antibiotics classification and mechanism of action pdf

Antibiotics Classification And Mechanism Of Action Pdf

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Compare the two classes of antibiotics: bactericidal and bacteriostatic antibiotic.

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Overview of antibiotic therapy

Antibiotic , chemical substance produced by a living organism, generally a microorganism, that is detrimental to other microorganisms. Antibiotics commonly are produced by soil microorganisms and probably represent a means by which organisms in a complex environment , such as soil, control the growth of competing microorganisms.

Microorganisms that produce antibiotics useful in preventing or treating disease include the bacteria and the fungi. Antibiotics came into worldwide prominence with the introduction of penicillin in Since then they have revolutionized the treatment of bacterial infections in humans and other animals.

They are, however, ineffective against viruses. In Scottish bacteriologist Alexander Fleming noticed that colonies of bacteria growing on a culture plate had been unfavourably affected by a mold , Penicillium notatum , which had contaminated the culture.

A decade later British biochemist Ernst Chain , Australian pathologist Howard Florey , and others isolated the ingredient responsible, penicillin, and showed that it was highly effective against many serious bacterial infections.

Toward the end of the s scientists experimented with the addition of various chemical groups to the core of the penicillin molecule to generate semisynthetic versions. A range of penicillins thus became available to treat diseases caused by different types of bacteria, including staphylococci , streptococci , pneumococci , gonococci, and the spirochaetes of syphilis. Conspicuously unaffected by penicillin was the tubercle bacillus Mycobacterium tuberculosis.

This organism, however, turned out to be highly sensitive to streptomycin , an antibiotic that was isolated from Streptomyces griseus in As well as being dramatically effective against tuberculosis , streptomycin demonstrated activity against many other kinds of bacteria, including the typhoid fever bacillus.

Two other early discoveries were gramicidin and tyrocidin, which are produced by bacteria of the genus Bacillus. In the s researchers discovered the cephalosporins , which are related to penicillins but are produced by the mold Cephalosporium acremonium. The following decade scientists discovered a class of antibiotics known as quinolones.

Quinolones interrupt the replication of DNA —a crucial step in bacterial reproduction—and have proven useful in treating urinary tract infections , infectious diarrhea , and various other infections involving elements such as bones and white blood cells.

The principle governing the use of antibiotics is to ensure that the patient receives one to which the target bacterium is sensitive, at a high enough concentration to be effective but not cause side effects, and for a sufficient length of time to ensure that the infection is totally eradicated. Antibiotics vary in their range of action. Some are highly specific. Others, such as the tetracyclines , act against a broad spectrum of different bacteria. These are particularly useful in combating mixed infections and in treating infections when there is no time to conduct sensitivity tests.

While some antibiotics, such as the semisynthetic penicillins and the quinolones, can be taken orally, others must be given by intramuscular or intravenous injection. Antibiotics can be categorized by their spectrum of activity—namely, whether they are narrow-, broad-, or extended-spectrum agents. Narrow-spectrum agents e. Broad-spectrum antibiotics, such as tetracyclines and chloramphenicol , affect both gram-positive and some gram-negative bacteria.

An extended-spectrum antibiotic is one that, as a result of chemical modification, affects additional types of bacteria, usually those that are gram-negative. The terms gram-positive and gram-negative are used to distinguish between bacteria that have cell walls consisting of a thick meshwork of peptidoglycan [a peptide-sugar polymer] and bacteria that have cell walls with only a thin peptidoglycan layer, respectively. Some common antibiotics are listed in the table. Antibiotics produce their effects through a variety of mechanisms of action.

Production of the bacterial cell wall involves the partial assembly of wall components inside the cell, transport of these structures through the cell membrane to the growing wall, assembly into the wall, and finally cross-linking of the strands of wall material.

Antibiotics that inhibit the synthesis of the cell wall have a specific effect on one or another phase. The result is an alteration in the cell wall and shape of the organism and eventually the death of the bacterium. Other antibiotics, such as the aminoglycosides , chloramphenicol, erythromycin , and clindamycin, inhibit protein synthesis in bacteria. The basic process by which bacteria and animal cells synthesize proteins is similar, but the proteins involved are different. Those antibiotics that are selectively toxic utilize these differences to bind to or inhibit the function of the proteins of the bacterium, thereby preventing the synthesis of new proteins and new bacterial cells.

Antibiotics such as polymyxin B and polymyxin E colistin bind to phospholipids in the cell membrane of the bacterium and interfere with its function as a selective barrier; this allows essential macromolecules in the cell to leak out, resulting in the death of the cell. Because other cells, including human cells, have similar or identical phospholipids, these antibiotics are somewhat toxic.

