What Is MIC?

The MIC is the lowest concentration of antimicrobial agent which inhibits the growth of the microorganism.

A current definition of the Minimum Inhibitory Concentration, MIC, is "the lowest concentration which resulted in maintenance or reduction of inoculum viability".

Antibiotic resistance is the ability of a microorganism to withstand the effects of an antibiotic. Antibiotic resistance develops through mutation or plasmid exchange between bacteria of the same species. If a bacterium carries several resistance genes, it is called multiresistant or, informally, a superbug.

Antibiotic resistance is a consequence of evolution via natural selection. The antibiotic action is an environmental pressure; those bacteria which have a mutation allowing them to survive will live on to reproduce. They will then pass this trait to their offspring, which will be a fully resistant generation.

Several studies have demonstrated that patterns of antibiotic usage greatly affect the number of resistant organisms which develop. Overuse of broad-spectrum antibiotics, such as second and third generation cephalosporins, greatly hastens the development of methicillin resistance, even in organisms that have never been exposed to the selective pressure of methicillin per se. Other factors contributing towards resistance include incorrect diagnosis, unnecessary prescriptions, improper use of antibiotics by patients, and the use of antibiotics as livestock food additives for growth promotion.

The determination of the MIC involves a semi-quantitative test procedure which gives an approximation to the least concentration of an antimicrobial needed to prevent microbial growth. In the recent past, the method used tubes of growth broth containing a test level of preservative, into which an inoculum of microbes was added. The end result of the test was the minimum concentration of antimicrobial which gave a clear solution, i.e., no visual growth.

Currently, the tubes have been replaced by a semi-automated microtitre method. Where the turbidity of the test compound interferes with the test, indicators can be used for the determination of the end-point.

A broad-spectrum antibiotic is so called due to its activity against a wide range of infectious agents. A good example is amoxicillin.

Broad-spectrum antibiotics are used in roughly two medical situations:

Where the infectious agent will not become known in the course of the disease, e.g. in a child moderately ill with bronchitis. In this case no cultures are being taken. When the patient is ill enough to warrant antibiotic treatment, even though culture results are not yet known. This occurs, for example, in meningitis, where the patient is so ill that he/she would die within hours if broad-spectrum antibiotics are not initiated. Generally, the spectrum is "narrowed down" when the causative agent of an infection becomes known, and the broad-spectrum agent is replaced by a narrower-spectrum antibiotic. This is supposed to limit the development of antibiotic resistance, although evidence for this practice is unclear.

The minimum inhibitory concentration is the minimum concentration of the antibacterial agent in a given culture medium below which bacterial growth is not inhibited.

The cephalosporins, are a class of ß-lactam antibiotics. Together with cephamycins they belong to a sub-group called cephems.

Cephalosporin was first isolated from cultures of Cephalosporium acremonium from a sewer in Sardinia in 1948 by an italian scientist Giuseppe Brotzu. He noticed that these cultures produced a substance that was effective against salmonella typhi, the cause of typhoid. In 1960s, Eli Lilly launched the first cephalosporins on the market.

Cephalosporins work the same way as penicillins, they interfere with the peptidoglycan synthesis of the bacterial wall by inhibiting the final transpeptidation needed for the cross-links. This effect is bactericidal.

Staphylococcus aureus (colloquially known as "Staph aureus") is one of the major resistant pathogens. Found on the mucous membranes and the skin of around a third of the population, it is extremely adaptable to antibiotic pressure. It was the first bacterium in which penicillin resistance was found -- in 1947, just four years after the drug started being mass-produced. Methicillin was then the antibiotic of choice. MRSA (methicillin-resistant Staphylococcus aureus) was first detected in Britain in 1961 and is now "quite common" in hospitals. MRSA was responsible for 37% of fatal cases of blood poisoning in the UK in 1999, up from 4% in 1991. Half of all S. aureus infections in the US are resistant to penicillin, methicillin, tetracycline and erythromycin.

This left vancomycin as the only effective agent available at the time. A new class of antibiotics, oxazolidinones, became available in the 1990s, and the first commercially available oxazolidinone, linezolid, is comparable to vancomycin in effectiveness against MRSA. However, VRSA (Vancomycin-resistant Staphylococcus aureus) was first identified in Japan in 1997 and has since been found in hospitals in England, France and the US.

For an antimicrobial agent to be effective, it must reach the site of infection in sufficient concentration and duration to inhibit pathogen growth. Since the introduction of the short-half-life antibiotic aqueous penicillin G 60 years ago, the traditional approach to predicting in vivo efficacy of antimicrobial agents has been to compare the peak antimicrobial serum concentration with the minimum concentration of the antibiotic that inhibits growth of the pathogen. This minimum inhibitory concentration (MIC) usually is measured in a test tube or on an agar plate.

VRSA is also termed GISA (glycopeptide intermediate Staphylococcus aureus) or VISA (vancomycin intermediate Staphylococcus aureus), indicating resistance to all glycopeptide antibiotics.

