Investigation of NDM metallo-beta-lactamase and CMY-2 AmpC β-lactamase production in Escherichia coli and Enterobacter spp. isolated from human

Abstract

New Delhi metallo-beta-lactamase (NDM) and CMY-2-AmpC β-lactamase are among the most important resistance factors against carbapenem and beta-lactam antibiotics. Considering the few studies in Iran, here NDM and CMY-2 production in Escherichia coli (E.coli) and Enterobacter isolates were evaluated. Acquired resistance profiles of isolates were determined based on the new definitions as multi-drug resistant (MDR), extensively drug-resistant (XDR) and pan-drug resistant (PDR). In carbapenem-resistant strains, minimum inhibitory concentration (MIC) of different antibiotics by Etest method and the clonal relationship using enterobacterial repetitive intergenic consensus (ERIC)-PCR were determined. The frequency of blaNDM and blaCMY-2 was examined using phenotypic methods and PCR. Among 466 E.coli and 135 Enterobacter isolates, 42 and 28 different resistotypes were observed, respectively. In E.coli strains, 88 and 0.2 of isolates were MDR and XDR, respectively and these percentages in Enterobacter strains were 91.9 and 1.5 but no PDR strain was detected. The most efficient antibiotics were tigecycline, colistin, carbapenems, chloramphenicol, minocycline, fosfomycin, piperacillin/tazobactam, and amikacin. In addition, 9 (1.9) of E.coli and 9 (6.7) of Enterobacter isolates were non-susceptible to carbapenems. The 6 E.coli and 2 Enterobacter strains were positive for AmpC by phenotypic test but blaCMY-2 gene wasn’t detected. The blaNDM-1 gene was detected in two strains (one E.coli and one Enterobacter hormaechei). ERIC-PCR results showed four main clusters in carbapenem non-sensitive isolates which two blaNDM-1 positive strains were in the distinct cluster. Results of MIC showed maximum resistance rates for beta-lactam antibiotics. © 2018, Springer-Verlag London Ltd., part of Springer Nature.