Emergence of bla CTX-M-15, qnrB1 and aac(6′)-ib-cr resistance genes in Pantoea agglomerans and enterobacter cloacae from Nigeria (sub-Saharan Africa)

Abstract

Besides hyper-production of chromosomal AmpC β-lactamases, the expression of plasmid-encoded extended-spectrum β-lactamases (ESBL) in Enterobacter spp has increased in recent years. In this study, we characterized 10 clinical isolates of Enterobacter spp and 1 isolate of Pantoea agglomerans, with respect to the occurrence of ESBL- and plasmid-mediated quinolone resistance (PQMR) genes. Species identification and antimicrobial susceptibility testing were performed by the Vitek 2 system, broth microdilution, agar diffusion and Etests methods. ESBL-, PQMR- and other resistance genes were detected using PCR and sequencing. Strain typing was done by ERIC-2 PCR. The P. agglomerans and an Enterobacter cloacae isolate were found to harbour ESBL gene blaCTX-M-15, PQMR genes qnrB and aac-(6′)-Ib-cr, trimethoprim/sulfamethoxazole resistance genes dfrA14/Sul1 and tetracycline resistance genes (tet). In addition, class 1 and 2 integrons were found in these 2 isolates. The result of the ERIC-2 PCR showed distinct patterns indicating heterogeneity of all 10 isolates. This report is the first description of CTX-M-15 production and the emergence of PMQR in P. agglomerans and E. cloacae isolates from Nigeria. Transfer of resistance genes by conjugation and the presence of mobile elements demonstrate the risk of further dissemination into other Enterobacteriaceae which may result in limited treatment options.