Antimicrobial resistance in the Bacteroides fragilis group in faecal microbiota from healthy Danish children

•Faecal Bacteroides fragilis group isolates from healthy children were characterised.•The rate of reduced susceptibility to meropenem was 1.9% and clindamycin 21.2%.•The rate of reduced susceptibility to piperacillin/tazobactam was 5.0%.•No metronidazole-resistant isolates were found.

The Bacteroides fragilis group constitute a significant portion of the human gut microbiota and comprise a major proportion of anaerobic bacteria isolated in human infections. We established a baseline of antimicrobial susceptibility rates in the B. fragilis group in the intestinal tract of relatively antibiotic-naive healthy Danish children. From 174 faecal samples collected from children attending day care, 359 non-duplicate isolates were screened for antimicrobial susceptibility. Of these, 0.0%, 1.9%, 5.0% and 21.2% of isolates were intermediate-susceptible or resistant to metronidazole, meropenem, piperacillin/tazobactam and clindamycin, respectively. Eighteen additional studies reporting susceptibility rates in the B. fragilis group bacteria were identified by conducting a literature search. Heterogeneity among results from studies of B. fragilis group antimicrobial susceptibility rates in faecal microbiota exists.