Material from an intestinal abscess produces gray colonies with a brown color in the area around the colonies on a BBE plate incubated anaerobically. There is also a dark precipitate in the medium in the areas of heavy growth. A Gram stain of the colonies reveals gram-negative coccobacilli. What is the presumptive identification of this organism?

Question

Quizplus · Accepted Answer

The gray colonies with a brown color around them and dark precipitate in the medium are characteristic of Bacteroides fragilis. In addition, B. fragilis is a common cause of intestinal abscesses and is a gram-negative coccobacillus. The other organisms listed are either not commonly associated with intestinal abscesses or have different characteristics on BBE plates.

Material from an Intestinal Abscess Produces Gray Colonies with a Brown