Enterococcus faecium is another superbug found in hospitals: penicillin resistance was seen in 1983, vancomycin resistance (VRE) in 1987 and linezolid resistance (LRE) in the late 1990s.

The sensitivity of bacterial strains to antibacterial agents is generally defined by the minimum inhibitory concentration (MIC) of a particular agent in vitro. Against the species under investigation. This method is unsuitable, however. for species which develop intracellularly such as mycobacteria.

Penicillin-resistant pneumonia (or pneumococcus, caused by Streptococcus pneumoniae) was first detected in 1967, as was penicillin-resistant gonorrhea. Resistance to penicillin substitutes is also known beyond S. aureus. By 1993 Escherichia coli was resistant to five fluoroquinolone variants. Mycobacterium tuberculosis is commonly resistant to isoniazid and rifampin and sometimes universally resistant to the common treatments. Other pathogens showing some resistance include Salmonella, Campylobacter, and Streptococci.

The MIC of the infecting pathogen and the drug's half-life have been used to determine an antibiotic's dose and interval. If the offending pathogen's MIC was below a predetermined breakpoint, based on the peak serum level for that antibiotic, the organism was considered susceptible and therapy would be initiated. The MIC still provides a good prediction of the potency of an antibiotic against a given pathogen, but it does not provide any information on the time course of the activity or the activity at the site of infection.

Staphylococcus aureus (also known as golden staph) is a bacterium, frequently living on the skin or in the nose of a healthy person, that can cause illnesses ranging from minor skin infections (such as pimples, boils, and cellulitis) and abscesses, to life-threatening diseases such as pneumonia, meningitis, endocarditis and septicemia.

Each year some 500,000 patients in American hospitals contract a staphylococcal infection. By changing its chemical makeup slightly to evade attack, S. aureus has become resistant to many commonly used antibiotics (see discussion about MRSA). In 1997, physicians were alarmed to encounter staph strains that resist even vancomycin, which used to work when all else failed. Problems with S. aureus in hospitals are not a recent occurance, as penicillin resistant forms have existed since the 1950's.

Staphylococcus aureus appears as a gram-positive coccus, in grape-like clusters when viewed through a microscope. More characteristic is its appearance when grown out on agar plates. It appears as large, round golden-yellow (which is where the name aureus comes from) colonies, with beta-haemolysis of blood agar.

Staph infections can be spread through contact with pus from an infected wound, skin to skin contact with an infected person, and contact with objects such as towels, sheets, clothing, or athletic equipment used by an infected person.

In the hospital laboratory, Staphylococcus aureus is differentiated from most other staphylococci by the coagulase test. Staphylococcus aureus is coagulase-positive.

Please note that Golden Staph is known as a 'Superbug' due to its high immunity and resistance against standard antibiotic treaments.

When a bacteria population can be exposed to an antibiotic in-vitro in the same way as it is in vivo, the in-vitro experiments quantify the efficacy of the antibiotic. When the antibiotic has strong side effects, one has to optimize between those effects and the risk of losing control over the bacteria population. In such critical cases an in-vitro model with only one parameter, the Minimum Inhibitory Concentration, may not be able to describe the development of an in-vitro bacteria population accurately enough.

Antibiotics can also be classified by the organisms against which they are effective, and by the type of infection in which they are useful, which depends on the sensitivities of the organisms that most commonly cause the infection and the concentration of antibiotic obtainable in the affected tissue.

Side effects. Side effects range from slight headache to a major allergic reaction. One of the more common side effects is diarrhea, which results from the antibiotic disrupting the balance of intestinal flora, the "good bacteria" that dwell inside the human digestive system. Other side effects can result from interaction between the antibiotic and other drugs, such as elevated risk of tendon damage from administration of a quinolone antibiotic with a systemic corticosteroid.

Antibiotic misuse. Common forms of antibiotic misuse include taking an inappropriate antibiotic, in particular the use of antibacterials for viral infections like the common cold, and failure to take the entire prescribed course of the antibiotic, usually because the patient feels better before the infecting organism is completely eradicated. In addition to treatment failure, these practices can result in antibiotic resistance. In the United States, a vast quantity of antibiotics is routinely included as low doses in the diet of healthy farm animals, as this practice has been proved to make animals grow faster. Opponents of this practice, however, point out the likelihood that it also leads to antibiotic resistance, frequently in bacteria that are known to also infect humans, although there has been little or no evidence as yet of such transfer of antibiotic resistance actually occurring.

Antibiotic resistance. One side effect of misusing antibiotics is the development of antibiotic resistance by the infecting organisms, similar to the development of pesticide resistance in insects. Evolutionary theory of genetic selection requires that as close as possible to 100% of the infecting organisms be killed off to avoid selection of resistance; if a small subset of the population survives the treatment and is allowed to multiply, the average susceptibility of this new population to the compound will be much less than that of the original population, since they have descended from those few organisms which survived the original treatment. This survival often results from an inheritable resistance to the compound, which was infrequent in the original population but is now much more frequent in the descendants thus selected entirely from those originally infrequent resistant organisms.

