Background: The species of the Bacteroides fragilis group are important components of human microbiota, but as opportunistic pathogens they can be the causative agents of severe infections.
Methods: The major aims of our investigation were the evaluation of the susceptibility of 400 different Hungarian B. fragilis group isolates to 10 antibiotics by the agar dilution method, the comparison of our resistance data with previous national and international antibiotic resistance data and the comparison of present data in regional aspect. The MIC-values on 10 antibiotics of all the strains were determined with the agar dilution method by CLSI. The presence of the cfiA gene in Division II B. fragilis strains was confirmed by RT-PCR.
Results: We detected a relatively high resistance rate of ampicillin, moxifloxacin, clindamycin and tetracycline, but amoxicillin/clavulanic acid, metronidazole, tigecycline and chloramphenicol showed excellent activity. In this study, we found that 6.75% of the isolates were resistant to cefoxitin and 7% to meropenem, while 8.58% of our B. fragilis strains harboured the cfiA gene. Most of the meropenem resistant strains were isolated in one of the participating centres. In the case of meropenem, cefoxitin, clindamycin and high-level-ampicillin-resistant strains, we found significant regional differences.
Discussion: Most of the results of our study were concordant with previous national and international data, with the exception of amoxicillin/clavulanic acid, cefoxitin and meropenem.
Conclusions: Our study highlighted the importance of the periodic monitoring of the antimicrobial susceptibility of Bacteroides species providing important information for the appropriate therapy.
Keywords: Bacteroides species; agar dilution; antibiotic susceptibility test.