Bacteroides fragilis constitutes about 1 to 2% of the normal colon flora in humans; however, this bacterium is the most commonly encountered bacterium from anaerobic infections due to its several virulence factors. Some strains produce a 20 kDa heatlabile enterotoxin, which is a Zn+-dependent metalloprotease. This toxin is associated with diarrheal disease and active inflammatory bowel disease. Bacteroides are also more resistant to antimicrobial agents than the other anaerobes. Although only

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... rbapenems and nitroimidazoles remain highly active against B. fragilis strains, carbapenem-resistant isolates have already been reported. The aim of this study was to investigate the coexistence of enterotoxin (bft) and carbapenemase genes among B. fragilis, which were isolated from different clinical samples (n= 56) and from humans feces (n= 16). Materials and Methods: We examined a total of 72 B. fragilis isolates by polymerase chain reaction (PCR) for the presence of bft and cfiA genes using agar dilution methods recommended by the Clinical and Laboratory Standards Institute (CLSI) (M11-A7) for susceptibility of imipenem and meropenem. Results: Twenty six (36%) strains had the cfiA gene and 22 (30.5%) strains had the bft gene; 8 (11%) isolates harbored both the cfiA and bft genes. However, the coexistence of bft and cfiA genes was not statistically significant. Four strains were resistant to imipenem and 6 strains were resistant to meropenem, and all the carbapenem-resistant strains (n= 6) were cfiA-positive. Conclusion: Although our data did not reveal the coexistence of the bft and cfiA genes in B. fragilis strains, the prevalence of these two genes was higher than the data of earlier studies in the literature. According to our results, the high rate of cfiA-positive isolates in Bacteroides is worrying, and reduces the therapeutic options for treating infection caused by these organisms. Thus, it is important to monitor B. fragilis for emergence of resistant strains.