Antibiotic resistance has become a serious problem in both the developed and underdeveloped nations. By 1984 half the people with active tuberculosis in the United States had a strain that resisted at least one antibiotic. In certain settings, such as hospitals and some child-care locations, the rate of antibiotic resistance is so high that the normal, low cost antibiotics are virtually useless for treatment of frequently seen infections. This leads to more frequent use of newer and more expensive compounds, which in turn leads inexorably to the rise of resistance to those drugs, and a never-ending ever-spiraling race to discover new and different antibiotics ensues, just to keep us from losing ground in the battle against infection. The fear is that we will eventually fail to keep up in this race, and the time when people did not fear life-threatening bacterial infections will be just a memory of a golden era.

Another example of selection is Staphylococcus aureus, which could be treated successfully with penicillin in the 1940s and 1950s. At present, nearly all strains are resistant to penicillin, and many are resistent to nafcillin, leaving only a narrow selection of drugs such as vancomycin useful for treatment. The situation is worsened by the fact that genes coding for antibiotic resistance can be transferred between bacteria, making it possible for bacteria never exposed to an antibiotic to acquire resistance from those which have. The problem of antibiotic resistance is worsened when antibiotics are used to treat disorders in which they have no efficacy, such as the common cold or other viral complaints, and when they are used widely as prophylaxis rather than treatment (as in, for example, animal feeds), because this exposes more bacteria to selection for resistance.

Beyond antibiotics. Unfortunately, the comparative ease of finding compounds which safely cured bacterial infections proved much harder to duplicate with respect to fungal and viral infections. Antibiotic research led to great strides in our knowledge of basic biochemistry and to the current biological revolution; but in the process it was discovered that the susceptibility of bacteria to many compounds which are safe to humans is based upon significant differences between the cellular and molecular physiology of the bacterial cell and that of the mammalian cell. In contrast, despite the seemingly huge differences between fungi and humans, the basic biochemistries of the fungal cell and the mammalian cell are much more similar; so much so that there are few therapeutic opportunities for compounds to attack a fungal cell which will not harm a human cell. Similarly, we know now that viruses represent an incredibly minimal intracellular parasite, being stripped down to a few genes worth of DNA or RNA and the minimal molecular equipment needed to enter a cell and actually take over the machinery of the cell to produce new viruses. Thus, the great bulk of viral metabolic biochemistry is not merely similar to human biochemistry, it actually is human biochemistry, and the possible targets of antiviral compounds are restricted to the relatively very few components of the actual virus itself.

Staphylocccus Aureus (SA) or Golden Staph is developing resistance even to more extreme antibitotics such as Vancomycin.

MRSA, or methicillin-resistant Staphylococcus aureus, is a bacterium that has developed antibiotic resistance, first to penicillin in 1947, and later to methicillin. Popularly termed a "superbug", it was first discovered in Britain in 1961 and is now widespread. While an MRSA colonisation in an otherwise healthy individual is not usually a serious matter, infection with the organism can be life-threatening to patients with deep wounds, intravenous catheters or other foreign-body instrumentation; or as a secondary infection in patients with compromised immune systems.

Antimicrobial agents that exhibit time-dependent killing demonstrate little difference in rate and extent of killing once the concentration is 2 to 4 times above the MIC; the rate of killing is constant and is not affected by further increases in antimicrobial concentrations. The length of time the antibiotic concentration remains above the MIC affects killing, which is described by the ratio: time greater than MIC (T > MIC). Thus, the goal of therapy with these agents is to maintain the concentration above the MIC for as long as possible during the dosing interval.

Antibiotics that exhibit time-dependent killing include [beta]-lactams, macrolides (with the exception of azithromycin), and clindamycin. (2,8) The dosage adjustments for these agents differ from concentration-dependent agents. Generally, intervals should be maintained to keep the concentration above the MIC for the longest duration of time possible, because little is gained by increasing peak concentrations if T > MIC is inadequate.

Because cystic fibrosis patients are often treated with multiple antibiotics in hospital settings, they are often colonized with MRSA, potentially increasing the rate of life-threatening MRSA pneumonias among them. The risk of cross-colonization has led to increased use of isolation protocols among these patients.

Antibiotic pharmacodynamics is an evolving science that focuses on the relationship between drug concentration and pharmacologic effect, which is an antibiotic-induced bacterial death that also can manifest as an adverse drug reaction. The pharmacologic action of antibiotics usually can be described as concentration dependent or independent, although such classifications are highly reliant on the specific antibiotic and bacterial pathogen being studied. Quantitative pharmacodynamic parameters, such as ratio of the area under the concentration-time curve during a 24-hour dosing period to minimum inhibitory concentration (AUC0-24:MIC), ratio of maximum serum antibiotic concentration to MIC (Cmax:MIC), and duration of time that antibiotic concentrations exceed MIC (T>MIC), have been proposed as likely predictors of clinical and microbiologic success or failure for different pairings of antibiotic and bacteria. Thus far, most pharmacodynamic data reported have focused on fluoroquinolones, but work has been conducted on vancomycin, ß-lactams, macrolides, aminoglycosides, and other antibiotics.

