As a result of the organism going through several doubling generations of growth before inhibition, a haze of bacterial growth occurs on the agar around the disk. This phenomenon, which should be ignored, can be observed when testing which class of antibiotics?
a. Aminoglycosides
b. Sulfonamides
c. Penicillins
d. Cephalosporins
B
Hazes of bacterial growth may be observed when testing sulfonamides and trimethoprim because the organism population goes through several doubling generations before inhibition; the resulting haze of growth should be ignored for disk interpretation with these agents. Similarly, Proteus spp. may swarm over the surface of the plate complicating measurement of zone boundaries. In both cases, the hazes of growth should be ignored and zone diameters measured at the point where growth is obviously inhibited.
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