The occurrence of antibiotic resistance genes in drug resistant Bacteroides fragilis isolates from Groote Schuur Hospital, South Africa

• We determined the drug resistance profiles of Bacteroides fragilis clinical strains.
• TetracyclineR strains carried chromosomal tetQ, but were tigecyclineS.
• Three strains carried the cfiA gene but only two were imipenem resistant.
• One had an IS4351 promoter insertion, and the other a G to A promoter substitution.
• MetronidazoleR was not due to the nimA-J genes but to an unidentified mechanism.

Bacteroides fragilis, an anaerobic gut commensal and opportunistic pathogen, is a leading cause of anaerobic abscesses and bacteraemias. Treatment of infections is complicated by the emergence of resistance to several of the antibiotics used in the clinical setting. Genetic analysis of 23 B. fragilis isolates found that none of the metronidazole resistant strains carried the nimA-J genes, and no cfxA or ermF genes were detected. All of the tetracycline resistant isolates contained the tetQ gene and were sensitive to tigecycline. The cfiA gene was found in 3 of the strains, one of which was imipenem resistant and contained an upstream IS4351 insertion sequence. Another resistant strain had a unique G to A substitution in the promoter region of the cfiA gene, while the third was imipenem sensitive. Thirty percent of the isolates contained at least one plasmid, however, tetQ gene was located on the chromosome and not on any of the plasmids.