Despite the development of a number of different pharmacodynamic modeling systems, remarkable agreement exists between in vitro, animal, and limited human data. Although still somewhat premature and requiring additional clinical validation, antibiotic pharmacodynamics will likely advance on four fronts: the science should prove to be extremely useful and represent a cost-effective and efficient method to help develop new antibiotics; formulary committees will likely use pharmacodynamic parameters to assist in differentiating antibiotics of the same chemical class in making antibiotic formulary selections; pharmacodynamic principles will likely be used to design optimal antibiotic strategies for patients with severe infections; and limited data to date suggest that the application of pharmacodynamic concepts may limit or prevent the development of antibiotic resistance. The study of antibiotic pharmacodynamics appears to hold great promise and will likely become a routine part of our daily clinical practices.

In the USA there are increasing reports of outbreaks of MRSA colonisation through skin contact in locker rooms and gymnasiums, even among healthy populations, and MRSA causes as many as 20% of Staph aureus infections in populations that use intravenous drugs.

A last-resort antibiotic, Vancomycin, is used to kill MRSA but several new strains of the bacterium (since the first report in 1997) has been found showing resistance to Vancomycin; those new evolutions of the MRSA bateria are dubbed Vancomycin Intermediate-resistant Staphylococcus aureus (VISA).

Tetracycline is an antibiotic produced by the streptomyces bacterium, indicated for use against many bacterial infections. It is sold under the brand names Tetralysal 300®, Panmycin®, Brodspec® and Tetracap®, among others. It is also used to produce several semi-synthetic derivatives, which are known as the Tetracyclines.

History Tetracycline was first discovered by Lloyd Conover in the research departments of Pfizer. The patent for Tetracycline was first issued in 1955 (patent number 2,699,054). Tetracycline sparked the development of many chemically altered antibiotics and in doing so has proved to be one of the most important discoveries made in the field of antiobiotics.

Mechanism and Resistance Tetracycline inhibits cell growth by inhibiting translation. It binds to the 30S ribosomal subunit and prevents the amino-acyl tRNA from binding to the A site of the ribosome. The binding is reversible in nature.

Waste left by chickens raised in industrial chicken houses contains a wealth of bacteria that have antibiotic multi-resistance genes, a new study has found.

Since the development of antibiotics, bacteria have been able to mutate and become resistant to them. In this new study, researchers show how bacteria are able to become resistant to many antibiotics at one time by pasting together genes that are resistant to many antibiotics.

Cells become resistant to tetracyline by at least two mechanisms: efflux and ribosomal protection. In efflux, a resistance gene encodes a membrane protein that actively pumps tetracycline out of the cell. This is the mechanism of action of the tetracycline resistance gene on the artificial plasmid pBR322. In ribosomal protection, a resistance gene encodes a protein which binds to the ribosome and prevents tetracycline from acting on the ribosome.

Contraindications Tetracycline use should be avoided during pregnancy and in the very young (less than 6 years) because it will result in permanent staining of teeth causing an unsightly cosmetic result.

Streptomyces is a genus of Actinobacteria. They are Gram-positive, have a high GC-content and can be found predominantly in soil. Most Streptomycetes produce spores.

Macrolides are a family of antibiotics used to treat a wide range of bacterial infections. Each drug within the family slows the growth of or kills specific bacteria; therefore, healthcare practitioners prescribe macrolides based on the individual's current needs.

The complete genome of one of the species, Streptomyces coelicolor, was published in 2002. It contains the largest number of genes of any bacterium characterised so far. Another unique characteristic is that its chromosome is linear instead of circular.

Streptomycetes are characterised by a complex secondary metabolism. They produce a large number of antibiotics that are in clinical use; the now rarely used Streptomycin takes its name directly from the Streptomyces. They are not known to cause disease themselves.

The minimum inhibitory concentration (MIC) of an antibacterial is defined as the maximum dilution of the product that will still inhibit the growth of a test microorganism. The minimum lethal concentration (MLC) of an antibacterial is defined as the maximum dilution of the product that will kill a test organism. MIC/MLC values can be determined by a number of standard test procedures. The most commonly employed methods are the tube dilution method and agar dilution methods. Serial dilutions are made of the products in bacterial growth media. The test organisms are then added to the dilutions of the products, incubated, and scored for growth. This procedure is a standard assay for antimicrobials. The procedure incorporates the content and intent of the American Society for Microbiology (ASM) recommended methodology.

Erythromycin is a macrolide antibiotic which has an antimicrobial spectrum similar or slightly wider to that of penicillin, and is often used for people who have an allergy to penicillins. For respiratory tract infections, it has better coverage of atypical organisms, including mycoplasma. It is also used to treat outbreaks of chlamydia, syphilis, and gonorrhea.

Erythromycin is produced from a strain of the actinomyces Saccaropolyspora erythraea, formerly known as Streptomyces erythraeus.

