Comparative serology of two clinical isolates of Bacteroides fragilis and Bacteroides thetaiotaomicron.

Antiserum prepared in rabbits against Bacteroides fragilis showed numerous bands when reacted with B. fragilis antigen in Ouchterlony plates. This antiserum also reacted with Bacteroides thetaiotaomicron and showed one band of apparent identity with B. fragilis. The band of identity common for both organisms was lost if the antigen was heated at 80 degrees C for 30 min. Antisera prepared against B. thetaiotaomicron did not react with B. fragilis.