The Effects of Antibiotics - Lab Report Example

Introduction Bacteria are the minutest disease causing organisms. Most of the diseases we study about are caused by bacterial infections e.g. tuberculosis is caused by mycobacterium tuberculin. For the eradication and elimination antibiotics and antiseptics were invented. Both of these are chemical agents but differ in mode of actions Antibiotics are either bacteriostatic, which means they stop bacterial multiplication or they are bactericidal, meaning they kill the bacteria. To understand the actions of antibiotics a test called Kirby-Bauer is conducted.

(merckmanuals.com)Materials and MethodsThe Kirby-Bauer or disc diffusion method is conducted which tests antibiotic susceptibility. In this method inhibition of bacterial growth is measured closely. The requirements for this test are a culture medium and filter discs containing antibiotics. ProcedureThe discs are impregnated with a particular antibiotic. The organism will grow on the culture plate while the antibiotic works to prevent the growth. If the organism is susceptible, there will be no growth around the disc containing the antibiotic.

The size of the zone of inhibition formed around the filter discs indicates the degree of sensitivity of particular bacteria to a drug. The interpretation of the test is the bigger the area of bacteria-free media surrounding a disc means the bacteria are more sensitive to the drug the disc contains. According to a criteria set by the National Committee for Clinical Laboratory Studies (NCCLS)organisms are classified into Resistant (R), Intermediate (I) or Susceptible (S).(aminj.myweb.uga.edu)ResultsThe particular antibiotic stops the growth of the bacteria.

After the diffusion of the bacteria on the culture medium, circular spots were observed. These spots were the areas on which bacterial growth did not occur. (microbelibrary.org)Cefmatazole is the most susceptible drug according to the test. Penicillin and ampicillin are lesser susceptible than cefmatazole and gentamycin is the least susceptible. Penicillin and ampicillin are resistant antibiotics.ConclusionAntibiotics prove to be bactericidal for antibiotics and stop their growth because they are sensitive.

ReferencesSusceptibility Testing.(n.d.). : Laboratory Diagnosis of Infectious Disease: Merck Manual Professional. http://www.merckmanuals.com/professional/infectious_diseases/laboratory_diagnosis_of_infectious_disease/susceptibility_testing.html?qt=kirby%20bauer&alt=shKIRBY-BAUER.(n.d.). KIRBY-BAUER. Retrieved June 29, 2014, from http://aminj.myweb.uga.edu/KIRBY-BAUER.htmlKirby-Bauer Disk Diffusion Susceptibility Test Protocol.(n.d.). Kirby-Bauer Disk Diffusion Susceptibility Test Protocol.

http://www.microbelibrary.org/component/resource/laboratory-test/3189-kirby-bauer-disk-diffusion-susceptibility-test-protocol