Abelardo Aguilar, a Filipino scientist, sent some soil samples to his employer Eli Lilly in 1949. Eli Lilly’s research team, led by J. M. McGuire, managed to isolate erythromycin, and it was subsequently launched in 1952 under the brand name Ilosone (after the Philippine region of Iloilo where it was originally collected from). Erythromycin was formerly also called ilotycin.

Available forms Erythromycin is available in enteric-coated tablets, oral suspensions, ointments, gels and injections.

Mechanism of action Erythromycin prevents bacteria from growing, by interfering with their protein synthesis. Erythromycin binds to the subunit 50S of the bacterial ribosome, and thus inhibits the translocation of peptides.

Pharmacokinetics Erythromycin is easily inactivated by gastric acids, therefore all orally administered formulations are given as either enteric coated or as more stable salts or esters. Erythromycin is very rapidly absorbed, and diffused into most tissues and phagocytes. Due to the high concentration in phagocytes, erythromycin is actively transported to the site of infection, where during active phagocytosis, large concentrations of erythromycin are released.

Metabolism Most of erythromycin is metabolised by demethylation in the liver. Its main route elimination route is in the bile, and a small portion in the urine. Erythromycin's half-life is 1.5 hours.

Side-effects Gastrointestinal intestinal disturbances such as diarrhoea, nausea, abdominal pain and vomiting are fairly common so it tends not to be prescribed as a first-line drug. More serious side-effects, such as reversible deafness are rare. Earlier case reports on sudden death prompted a study on a large cohort that confirmed a link between erythromycin, ventricular tachycardia and sudden cardiac death in patients also taking drugs that prolong the metabolism of erythromycin (like verapamil or diltiazem) by interfering with CYP3A4.

Linezolid is a synthetic systemic antibiotic drug.

It was the first commercially available oxazolidinone antibiotic and is usually reserved for the treatment of serious bacterial infections where older antibiotics have failed due to antibiotic resistance. Conditions such as skin infections or nosocomial pneumonia where methicillin or penicillin resistance is found are indicators for linezolid use. Compared to the older antibiotics it is quite expensive.

The drug works by inhibiting the initiation of bacterial protein synthesis; it is the only antibiotic to work in this manner. That and its synthetic nature raised hopes that bacteria would be unable to develop resistance to it and also remove the chance of cross-resistance. (However, in 1997 Staphylococcus aureus was first identified in Japan as being resistant to linezolid.) Linezolid is effective against gram-positive pathogens, noyably E. faecium, S. aureus, S. agalactiae, S. pneumoniae, and S. pyogenes. It has almost no effect on gram-negative bacteria and is only bacteroistatic against most enterococcus species.

Microbiology is the study of microorganisms A micro-organism or microbe is an organism that is so small that it is invisible to the naked eye. The term is synonymous by usage to single-celled organism, and unicellular organism, even though some unicellular protists are visible to the naked eye, and some colonial species are microscopic. All unicellular organisms are able to reproduce themselves without help of other organisms, as opposed to viruses.

Domain: Eukaryota, Kingdoms, Animalia - Animals Fungi Plantae - Plants Protista

Eukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. They include the animals, plants, and fungi, which are mostly multicellular, as well as various other groups called protists, many of which are unicellular. In contrast, other organisms such as bacteria lack nuclei and other complex cell structures, and are called prokaryotes. The eukaryotes share a common origin, and are often treated formally as a superkingdom, empire, or domain. The name comes from the Greek eus or true and karyon or nut, referring to the nucleus. ..... Click the link for more information. and prokaryotes Prokaryotes are mostly unicellular organisms without a nucleus, in contrast to eukaryotes, organisms that have cell nuclei and may be variously unicellular or multicellular. The difference between prokaryote and eukaryote cell structure is the most important in the living world. Most prokaryotes are bacteria, and the two terms are often treated as synonyms. However, Woese has proposed dividing them into the Bacteria and Archaea (originally Eubacteria and Archaebacteria) on the supposition that these have separate origins. This controversial arrangement is called the three-domain system. ..... Click the link for more information. , fungi

The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. Included are the conspicuous mushrooms, but also many microscopic

The minimum inhibitory concentration is the minimum concentration of the antibacterial agent in a given culture medium below which bacterial growth is not inhibited.

The therapeutic index is thus given by the plasma or tissue toxic concentration divided by the MIC.

Care should be exercised in interpreting the MIC, since it is a culture definition. In tissues the situation may be altered - for example in abcesses the walls may be resistant to the passage of antibiotic.

A common alternate meaning of virus is computer virus. Other meanings, as well as a discussion of pluralization, are at plural of virus.

A virus is a small particle which can infect other biological organisms. Viruses are obligate intracellular parasites meaning that they can only reproduce by invading and taking over other cells as they lack the cellular machinery for self reproduction. The term virus usually refers to those particles which infect eukaryotes (multi-celled organisms and many single-celled organisms), whilst the term bacteriophage or phage is used to describe those infecting prokaryotes (bacteria and bacteria-like organisms). Today, most of the work in microbiology is done using methods from biochemistry Biochemistry is the chemistry of life. Biochemists study the elements, compounds and chemical reactions that are controlled by enzymes and take place in all living organisms.

