Prevalence and Characterization of nim Genes of Bacteroides spp. Isolated in Hungary

Members of the Bacteroides spp. are the anaerobic pathogens most commonly isolated from human clinical material. Metronidazole has been the drug of choice for the prevention and treatment of Bacteroides and other such anaerobic infections for nearly 40 years. Although the emergence of metronidazole-resistance in Bacteroides spp. was reported recently, the published rate remains low, at <5%. Isolates of Bacteroides spp. originating from different wards at the University Hospital of Szeged in Hungary were investigated for metronidazole resistance genes by PCR and characterized by other molecular methods. We report here the first strains of Bacteroides spp. with elevated MICs to metronidazole from Hungary. Of 167 isolates, four had metronidazole MICs >2 μg/mL, and two were positive fornim genes with metronidazole MICs of 4 and 12 μg/mL. The nim genes were determined to be nim A and nim B, and proved to be activated by upstream copies of the IS1186 element. The nim A gene was localized in a pIP417-like plasmid, and the nim B gene on the chromosome.