18) You are given a prepared slide to observe under the microscope. At the 10x y

Question

18) You are given a prepared slide to observe under the microscope. At the 10x you ca . n note the dimensions of the specimen being 500 micrometers by 300 micrometers. What domain do you believe the microbe belongs to? L_19) Suppose we have a patient come in with a hemolytic virus, we take a sample from the patient and perform a serial dilution on a red blood çell line. Suppose we calculated 37 plaques at a dilution factor of 102 and the volume plated was 0.1mL of sample. Calculate the number of PFUs in the patient's initial sample. . ,-20) Suppose we used the following antibiotic wafers for a Kirby-Bauer test: AMX-5, AMX-10, AMX-15, AMX-20, AMX-25. Which wafer do you expect to kill the most bacteria and why? 21) Thinking of the MacConkey plate we know it was both selective and differential. What was it differentiating and how was the plate able to do this?

Explanation / Answer

20. AMX-25 (amoxycillin 25 micrograms or milligrams) kills most number of bacteria. As the antibiotic concentration is more, it diffuses into large area in the medium and kills more bacteria.

21. Mac Conkey media contains Lactose as one of its ingredients. It also contains indicator Neutral Red which turns pink when pH becomes acidic. Mac Conkey differentiates betwen lactose fermenting and non fermenting bacteria. When a bacteria ferments lactose, acidic pH is produced. The colony turns pink. Non fermenting colonies appear pale in color.

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