Evaluation of the Rapid ID 32A system for the identification of the Bacteroides fragilis group

OBJECTIVE: To evaluate the use of a rapid identification system, Rapid ID 32A (bioMérieux), for the identification of clinically important species in the B. fragilis group. METHODS: The use of Rapid ID 32A was validated on 249 clinical isolates, all of which were tested by conventional techniques, and in selected instances API 20A. Rapid ID 32A (and API 20A as appropriate) was then applied in a central laboratory to the identification of 1289 B. fragilis group clinical isolates from 22 laboratories in 15 European countries. RESULTS: Improvements in the initial database permitted the accurate identification of isolates of B. fragilis, B. thetaiotaomicron and B. vulgatus, but further tests, especially for catalase production, were required to distinguish between B. ovatus and B. uniformis, while an identification of B. distasonis could be accepted only after careful review of results. There were too few isolates of B. caccae, B. merdae and B. stercoris for us to reach satisfactory conclusions, but further tests are clearly necessary. CONCLUSIONS: The study emphasizes the importance of including sufficient numbers of isolates of different species in the validation of identification methods. Rapid ID 32A is a reliable system for the identification of the common species in the B. fragilis group, especially B. fragilis and B. thetaiotaomicron.