Biochemistry is focused on the structure and function of cellular components, such as proteins, carbohydrates, lipids, nucleic acids, and other biomolecules. Recently biochemistry has focused more specifically on the chemistry of enzyme-mediated reactions, and on the properties of proteins. and genetics Genetics is the science of genes, heredity, and the variation of organisms. Humans began applying knowledge of genetics in prehistory with the domestication and breeding of plants and animals. In modern research, genetics provides important tools in the investigation of the function of a particular gene, e.g. analysis of genetic interactions. Within organisms, genetic information generally is carried in chromosomes, where it is represented in the chemical structure of particular DNA molecules. ..... Click the link for more information. . It is also related to pathology Pathology is the study of diseases. It is a form of science and a branch of medicine that involves testing samples and diagnosing physical health problems from their evidence. Pathologists are skilled in interpreting test results and physical evidence.

Bacillus anthracis is an appropriate microbe to begin our examination of pathogenesis, because it was the first bacterium shown to cause a disease by Robert Koch in 1877. Koch was able to grow the microbe in pure culture and demonstrate that injection of B. anthracis into a susceptible host caused the disease anthrax. Many of the methodologies developed in demonstrating the causal relationship between growth of B. anthracis on a host and the disease anthrax have been applied to numerous other maladies to discover their causative agents. The terrorist use of anthrax in 2001 has greatly increased public awareness of the causative bacterium and renewed interest in its identification, treatment and prevention.

Antibiotics can be classified as either concentration- or time-dependent bactericidal agents. Concentration-dependent (or time-independent) antibiotics kill at a greater rate and to a greater extent with increasing antibiotic concentrations, whereas time-dependent (or concentration-independent) antibiotics kill bacteria at the same rate and to the same extent once an appropriate antibiotic threshold concentration has been achieved. Increasing the antibiotic concentration beyond this point typically does not augment the antibacterial activity.

In general, aminoglycosides, fluoroquinolones, and metronidazole (against anaerobic bacteria) are considered concentration-dependent killers, whereas vancomycin, clindamycin, macrolides (with the possible exception of azithromycin), and ß-lactams are considered concentration-independent killers. Our understanding is compromised, however, due to limited data involving a relatively small number of bacterial isolates over a confined range of antibiotic concentrations.

Immunology is a broad branch of biomedical science that covers study of all aspects of the immune system in all organisms. It deals with, among other things, the physiological functioning of the immune system in states of both health and disease; malfunctions of the immune system in immunological disorders (autoimmune diseases, hypersensitivities, immune deficiency, allograph rejection); the physical characteristics of organs in the immune system; and in vitro, in vivo and in situ chemical and physiological properties of biological components of the immune system. Immunology has various applications in several disciplines of science, and as such is further categorised accordingly. Epidemiology is the study of the demographics of disease processes, including the study of epidemics and other diseases that are common enough to allow statistical tools to be applied. So, besides contagious diseases, it also focuses on diabetes, coronary heart disease, high blood pressure and the like. Epidemiology is an important auxiliary branch of medicine, helping to find the causes of diseases and ways of prevention (as in the case of AIDS). It can, using statistical methods such as large-scale population studies, support or refute treatment hypotheses. A pathogen is a biological agent that can cause disease to its host. A synonym of pathogen is "infectious agent". The term "pathogen" is most often used for agents that disrupt the normal physiology of a multicellular animal or plant. However, pathogens can infect unicellular organisms from all of the biological kingdoms (see Viruses, below).

OverviewThe human body has many natural defenses against some of the more common pathogens.

Microbiologists have made many fundamental contributions to biology

Biology studies the variety of life (clockwise from top-left) E. coli, tree fern, gazelle, Goliath beetle Biology is the science of life. It is concerned with the characteristics and behaviors of organisms, how species and individuals come into existence, and the interactions they have with each other and with their environment. Biology encompasses a broad spectrum of academic fields that are often viewed as independent disciplines. Together, they study life over a wide range of scales. Cell biology (cellular biology) is an academic discipline which studies the physiological properties of cells, as well as their behaviours, interactions, and environment; this is done both on a microscopic and molecular level. Cell biology researches both single-celled organisms like bacteria and specialized cells in multicellular organisms like humans.

Understanding the composition. Microbes have many traits that make them ideal model organisms A model organism is one that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. This works because evolution reuses fundamental biological principles and conserves metabolic, regulatory, and developmental pathways.

ß-lactams primarily exhibit concentration-independent activity, and the focus has been on T>MIC as a predictive parameter. Results of an experiment published in 1950 found that the major determinant of penicillin activity against pneumococci in an animal model was the amount of time in which drug concentration remained above minimally effective levels.[1] Increased efficacy with larger doses was attributed to an extension in the time the drug remained above the effective concentration, rather than to an increase in absolute concentrations.

There are many model organisms. The first model organism for molecular biology was probably the bacterium Escherichia coli which is common in the human digestive system (and usually beneficial -- the dangerous is a rare strain). This also led to a study of many bacteriophages, particularly phage lambda.

