Quiz 4

Question 1

Describe in detail, how beta lactams kill bacterial cells.

Answer 1

Beta-lactams prevent amino acid crossbridges from forming between NAG and NAM subunits of peptidoglycan, causing lysis of the cell. Beta-lactams work best during the log phase of growth (they do not work on peptidoglycan that has already been formed). Beta-lactams include penicillin and other semi-synthetics.

Question 2

Antimicrobial activity can be measured by determing the smallest amount of agent needed to inhibit the growth of a test organism, an assay called the ________.

Answer 2

MIC

Minimum Inhibitory Concentration

Question 3

Describe, in detail, the disk diffusion assay.

Answer 3

Disk diffusion uses an antimicrobial soaked disk that is placed on top of a heavily inoculated MHA (Muller-Hinton Agar) plate. Muller Hinton agar is not selective and a “loose” agar that allows for diffusion. The plate is incubated then, if present, the zone of inhibition is measured. The zone of inhibition indicates if the microorganism is sensative, resistant, or intermediate.