Kirby Bauer Experiment

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Bacterial growth may be controlled by many methods; the techniques relevant to this experiment include heat, ultraviolet (UV) light, and antimicrobial control. Using heat as a means of controlling bacterial growth is favorable because it is quick, safe, and cost-effective (Nester, 2007). There are two kinds of heat: moist heat, which destroys the proteins of microorganisms by boiling or steaming, and dry heat, which requires high temperatures to oxidize cell components and damage proteins by incineration or dry heat ovens (Nester, 2007). Cellular proteins are essential in carrying out important biological activities, so without them, the bacteria will not be able to survive (Nester, 2007). Moist heat is widely used to treat drinking water, …show more content…

The Kirby-Bauer test was developed in the 1950s by W. Kirby and A. Bauer and their co-workers as a form of susceptibility testing; in 1961, the test was standardized by the World Health Organization (Reynolds, 2001). The purpose of the Kirby-Bauer test is to determine whether bacteria are susceptible, intermediate, or resistant to a specific antibiotic (Hudzicki, 2013). A filter paper is soaked with the antibiotic and placed on an agar plate; after it is incubated, the diameter of the zone of inhibition (area of no bacterial growth around the filter paper) is measured and compared to a standard zone chart to determine the susceptibility of the bacteria to the specific antibiotic (Hudzicki, …show more content…

Streptomycin is part of the category of aminoglycosides (Nester, 2007). Aminoglycosides and tetracyclines affect the ribosomes of bacterial cells; aminoglycosides block the initiation phase of translation during protein synthesis, which causes a misreading of mRNA, and tetracycline blocks the attachment of tRNA to the ribosome of the bacterial cell (Nester, 2007). Aminoglycosides also have a low therapeutic index, meaning it can be harmful to humans (Nester, 2007). Streptomycin is often used for treating tuberculosis and tetracycline is used for a variety of bacterial infections, including Lyme disease and syphilis (Nester, 2007). Penicillin includes a family of antimicrobial medications that interfere with the cell wall synthesis of bacteria; penicillin often treats pneumonia and UTIs, for instance (Nester, 2007). Erythromycin prevents the continuation of protein synthesis, and is often the drug of choice for people that are allergic to penicillin, and thus has similar uses (Nester, 2007). Chloramphenicol is a broad-spectrum antibiotic that prevents peptide bonds from being formed in bacterial cells; it has a low therapeutic index, however, so it is used a last-resort drug (Nester, 2007). Lincomycin has the same mechanism of bacterial growth control as chloramphenicol and is often used to treat severe bacterial infections. There were

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