Detection of integron-associated gene cassettes and other antimicrobial resistance genes in enterotoxigenic Bacteroides fragilis

• Multidrug resistant enterotoxigenic Bacteroides fragilis (ETBF) were identified.
• Several antimicrobial genes encoding for resistance have been detected.
• Identification of integrons in ETBF is a novel finding.
• Expression of resistance was not always associated with the presence of gene markers.

Twenty seven Enterotoxigenic Bacteroides fragilis (ETBF) strains isolated from children in Kolkata, India, were tested for their antimicrobial resistance, presence of integrons and resistance encoding genes. Almost all the strains (>90%) were resistant to two or more antimicrobials. About 59–92% of the strains were resistant to ampicillin, amoxicillin, streptomycin, tetracycline, ciprofloxacin and norfloxacin. Most of these antimicrobial agents have been used in the treatment of diarrhea and other infectious diseases. In addition, about half a number of strains (48–55%) were resistant to clindamycin, cefotaxime, ceftazidime, ampicillin/sulbactam and trimethoprim/sulfamethoxazole. Moxifloxacin and metronidazole resistance ranged from 30 to 40%. All strains however, were found to be susceptible to chloramphenicol and imipenem. Class 1 integrase (intI1) was detected in seven and class 2 integrase (intI2) in one of the twenty seven ETBF strains. Resistance gene cassettes carried by these integrons had different alleles of dfr or aad genes. Beside these integron-borne genes, other genes encoding different antimicrobial resistance were also detected. Resistance genes such as cep(A) and tet(Q) were detected in most of the ETBF strains. To the best of our knowledge, this work constituted the first extensive report from India on the detection of integrons and antimicrobial resistance genes in ETBF.