Evaluation of xylan fermentation for the identification of Bacteroides ovatus and Bacteroides thetaiotaomicron.

The reliability of xylan fermentation in distinguishing Bacteroides ovatus from Bacteroides thetaiotaomicron was examined with strains previously identified by DNA homology studies or bacteriophage sensitivity testing or both. All of the 12 B. ovatus strains produced acid ranging from pH 5.0 to 5.6 in peptone-yeast-xylan broth; none of the 19 B. thetaiotaomicron strains produced acid, and the final pH was 6.0 or 6.1. Xylan fermentation and bacteriophage sensitivity-DNA homology appear to be equivalent in their ability to differentiate these two Bacteroides species.