Contagious equine metritis: isolation and characterization of the etiologic agent

Uterine, cervical, and clitoral specimens on swabs from pony mares infected with contagious equine equine metritis (CEM) bacteria were streaked on agar plates. Colonies of CEM bacteria were observed under CO2 incubation in 2 days on Eugon chocolate agar and Eugon blood agar plates. The diameter of the colonies varied from 0.2 mm to 1 mm in 2 days which increased to 0.3 mm to 2.0 mm on day 4. The colonies on Eugon chocolate agar plates on days 2 to 4 were shiny, brown, round, and convex, and easily glided when pushed with a loop. The diameter of the colonies on chocolate and blood agar plates made from tryptose blood agar base (TrCA or TrBA) was 0.2 to 0.3 mm on day 4. Due to their small size on TrCA or TrBA, colonies of CEM bacteria were easily recognized from large numbers of contaminants. The organism required hemin for its growth. It gelled in water, caused delayed hemolysis of blood agar plates, and was extremely susceptible to acid in the pH range to 3 to 4.5. A difference in growth of CEM bacterium was observed on primary isolation media obtained from two different commerical sources.