A microbiologist is reading a vaginal culture on the bench. There is growth on the SBA and chocolate (CHOC) plates, but no growth on the MacConkey (MAC) plate. The colonies growing on the SBA have produced a narrow, diffuse zone of $\beta$-hemolysis around and under the colonies. What organism could this be?
A) Escherichia coli
B) Streptococcus agalactiae
C) Streptococcus pyogenes
D) Streptococcus pneumoniae

Question

Quizplus · Accepted Answer

The growth on SBA and CHOC plates indicates the organism is a facultative anaerobe. The absence of growth on MAC plate suggests that the organism is not a lactose fermenter. The narrow, diffuse zone of F1F1F1S1F1F1F10-hemolysis suggests the organism is a Group B Streptococcus which is known to produce this type of hemolysis. Therefore, the best choice is Streptococcus agalactiae.

A Microbiologist Is Reading a Vaginal Culture on the Bench β\betaβ

A Microbiologist Is Reading a Vaginal Culture on the Bench $\beta$