Some antibiotics, such as the sulfonamides , are competitive inhibitors of the synthesis of folic acid folate , which is an essential preliminary step in the synthesis of nucleic acids. Sulfonamides are able to inhibit folic acid synthesis because they are similar to an intermediate compound para-aminobenzoic acid that is converted by an enzyme to folic acid. The similarity in structure between these compounds results in competition between para-aminobenzoic acid and the sulfonamide for the enzyme responsible for converting the intermediate to folic acid.

This reaction is reversible by removing the chemical, which results in the inhibition but not the death of the microorganisms. One antibiotic, rifampin , interferes with ribonucleic acid RNA synthesis in bacteria by binding to a subunit on the bacterial enzyme responsible for duplication of RNA.

Since the affinity of rifampin is much stronger for the bacterial enzyme than for the human enzyme, the human cells are unaffected at therapeutic doses. Antibiotic Article Media Additional Info. Article Contents. Print print Print. Table Of Contents. While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. Facebook Twitter.

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The Editors of Encyclopaedia Britannica Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree See Article History. Learn how to effectively use antibiotics.

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Action and resistance mechanisms of antibiotics: A guide for clinicians

Phototoxicity Achilles tendon rupture Impaired fracture healing. Thrombocytopenia Avoid in third trimester of pregnancy. Bacillus anthracis Bacillus cereus Clostridium tetani Clostridium botulinum Clostridium perfringens Clostridium difficile. Average 4. Tested Concept.

Antibiotic , chemical substance produced by a living organism, generally a microorganism, that is detrimental to other microorganisms. Antibiotics commonly are produced by soil microorganisms and probably represent a means by which organisms in a complex environment , such as soil, control the growth of competing microorganisms. Microorganisms that produce antibiotics useful in preventing or treating disease include the bacteria and the fungi. Antibiotics came into worldwide prominence with the introduction of penicillin in Since then they have revolutionized the treatment of bacterial infections in humans and other animals. They are, however, ineffective against viruses.

Written and peer-reviewed by physicians—but use at your own risk. Read our disclaimer. Antibiotics are a class of drugs employed mainly against bacterial infections. Some antibiotics are also used against parasitic infections. Antibiotics can have bacteriostatic i. Antibiotics are effective against either a small group of bacteria narrow-spectrum or a wide range of pathogens broad-spectrum. Most antibiotics work by inhibiting cell wall synthesis, protein synthesis , or certain enzymes e.

List of antibiotics

Infections account for a major cause of death throughout the developing world. This is mainly due to the emergence of newer infectious agents and more specifically due to the appearance of antimicrobial resistance. With time, the bacteria have become smarter and along with it, massive imprudent usage of antibiotics in clinical practice has resulted in resistance of bacteria to antimicrobial agents. The antimicrobial resistance is recognized as a major problem in the treatment of microbial infections. Determination of bacterial resistance to antibiotics of all classes phenotypes and mutations that are responsible for bacterial resistance to antibiotics genetic analysis are helpful.

Antibiotics : Classification and mechanisms of action with emphasis on molecular perspectives

Antibiotic

Each issue covers review articles on Drug discovery topics, and also publishes full-length reviews related to different subjects in pharmacy and that are of broad readership interest to users in industry, academia, and government. The first issue was published online in December All contributions to Sys. Rev Pharm are reviewed by the peer review process and copyediting process with the understanding that they have not been published previously and are not under consideration for publication elsewhere. Scope of the journal.

Image-based screening has become a mature field over the past decade, largely due to the detailed information that can be obtained about compound mode of action by considering the phenotypic effects of test compounds on cellular morphology. However, very few examples exist of extensions of this approach to bacterial targets. We now report the first high-throughput, high-content platform for the prediction of antibiotic modes of action using image-based screening. This approach employs a unique feature segmentation and extraction protocol to quantify key size and shape metrics of bacterial cells over a range of compound concentrations, and matches the trajectories of these metrics to those of training set compounds of known molecular target to predict the test compound's mode of action. This approach has been used to successfully predict the modes of action of a panel of known antibiotics , and has been extended to the evaluation of natural products libraries for the de novo prediction of compound function directly from primary screening data.

The following is a list of antibiotics. The highest division between antibiotics is bactericidal and bacteriostatic. Bactericidals kill bacteria directly, whereas bacteriostatics prevent them from dividing. However, these classifications are based on laboratory behavior. In practice, both can effectively treat a bacterial infection.


Antibiotics: Classification and mechanisms of action. with emphasis on molecular perspectives. Ebimieowei Etebu1* and Ibemologi Arikekpar2.


Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. Etebu and I. Etebu , I. Arikekpar Published Chemistry.

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