Q 1. E.coli and S.epidermidis were chosen to represent Gram-negative and Gram-positive bacteria, respectively. For a given antibiotic, is there a difference in susceptibility between the Gram-positive and Gram-negative bacteria? If so, what difference(s) do you see?
Q 2. Suppose you do this test on a hypothetical Staphylococcus species with the antibiotics penicillin (P-10) and chloramphenicol (C30). You record zone identical diameters of 25 mm for the chloramphenicol and penicillin disks. Which antibiotic would be more effective against this organism? What does this tell you about comparing zone diameters to each other and the importance of the zone diameter interpretive chart?
Q 3. How does the antibiotic get from the disk into the agar?