The direct immunofluorescence in the presumptive identification of Bacteroides species.

Two kits containing fluorescein labeled-polyvalent antisera to Bacteroides fragilis, Bacteroides distasonis, Bacteroides ovatus, Bacteroides thetaiotaomicron, Bacteroides vulgatus (Fluoretec-F) and to Bacteroides melaninogenicus subsp. melaninogenicus and intermedius and to Bacteroides asaccharolyticus (non-oral strains) (Fluoretec-M) were evaluated for the identification of the respective organisms in bacterial cultures and clinical specimens. In both cases immunofluorescent tests were compared to the bacteriological data. The results clearly demonstrated that Fluoretec-F has a specificity 97% and a sensitivity 96%. The corresponding values for Fluoretec-M were 99% and 87.5% respectively, either clinical specimens or pure cultures were examined. The presence of aerobic of facultative anaerobic bacteria and obligate anaerobic bacteria other than those to which antisera were included in the test kits did not seem to influence the test result. No cross-reactivity between Fluoretec-F and -M were observed. Also, no positive fluorescence was obtained when other anaerobic bacteria than Bacteroides spp. were tested. The same was also the case with various aerobic or facultative anaerobic bacteria. The use of Fluoretec-F and -M is considered as a useful tool for the early accurate identification of the Bacteroides species mentioned, which may serve as a guide for an appropriate prompt therapy which is especially needed in serious anaerobic infections.