Prevalence and antibiotic susceptibility of Bacteroides fragilis group isolated from stool samples in North Lebanon

Fifty one strains of the Bacteroides fragilis group were isolated from 45 fecal samples. Classical phenotypic identification showed that 16 isolates were B. thetaiotaomicron, 12 B. uniformis, 9 B. eggerthii, 7 B. vulgatus, 3 B. caccae, 2 Parabacteroides distasonis with 1 identified B. ovatus and 1 B. fragilis. The 51 strains were tested for susceptibility against 16 antimicrobial agents and the MICs for metronidazole were determined. The tests showed that imipenem, meropenem and chloramphenicol were the most effective antibiotics (98%, 98% and 92.16% of susceptibility, respectively) followed by ticarcillin/clavulanic acid, piperacillin/tazobactam, rifampin (88.24% susceptibility), moxifloxacin 86.27% and tigecycline 84.31%. Ofloxacin and cefotaxime were the least effective antibiotics with 27.45% and 0% of activity respectively. Only six of the 51 isolated strains were resistant to metronidazole with MICs = 64 mg/L (1 strain) and > 256 mg/L (5 strains).