Lab Report 11. Kirby-Bauer Dise Assay (10 points) 1. (1 point) Fill out Table 1

Question

Lab Report 11. Kirby-Bauer Dise Assay (10 points) 1. (1 point) Fill out Table 1 Table 1. Antibiotic discs. Antibiotics Amount (Hg or U/EUUD Bacitracin Clindam Na 2. (2 points) Fill out Table 2 Table 2. Kirby-Bauer dise assay: zone of growth inhibition. Report the Zone of inhibition (mm). Report whether the organism is susceptible (S) Intermediate () or resistant (R) to each of the antibiotic. Antibiotics E coli B. subtilus S.marcesens S. epidermidis Bacitracin Clindamycin Nalidixic acid Novobiocin Polymyxin B Onm 85 3. (3.5 points) Which antibiotic(s) showed the broadest spectrum? And suggest a reasonable hypothesis that can explain such property of that antibiotic. 4. 3.5 points) Which strain(s) is generally the most resistant to antibiotic (based on your results)? And suggest a reasonable hypothesis that can explain such phenomenon.

Explanation / Answer

This is an antibiotic sensitivity test. In this experiment, there have been different antibiotics used, in order to check the spectrum of the antibiotics. It is used to identify if the antibiotic is broad spectrum or narrow spectrum, in which if the antibiotic is effective against both Gram positive or Gram negative bacteria, or if the antibiotic is effective against only one class is tested. This is done by the disk diffusion method, in which the discs of different concentration of antibiotics will be used. The agar would be spread by each of the organisms in four different quadrants, and the circular zone of inhibition if the bacteria would be identified. The antibiotic showing broadest spectrum would be showing zone of inhibition with all of the four bacteria. The antibiotic showing broadest spectrum in this case is Novobiocin, that shows zone against all the four bacteria. Based on the results, the most resistant strain is S.marcesens showing on,y 9mm zone and most sensitive is S.epidermidis showing 40mm of zone.

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