This study characterized the mechanisms of carbapenem resistance in gram-negative bacteria isolated from patients in Yola, Nigeria. Whole genome sequencing (WGS) was performed on 66 isolates previously identified phenotypically as carbapenem-non-susceptible. The patterns of beta-lactamase resistance genes identified were primarily species-specific. However, blaNDM-7 and blaCMY-4 were detected in all Escherichia coli and most Providencia rettgeri isolates; blaNDM-7 was also detected in 1 Enterobacter cloacae. The E. coli and E. cloacae isolates also shared blaOXA-1, while blaOXA-10 was found in all P. rettgeri, one Pseudomonas aeruginosa and 1 E. coli. Except for Stenotrophomonas maltophilia isolates, which only contained blaL1, most species carried multiple beta-lactamase genes, including those encoding extended-spectrum beta-lactamases, AmpC and OXA in addition to a carbapenemase gene. Carbapenemase genes were either class B or class D beta-lactamases. No carbapenemase gene was detected by WGS in 13.6% of isolates.
Keywords: Beta-lactamase; Carbapenem resistance; Carbapenemase.
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