Lab Report: Antibiotic Evaluation by the Kirby-Bauer Method Essay

2252 Words Mar 21st, 2013 10 Pages
Lab Report: Antibiotic Evaluation by the Kirby-Bauer Method


Chemical antimicrobial agents are chemical compounds capable of either inhibiting the growth of microorganisms or killing them outright. Those which are taken internally to alleviate the symptoms of or promote healing from disease are called chemotherapeutic drugs, and among these is a class of compounds called antibiotics. In order for a chemotherapeutic drug to be classed as an antibiotic, it must be produced by a microorganism such as bacterium or fungus or at least derived from a chemical produced by one. It must also be capable of killing or inhibiting the growth of other microorganisms and of doing so when taken in very small quantities. To study
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It also has a low toxicity threshold when ingested, and so it is now used almost exclusively to combat life-threatening illness or infection. (DrugBank)
Erythromycin, which is produced by a Streptomyces and functions as a protein synthesis inhibitor in much the same way as Chloramphenicol. It is much less toxic than Chloramphenicol and is used to combat such diseases as whooping cough, diptheria, and pelvic inflammation due to syphilis. (DrugBank)
Novobiocin, one of the aminoglycoside antibiotics. This class of antibiotics works by binding to the bacterial 16S rRNA and causing the misreading of tRNA. Because of this, the bacteria synthesizes incomplete or toxic polypeptides, resulting in the death of the bacterial cell. Novobiocin can be used to treat infection by Gram negative bacteria and Mycobacteria, including Mycobacterium tuberculosis. It is not effective against anaerobic bacteria, however, and is not often used against Gram positive infections because other antibiotics that are less toxic to the patient are available for this purpose. (DrugBank) Moreover, Novobiocin is known to bind to and alter the function of DNA gyrase, effectively stopping proper replication in the bacterial cell and thus bactericidal.
Penicillin G, another antibiotic of the beta lactam class. It is used primarily against Gram positive bacteria such as the Streptococci but is also effective against some Gram negatives such as Neisseria

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