance on the subject (EMEA 2002).
Appropriate gowning
The gowning methods and materials are of critical importance to minimization of contamination. Although most attention is placed on aseptic gowning procedures, the appropriate use of gowning precautions will be a great boon to most non-sterile manufacturing facilities as well. All personnel should be well-trained in appropriate gowning practice and behavior. The contamination control plan should describe the rationale for the level of gowning chosen, the frequency of gown cleaning, behavior and the acceptable gown materials for the type of manufacturing process.
Training
Operator training is critical to contamination control. No supervisor can be present at all locations at all times. Each operator must be aware of his or her role in contamination control and how to minimize the risk to batch integrity. The PDA has published a technical report that speaks to some of these training requirements from the microbiological perspective (PDA 2001).
Controlled Environments
Control and monitoring of the environment is another critical element of the contamination control plan. Large portions of this can be addressed by the corporate Environmental Monitoring Master Plan (which provides rationale and consistency for a single EM philosophy across the different facilities of the corporation) or the site Environmental Master Plan (which provides consistency and detailed instruction for the various manufacturing buildings at a given site). However, the Contamination Control Plan should cite the relevant documents and their role in contamination control. Those interested in more on environmental monitoring should refer to the PDA’s treatment of the subject for a good overview (PDA 2001).
The appropriate Environmental Monitoring (EM) plan for non-sterile manufactures and for API manufacturers is not well-defined from a regulatory sense. There are no strong recommendations such as those seen for the environmental monitoring of aseptic facilities; however the absence of regulatory guidance is not the same thing as the absence of need for the activity. EM is useful for determining the state of control of the facility (not so much, perhaps an indicator of the finished product quality) and so is an important part of the monitoring program for all manufacturers.
Well-defined and Understood Manufacturing Processes
The manufacturing process should be evaluated for its potential to limit or eliminate bioburden. The two common methods for performing this is either a HACCP-type (Jahnke and Kuhn 2003) or a FMEA approach. The use of organic solvents, heat, or other inhospitable activities can greatly reduce bioburden of a process. The contribution of compression (and associated shear), for example, should be evaluated for a potential reduction in risk of excessive microbial contamination (Blair 1991). The contribution of the finished product water activity should also contribute to this analysis (USP 2007).
Of particular importance in this evaluation for the potential for microbial contamination of the process are cleaning steps, equipment hold times, HVAC, control level of environments for critical tasks, open-system vs closed-system operations, and bioburden monitoring (among others specific to your process). As an example of the importance of the bioburden control point issue, there is a strong regulatory expectation in Europe that products sterilized by filtration should have a pre-filtration bioburden of not more than 10 CFU/100 mL immediately before the sterilizing filter.
Finally the Contamination Control Plan should cite the need clear SOPs on all aspects of manufacturing, monitoring and control. These SOPs are critical for training, documentation and batch release.
Minimization of Batch Residual Cross-over Contamination
The contamination control plan should also address the potential for a batch to be contaminated by material from the previous batch manufactured using that equipment. Obviously, the contamination control plan should describe the methods by which this likelihood is minimized.
The concern over batch residual cross-over is most relevant when there is more than one product manufactured at a site. This concern has little to do with the sterility of the finished product, and is relevant to sterile and non-sterile manufacture alike.
Minimization of Cleaning Material Residual Contamination
Validation of cleaning procedures is essential to demonstrate not only that the cleaning procedure effectively cleans and sanitizes the manufacturing equipment, but also that residual cleaning material is removed to prevent contamination of the next batch manufactured.
Conclusions
The Contamination Control Plan is an important document designed to formalize the rationale, methods and validation of contamination control procedures in a manufacturing facility. This plan is a valuable tool for pharmaceutical, medical device and personal product manufactures and should be written to address all phases of the facilities life cycle. The Contamination Control Plan should specifically address:
Minimizing the bioburden throughout the manufacturing processes
Minimizing the level of batch residual cross-over contamination
Minimizing the level of cleaning material residual contamination
The microbiologist, as SME, has a critical role to play in the first of these three primary goals, and this essay has therefore been directed at that first topic. Minimization of bioburden in the manufacturing process occurs through (but is not limited to):
Minimizing bioburden in the process
Control incoming bioburden
Appropriate Gowning
Controlled Environments
Well-defined Standard Operating Procedures; and
Well-defined and understood manufacturing processes.
Microbial Limits Tests: The Difference Between “Absence of Objectionable Microorganisms” and “Absence of Specified Microorganisms”
We have to note from the outset that USP and FDA frequently are interested in the same thing. From the vantage point of USP, there is a need to have a test for sterility, for antimicrobial efficacy, for Antibiotic/ Vitamin Potency, for Bacterial Endotoxin, for Microbial Limits etc. The need for these tests is not driven by any concern over “Good Manufacturing Process” (GMP). It is governed by the USP monographs found in the National Formulary (NF). If there is a monograph that requires a test for antimicrobial efficacy, then chapter <51> Antimicrobial Effectiveness Test” is the referee test used to demonstrate that characteristic.
