Metronidazole- and Carbapenem-Resistant Bacteroides

Emerging antimicrobial resistance in members of the Bacteroides fragilis group is a concern in clinical medicine. Although met-ronidazole and carbapenem resistance have been reported in Bacteroides thetaiotaomicron, a member of the B. fragilis group, they have not, to the best of our knowledge, been reported together in the same B. thetaiotaomicron isolate. Herein, we report isolation of piperacillin-tazobactam-, metronidazole-, clindamycin-, ertapenem-, and meropenem-resistant B. thetaiotaomicron from a patient with postoperative intra-abdominal abscess and empyema.Whole-genome sequencing demonstrated the pres-ence of nimDwith at least a portion of IS1169 upstream, a second putative nim gene, two-lactamase genes (one of which has not been previously reported), two tetX genes, tetQ, ermF, two cat genes, and a number of efflux pumps. This report highlights emerging antimicrobial resistance in B. thetaiotaomicron and the importance of identification and antimicrobial susceptibility testing of selected anaerobic bacteria. Increasing antimicrobial resistance has been reported in mem-bers of the Bacteroides fragilis group. Carbapenem resistance is rare and has been associated with expression of a metallo--lac-tamase encoded by cfiA, although other mechanisms have been reported. Metronidazole resistance is also rare, and though its mechanisms are incompletely delineated, it has been associated with plasmid-borne and chromosomal nim genes as well as efflu