What Do Aeromonad Colonies Look Like on Cefsulodin-Irgasan-Novobiocin (CIN) Agar

Question

What do aeromonad colonies look like on cefsulodin-irgasan-novobiocin (CIN) agar?
A) Purple colonies
B) Clear colonies
C) Green colonies
D) Pink colonies

Accepted Answer

Aeromonad colonies appear as pink colonies on CIN agar due to their ability to ferment lactose, which causes acid production that lowers the pH of the agar and results in the pink color. Cefsulodin, irgasan, and novobiocin are antibiotics incorporated into the agar to inhibit the growth of competing bacteria and select for the growth of Aeromonas spp.