FDA has similar, but separate concerns. Where the requirements are identical, the referee chapters in USP (those numbered under <1000>) are enforced. However, there are situations where the FDA’s concerns are not covered by a USP referee test method. One such situation is with the CFR requirement that medicines be “free of objectionable microorganisms.” 21CFR 211.113 under the section “Control of microbiological contamination. (a)” states “Appropriate written procedures, designed to prevent objectionable microorganisms on drug products not required to be sterile, shall be established and followed.” This is reinforced by 21 CFR 211.165 which states “Testing and release for distribution... (b) There shall be appropriate laboratory testing, as necessary, of each batch of drug product required to be free of objectionable microorganisms.”
So, here we have a problem. The USP monograph for a product (as provided in the current National Formulary) may require “Absence of Pseudomonas aeruginosa.” There is a test in the Microbial Limits chapter to demonstrate the absence of Pseudomonas aeruginosa. However, although this test may be required to demonstrate compliance with the monograph requires as laid out in NF it does not meet the FDA concern that any organism in the final product be acceptable to the product and the target population (i.e. are not “objectionable”).
The FDA Concern
FDA will enforce the GMP requirement that if your product approval to market submission contained a statement that you would test the finished product by the Microbial Limits Tests that in fact you must do that. This is purely a GMP concern. However, the Agency has been absolutely clear on the concern over objectionable microorganisms in the product, and that fact that testing to the USP chapter might be necessary, but it is not sufficient to demonstrate microbial quality. In fact, in the 1993 instructional guide for inspections of QC Microbiology Labs (1) the FDA states:
“For a variety of reasons, we have seen a number of problems associated with the microbiological contamination of topical drug products, nasal solutions and inhalation products. The USP Microbiological Attributes Chapter <1111> provides little specific guidance other than "The significance of microorganisms in nonsterile pharmaceutical products should be evaluated in terms of the use of the product, the nature of the product, and the potential hazard to the user." The USP recommends that certain categories be routinely tested for total counts and specified indicator microbial contaminants. For example natural plant, animal and some mineral products for Salmonella, oral liquids for E. Coli [sic], topicals for P. aeruginosa and S. Aureus [sic], and articles intended for rectal, urethral, or vaginal administration for yeasts and molds. A number of specific monographs also include definitive microbial limits.
As a general guide for acceptable levels and types of microbiological contamination in products, Dr. Dunnigan of the Bureau of Medicine of the FDA commented on the health hazard. In 1970, he said that topical preparations contaminated with gram negative organisms are a probable moderate to serious health hazard. Through the literature and through our investigations, it has been shown that a variety of infections have been traced to the gram negative contamination of topical products. The classical example being the Pseudomonas cepacia contamination of Povidone Iodine products reported by a hospital in Massachusetts several years ago.
Therefore, each company is expected to develop microbial specifications for their nonsterile products. Likewise, the USP Microbial Limits Chapter <61> provides methodology for selected indicator organisms, but not all objectionable organisms. For example, it is widely recognized that Pseudomonas cepacia is objectionable if found in a topical product or nasal solution in high numbers; yet, there are no test methods provided in the USP that will enable the identification of the presence of this microorganism.
A relevant example of this problem is the recall of Metaproterenol Sulfate Inhalation Solution. The USP XXII monograph requires no microbial testing for this product. The agency classified this as a Class I recall because the product was contaminated with Pseudomonas gladioli/cepacia. The health hazard evaluation commented that the risk of pulmonary infection is especially serious and potentially life-threatening to patients with chronic obstructive airway disease, cystic fibrosis, and immuno- compromised patients. Additionally, these organisms would not have been identified by testing procedures delineated in the general Microbial Limits section of the Compendia. . . .
Microbiological testing may include an identification of colonies found during the Total Aerobic Plate Count test. Again, the identification should not merely be limited to the USP indicator organisms.
The importance of identifying all isolates from either or both Total Plate Count testing and enrichment testing will depend upon the product and its intended use. Obviously, if an oral solid dosage form such as a tablet is tested, it may be acceptable to identify isolates when testing shows high levels. However, for other products such as topicals, inhalants or nasal solutions where there is a major concern for microbiological contamination, isolates from plate counts, as well as enrichment testing, should be identified.”
