Question

mpare compe the TSA/NA plates in Table 2. Then, decide and racord if the antibiotic is D Table 2: Degree of Antibiotic Effect on Test Organisms Penicillin Trimethoprim -static or -cidal -static or -cidal Chloramphenicol are REDOX Ciprofloxicin NG/G -static or -cidal static or -cidal NG/G NG/G Organism NG/G he differe E. coli S. aureus e steps QUESTIONS n gly All aspects of the Kirby-Bauer test are standardized to assurer reliability deep? a. What might be the consequence of pouring the plates 2 mm deep instead of 4 mm w b. The Mueller-Hinton II plates upposed to be used within a specific time after their preparation and are should be free of visible moisture. What negative effect(s) might mnoisture have on the test? SECTION 7 Medical Microbiology

Answer 1

All aspects of the Kirby-Bauer test are standardized to assure reliability

a. What might be the consequence of pouring the plates 2 mm deep intstead of 4 mm deep?

Answer - This would affect the distance the antibiotic diffuses from the disk. The thicker the agar, the more downward diffusion there is and the less antibiotic available to diffuse outward. Thus, the zone would be smaller.

b. The Mueller-Hinton II plates are supposed to be used within a specific time after their preparation and should be free of visible moisture. What negative effect(s) might moisture have on the test?

Answer - The older the plates, the drier they become. This could affect the ability of the antibiotic to diffuse through the agar. Moisture might help spread the antibiotic further than diffusion alone.