In this study, the association between antimicrobial susceptibility, PCR ribotype and presence of the ermB gene in clinical isolates of Clostridium difficile was investigated. PCR ribotyping and ermB gene PCR were performed on 131 C. difficile isolates. The susceptibility of these isolates to metronidazole, vancomycin, piperacillin/tazobactam (TZP), clindamycin, moxifloxacin and rifaximin was also determined. Use of antibiotics within the previous 2 months was documented. Resistance rates to clindamycin, moxifloxacin and rifaximin were 67.9%, 62.6% and 19.1%, respectively. No metronidazole, vancomycin or TZP resistance was detected. Previous exposure to moxifloxacin was significantly correlated with resistance to this antibiotic, but prior use of clindamycin was not significantly correlated with clindamycin resistance. Sixty-four strains (48.9%) carried the ermB gene, of which all but one (98.5%) were resistant to clindamycin. The clindamycin resistance rates of the common PCR ribotypes (018, 017 and 001) were 91.4%, 100% and 84.2%, respectively, and their moxifloxacin resistance rates were 91.4%, 95.0% and 78.9%, respectively. Resistance rates to rifaximin were 5.7% and 95.0% in ribotype 018 and 017 strains, whilst none of the 001 strains were resistant to rifaximin. In conclusion, the common ribotypes 018, 017 and 001 of C. difficile have high rates of resistance to clindamycin and moxifloxacin, but differ greatly in the frequency of rifaximin resistance.
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