Why is this a concern? To understand this we have to go back to the 1970’s. USP had a test for the “Bacteriological Examination of Gelatin” as early as 1942 (2). However, most non-sterile medications in the US were not required to assay for microbiological quality attributes until the introduction of the Microbial Limits Tests in 1970 (3). In the late 1960’s several outbreaks of disease were traced back to pathogencontaminated medications, and this prompted increased attention to the microbial content of non-sterile drugs (4). Later in the 1980’s there was a series of articles appearing in the literature describing contamination by P. cepacia (currently Burkholderia cepacia) (5, 6) and its survival in disinfectants(7 – 11). This lead to the addition of requirements in the 21 CFR to ensure that there are not objectionable organisms in product released to market (see above). Add to this the knowledge that the USP “Absence of Pseudomonas aeruginosa” assay will not identify presence of B. cepacia (as discussed).
The USP Concern
The USP is on record as early as 1982 verifying that the demonstration of “absence of objectionable microorganisms” is not the intent of the chapter. In a one page Stimuli to the Revision Process the microbiology committee of the time states:
“The tests described in the Microbial Limits Tests <61> were not designed to be all-inclusive, i.e., to detect all potential pathogens. To accomplish this, an extensive text on laboratory detection of microorganisms would be required. The procedures in USP were designed to detect the presence of specific “index” or “indicator” organisms. Nevertheless, the present chapter does not preclude the detection of Ps. Cepacia – the organism requires subsequent differentiation. The chapter does not provide specific methods for this, nor does it provide procedures for detecting thousands of other potentially pathogenic organisms. Individual monographs include requirements for limits on total aerobic counts and/or absence of one or more of the four selected “indicator” organisms. The chapter on Microbial Limits Tests provides methods to assure that one may test for those microbial requirements in the individual monographs...
In conclusion, the Microbial Attributes and Microbial Limit Tests chapters accomplish their intent. If a manufacturer needs particular tests for any specific organisms that are potential problems in a process or a final product, the quality control microbiologist can provide specific detection procedures. Many such procedures are published in several laboratory texts on microbiology.”
Conclusions
On the question of the microbial quality of non-sterile pharmaceuticals, the USP and the FDA are in agreement – the product must be safe for use. The NF monograph requirements for absence of specific organisms is a minimal requirement, and should not be taken as proof that the product is suitable for sale from a microbiological perspective.
The manufacturer is responsible for the quality and safety of the product marketed, and it is the clear expectation of FDA (as described in CFR) that this will include a determination of the microbial safety – i.e. the “absence of objectionable microorganisms” from the product. These positions have been publicly stated for decades and should not come as a surprise to anyone. The harmonized microbial limits tests only address the “absence of specified microorganisms” and leave the determination of the “absence of objectionable microorganisms” in the capable hands of each company’s appropriately educated and well-trained microbiology group.
FDA has similar, but separate concerns. Where the requirements are identical, the referee chapters in USP (those numbered under <1000>) are enforced. However, there are situations where the FDA’s concerns are not covered by a USP referee test method. One such situation is with the CFR requirement that medicines be “free of objectionable microorganisms.” 21CFR 211.113 under the section “Control of microbiological contamination. (a)” states “Appropriate written procedures, designed to prevent objectionable microorganisms on drug products not required to be sterile, shall be established and followed.” This is reinforced by 21 CFR 211.165 which states “Testing and release for distribution... (b) There shall be appropriate laboratory testing, as necessary, of each batch of drug product required to be free of objectionable microorganisms.”
So, here we have a problem. The USP monograph for a product (as provided in the current National Formulary) may require “Absence of Pseudomonas aeruginosa.” There is a test in the Microbial Limits chapter to demonstrate the absence of Pseudomonas aeruginosa. However, although this test may be required to demonstrate compliance with the monograph requires as laid out in NF it does not meet the FDA concern that any organism in the final product be acceptable to the product and the target population (i.e. are not “objectionable”).
The FDA Concern
FDA will enforce the GMP requirement that if your product approval to market submission contained a statement that you would test the finished product by the Microbial Limits Tests that in fact you must do that. This is purely a GMP concern. However, the Agency has been absolutely clear on the concern over objectionable microorganisms in the product, and that fact that testing to the USP chapter might be necessary, but it is not sufficient to demonstrate microbial quality. In fact, in the 1993 instructional guide for inspections of QC Microbiology Labs (1) the FDA states:
“For a variety of reasons, we have seen a number of problems associated with the microbiological contamination of topical drug products, nasal solutions and inhalation products. The USP Microbiological Attributes Chapter <1111> provides little specific guidance other than "The significance of microorganisms in nonsterile pharmaceutical products should be evaluated in terms of the use of the product, the nature of the product, and the potential hazard to the user." The USP recommends that certain categories be routinely tested for total counts and specified indicator microbial contaminants. For example natural plant, animal and some mineral products for Salmonella, oral liquids for E. Coli [sic], topicals for P. aeruginosa and S. Aureus [sic], and articles intended for rectal, urethral, or vaginal administration for yeasts and molds. A number of specific monographs also include definitive microbial limits.
