Carbapenemase-Producing Enterobacteriaceae Isolates from Edo State, Nigeria

The emergence and spread of carbapenem-resistant Enterobacteriaceae (CRE) are a global health problem that is of great concern to public health services (1, 2). The purpose of this study was to determine the frequency of CRE in three Nigerian hospitals and to characterize the resistance mechanisms of such isolates. A total of 218 consecutive clinical isolates of Enterobacteriaceae based on inclusion criteria were collected from March to May 2015 at three medical microbiology laboratories of hospitals in Edo State, Nigeria (see Table S1 in the supplemental material). Screening for carbapenem resistance was performed using meropenem and ertapenem discs (10 g; Oxoid, United Kingdom) according to EUCAST guidelines (3). The KirbyBauer susceptibility testing technique (4) and Etest method were carried out, and results were interpreted using EUCAST criteria (5). Identification of the involved resistance mechanisms was determined by whole-genome sequencing (WGS). Out of 218 consecutive clinical Enterobacteriaceae isolates, 9 (4.1%) were further investigated due to cutoff values above the EUCAST screening recommendations (Table 1). All isolates showed resistance to piperacillin-tazobactam and amoxicillin-clavulanic acid, all but isolate Ec4349 showed resistance to fluoroquinolones and cefotaxime, and all but two isolates each showed resistance to ceftazidime (Ec4349 and Ecl2840_1) and ertapenem (Ec4349 and Ecl10_14_15). Only Ec4349, Ecl2845, Ecl2840_1, and EclQ9 were sensitive to cefepime and aztreonam. The carbapenemase inactivation method (6) revealed positive results for all nine CRE isolates. By application of WGS, one Klebsiella pneumoniae isolate harbored the blaOXA-181 gene; two K. pneumoniae isolates harbored the blaNDM-1 gene. The blaOXA-48 gene was detected in one Escherichia coli isolate, one K. pneumoniae isolate, and four Enterobacter cloacae isolates, respectively. All isolates had a single carbapenemase resistance gene on their draft genome fragment. Thirteen plasmid incompatibility groups were identified among the nine CRE isolates. Multilocus sequence typing (MLST) grouped the nine isolates into five sequence types. Previous reports from Nigeria on molecular characterization of carbapenem resistance genes have identified genes such as blaVIM, blaGES, blaNDM, blaOXA-181, and blaKPC (7–10). blaOXA-48, obtained from our study, has only been determined phenotypically. To the best of our knowledge, our findings, where six out of nine carbapenemaseproducing isolates harbored the blaOXA-48 gene, represent the first molecular determination of the blaOXA-48 gene for Nigeria. The presence of different plasmid replicon types in carbapenemase-producing Enterobacteriaceae (CPE) underlines their importance in the dissemination of resistance genes. The IncL/M plasmid type was found in all of our OXA-48-producing isolates, correlating with previous reports indicating that Accepted manuscript posted online 12 June 2017 Citation Jesumirhewe C, Springer B, Lepuschitz S, Allerberger F, Ruppitsch W. 2017. Carbapenemase-producing Enterobacteriaceae isolates from Edo State, Nigeria. Antimicrob Agents Chemother 61:e00255-17. https://doi . org/10.1128/AAC.00255-17. Copyright © 2017 Jesumirhewe et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license. Address correspondence to Christiana Jesumirhewe, ebarunosen2002@yahoo.co.uk. LETTER TO THE EDITOR