They are small, therefore they do not consume many resources Some have very short generation times (~30 minutes for E. coli Escherichia coli

Escherichia coli. Cells can easily survive in isolation from other cells They can reproduce by mitotic In biology, mitosis is the process of chromosome segregation and nuclear division that follows replication of the genetic material in eukaryotic cells. This process assures that each daughter nucleus receives a complete copy of the organism's genome. In most eukaryotes mitosis is accompanied with cell division or cytokinesis, but there are many exceptions, for instance among the fungi. There is another process called meiosis, in which the daughter nuclei receive half the chromosomes of the parent, which is involved in gamete formation and other similar processes. The term clone is derived from κλων, the Greek word for "twig". k, b. In horticulture, the spelling clon was used until the twentieth century. The final e came into use to indicate the vowel is a "long o" instead of a "short o"; see the references below on this point. Since the term entered the popular lexicon in a more general context, the spelling clone.

They may be frozen for long periods of time. Even if 90% of the cells are killed by the freezing process, there are millions of cells in a milliliter of liquid culture. Demonstrating that adaptive mutations arise from preadaptation rather than directed mutation. For this purpose, they invented replica plating Replica plating is a technique in which multiple dishes, also known as Petri plates, containing solid (agar-based) microbial media, are inoculated with between thirty and three-hundred colonies of microorganisms from a primary plate (or master dish), reproducing the original spatial pattern of colonies. The technique involves pressing a velvet-covered disk to a primary plate, and then imprinting ..... Click the link for more information. , which allowed them to transfer numerous bacterial colonies In biology, a colony (from Latin colonia) means several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defences, the ability to attack bigger prey etc. Some insects (ants, for example) live only in colonies. Colonies were probably the first step towards multicellular organisms during evolution. The difference between a multicellular organism and a colony is that individual organisms from a colony can, if separated, survive on their own, while cells from a multicellular lifeform (e.g., liver cells) cannot. Volvox is an example for the border between these two states from their specific locations on one agar-filled petri dish to analogous locations on several other petri dishes. After replicating a plate of E. coli, they exposed each of the new plates to phage

A phage (also called bacteriophage) is a small virus that infects only bacteria. Like viruses that infect eukaryotes, phages consist of an outer protein hull and the enclosed genetic material (which consists of double-stranded DNA in 95% of the phages known) of 5 to 650 kbp (kilo base pairs) with a length of 24 to 200 nm. The vast majority of phages (95%) have a tail to let them inject their genetic material into the host. Phages were discovered independently by Frederick Twort in 1915 and by Félix d’Herelle in 1917. d'Herelle continued his research and development in Stalin's Soviet Union.  They observed that phage-resistant colonies were present at analogous locations on each of the plates, allowing them to conclude that the phage resistance trait had existed in the original colony, which had never been exposed to phage, instead of arising after the bacteria had been exposed to the virus.

The oxazolidinone class was discovered by researchers at EI duPont de Nemours and reported in 1987. Pharmacia Corporation developed linezolid and FDA approval was granted in April 2000. It is sold in the US under the tradename Zyvox in either tablet form, oral suspension powder, or in an inactive medium for intravenous injection.

Side effects include rashes, loss of appetite, diarrhea, nausea, constipation and fever. A small number of patients will incur a severe allergic reaction, or tinnitis, or pseudomembranous colitis, or thrombocytopenia. Linezolid is a weak monoamine oxidase inhibitor (MAOI) and cannot be used with tyramine containing foods or pseudoephedrine.

ß-lactams are generally considered concentration-independent killers of bacteria. Both in vitro and animal data support T>MIC as a pharmacodynamic parameter that predicts activity, though other parameters take on increased importance in select settings. A relatively large body of data from human studies supports administering these agents as a continuous infusion or in shorter dosage intervals, especially in neutropenic patients, to maximize the interval during which drug concentration is kept above the MIC. However, no convincing data are available to support choosing continuous infusions over more conventional dosing schemes in the majority of clinical situations. In addition, whereas limited clinical data have speculated on the optimal duration of T>MIC, definitive values have yet to be established. Clearly, more in vitro and much more human data are needed to validate the importance of T>MIC across the spectrum of infectious diseases.

Aminoglycosides are a group of antibiotics that are effective against certain types of bacteria. They include amikacin, gentamicin, kanamycin, neomycin, netilmicin, paromomycin, streptomycin, and tobramycin. Those which are derived from Streptomyces species are named with the suffix -mycin, while those which are derived from micromonospora are named with the suffix -micin.

Aminoglycosides work by binding to the bacterial 30S ribosomal subunit, causing misreading of t-RNA, leaving the bacterium unable to synthesize proteins vital to its growth.

Aminoglycosides are useful primarily in infections involving aerobic, Gram-negative bacteria, such as Pseudomonas, Acinetobacter, and Enterobacter. In addition, some mycobacteria, including the bacteria that cause tuberculosis, are susceptible to aminoglycosides. Streptomycin was the first effective drug in the treatment of tuberculosis, though the role of aminoglycosides such as streptomycin and amikacin have been eclipsed (because of their toxicity and inconvenient route of administration) except for multiple drug resistant strains.