As a general guide for acceptable levels and types of microbiological contamination in products, Dr. Dunnigan of the Bureau of Medicine of the FDA commented on the health hazard. In 1970, he said that topical preparations contaminated with gram negative organisms are a probable moderate to serious health hazard. Through the literature and through our investigations, it has been shown that a variety of infections have been traced to the gram negative contamination of topical products. The classical example being the Pseudomonas cepacia contamination of Povidone Iodine products reported by a hospital in Massachusetts several years ago.
Therefore, each company is expected to develop microbial specifications for their nonsterile products. Likewise, the USP Microbial Limits Chapter <61> provides methodology for selected indicator organisms, but not all objectionable organisms. For example, it is widely recognized that Pseudomonas cepacia is objectionable if found in a topical product or nasal solution in high numbers; yet, there are no test methods provided in the USP that will enable the identification of the presence of this microorganism.
A relevant example of this problem is the recall of Metaproterenol Sulfate Inhalation Solution. The USP XXII monograph requires no microbial testing for this product. The agency classified this as a Class I recall because the product was contaminated with Pseudomonas gladioli/cepacia. The health hazard evaluation commented that the risk of pulmonary infection is especially serious and potentially life-threatening to patients with chronic obstructive airway disease, cystic fibrosis, and immuno- compromised patients. Additionally, these organisms would not have been identified by testing procedures delineated in the general Microbial Limits section of the Compendia. . . .
Microbiological testing may include an identification of colonies found during the Total Aerobic Plate Count test. Again, the identification should not merely be limited to the USP indicator organisms.
The importance of identifying all isolates from either or both Total Plate Count testing and enrichment testing will depend upon the product and its intended use. Obviously, if an oral solid dosage form such as a tablet is tested, it may be acceptable to identify isolates when testing shows high levels. However, for other products such as topicals, inhalants or nasal solutions where there is a major concern for microbiological contamination, isolates from plate counts, as well as enrichment testing, should be identified.”
Why is this a concern? To understand this we have to go back to the 1970’s. USP had a test for the “Bacteriological Examination of Gelatin” as early as 1942 (2). However, most non-sterile medications in the US were not required to assay for microbiological quality attributes until the introduction of the Microbial Limits Tests in 1970 (3). In the late 1960’s several outbreaks of disease were traced back to pathogencontaminated medications, and this prompted increased attention to the microbial content of non-sterile drugs (4). Later in the 1980’s there was a series of articles appearing in the literature describing contamination by P. cepacia (currently Burkholderia cepacia) (5, 6) and its survival in disinfectants(7 – 11). This lead to the addition of requirements in the 21 CFR to ensure that there are not objectionable organisms in product released to market (see above). Add to this the knowledge that the USP “Absence of Pseudomonas aeruginosa” assay will not identify presence of B. cepacia (as discussed).
The USP Concern
The USP is on record as early as 1982 verifying that the demonstration of “absence of objectionable microorganisms” is not the intent of the chapter. In a one page Stimuli to the Revision Process the microbiology committee of the time states:
“The tests described in the Microbial Limits Tests <61> were not designed to be all-inclusive, i.e., to detect all potential pathogens. To accomplish this, an extensive text on laboratory detection of microorganisms would be required. The procedures in USP were designed to detect the presence of specific “index” or “indicator” organisms. Nevertheless, the present chapter does not preclude the detection of Ps. Cepacia – the organism requires subsequent differentiation. The chapter does not provide specific methods for this, nor does it provide procedures for detecting thousands of other potentially pathogenic organisms. Individual monographs include requirements for limits on total aerobic counts and/or absence of one or more of the four selected “indicator” organisms. The chapter on Microbial Limits Tests provides methods to assure that one may test for those microbial requirements in the individual monographs...
In conclusion, the Microbial Attributes and Microbial Limit Tests chapters accomplish their intent. If a manufacturer needs particular tests for any specific organisms that are potential problems in a process or a final product, the quality control microbiologist can provide specific detection procedures. Many such procedures are published in several laboratory texts on microbiology.”
Conclusions
On the question of the microbial quality of non-sterile pharmaceuticals, the USP and the FDA are in agreement – the product must be safe for use. The NF monograph requirements for absence of specific organisms is a minimal requirement, and should not be taken as proof that the product is suitable for sale from a microbiological perspective.
The manufacturer is responsible for the quality and safety of the product marketed, and it is the clear expectation of FDA (as described in CFR) that this will include a determination of the microbial safety – i.e. the “absence of objectionable microorganisms” from the product. These positions have been publicly stated for decades and should not come as a surprise to anyone. The harmonized microbial limits tests only address the “absence of specified microorganisms” and leave the determination of the “absence of objectionable microorganisms” in the capable hands of each company’s appropriately educated and well-trained microbiology group.
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