Infections caused by Gram-positive bacteria can also be treated with aminoglycosides, but other types of antibiotics are more potent and less damaging to the host. In the past the aminoglycosides have been used in conjunction with penicillin-related antibiotics in streptococcal infections for their synergistic effects, particularly in endocarditis.

Because of their potential for ototoxicity and renal toxicity, aminoglycosides are administered in doses based on body weight. Blood drug levels and creatinine are monitored during the course of therapy.

Another important consideration in pharmaco-dynamics is the presence or absence of a PAE, which refers to the ability to suppress bacterial growth after a scripted exposure to an antibiotic. In general, ß-lactams produce a PAE only against gram-positive organisms, although some authors suggest the class, especially carbapenems, have a sustained PAE (as well as concentration-dependent activity) against gram-negative organisms. Only agents that interrupt protein or nucleic acid synthesis, such as the macrolides, fluoroquinolones, and aminoglycosides, have been consistently shown to produce a sustained PAE against gram-negative bacteria.

Translating the PAE found with in vitro experiments into a treatment for human infections is potentially problematic. Frequently, the PAE is longer in vivo than in vitro, but in some cases it may be nonexistent in vivo, as is the case with streptococci exposed to penicillins and cephalosporins. Although in vitro PAE data are often generated after single antibiotic exposures and therefore do not simulate a clinical course of multiple antibiotic treatments, clinicians are dependent on literature values because this type of laboratory testing is not routinely done. In summary, the PAE is unique to the pathogen and is generally longer in vivo than in vitro. The PAE may wane with multiple dosing and is not a clinically reported value. Therefore, justifying extended dosage intervals based on PAE is difficult.

There is no oral form of these antibiotics: they are generally administered intravenously, though some are used in topical preparations used on wounds.

Aminoglycosides are completely ineffective against anaerobic bacteria, fungi and viruses.

The MIC portion of this test procedure begins with diluting the test product serially with equal volumes of 2X growth media. The resulting suspensions are 1X growth media with decreasing concentrations of the test product. The dilutions increase in such a way that the next dilution is half as concentrated as the dilution before (i.e. 1:2, 1:4, 1:8, 1:16:, 1:32...). Each dilution is then spiked with 0.05 mL of test culture and the dilutions are incubated.

It is important to keep in mind that MIC cannot be determined without following up with an MLC test. After incubation, the MIC dilution tubes will either be turbid with growth or they will be clear. A tube without turbid growth will result from one of two possible events. Either the challenge microorganisms were killed by the test product, or they were inhibited by the test product. Negative tubes that are suspected of having inhibited microorganisms are subcultured in neutralizer broth. The neutralizer broth tubes are then incubated and scored for growth. A subculture tube that becomes turbid after incubation indicates that the test product was inhibitory at that dilution for that particular organism. If the subculture tubes remain negative after incubation, this indicates that the test product is lethal at that concentration for that particular organism.

Test products that are not clear or precipitate the growth media follow the same basic test procedure described above, but in order to detect growth of the test organisms, each dilution must be plated onto agar and incubated.

An antibiotic is a drug This article is about chemical substances. For other meanings of the word "drug", see Drug (disambiguation) A drug is any substance that can be used to treat an illness, relieve a symptom, or modify a chemical process or processes in the body. The word "drug" is ethymologically derived from the Dutch/Low German word "droog", which means "dry", since in the past, most drugs were dried plant parts. ..... Click the link for more information. that kills or slows the growth of bacteria

Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae. Antibiotics are one class of "antimicrobials", a larger group which also includes anti-viral, anti-fungal, and anti-parasitic drugs. f, h, c. They are relatively harmless to the host, and therefore can be used to treat Therapy or treatment is the remediation of a health problem, after the diagnosis. Types of therapy include:

drug therapy, in which drugs are used to treat an issue massage therapy occupational therapy physical therapy (physiotherapy) psychotherapy, where combinations of drugs and communications are used to treat mental health or personality development issues. radiation therapy recreational therapy speech therapy surgery alternative forms such as crystal therapy

"Infection" is also the title of an episode of the television series Babylon 5; see Infection (Babylon 5). An infection is the detrimental colonization of a host organism by a foreign species. The colonizing organism interferes with the normal functioning and perhaps the survival of the host. The infecting organism is referred to as a pathogen, which may be bacterial, a parasite, fungal, or a virus, prion or viroid. The scientific study of diseases in medicine caused by biological agents is infectious diseases. The term originally described only those formulations derived from living organisms, but is now applied also to synthetic antimicrobials, such as the sulfonamides Sulfonamides, also known as sulfa drugs, are synthetic antimicrobial agents derived from sulfonic acid. In bacteria, these drugs are competitive inhibitors of para-aminobenzoic acid (PABA), a substrate of the enzyme dihydropteroate synthetase. This reaction is necessary in these organisms for the synthesis of folic acid.