High prevalence of NDM metallo-β-lactamase among ESBL-producing Escherichia coli İsolates

Resistance to β-lactams in Enterobacteriaceae has been increasing worldwide. This study aimed to determine the frequency of β-lactamase genes and antibiotic resistance rates of 140 extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolates obtained from urinary tract infection in Ordu Province, Turkey. Isolates were identified by classic methods and by automated system. ESBL production was confirmed by double disk synergy test and antimicrobial susceptibility was investigated by disk diffusion method. All isolates were screened for β-lactamase coding genes from three groups (A, B, and D) by polymerase chain reaction. The highest rate of susceptible isolates was observed for imipenem (IPM, 99.3%) and ertapenem (ETP, 97.9%), and the highest rate of resistant isolates was observed for cefuroxime (97.9%), ceftriaxone (97.2%), and cefazolin (90.7%). In our study, blaCTX-M1-like group was the most prevalent β-lactamase (n = 109), followed by blaTEM (n = 68), blaCTX-M2 (n = 22), and blaSHV (n = 2). By contrast to low resistance rate to IPM and ETP, we determined blaNDM in 31 isolates (22.1%). In co-prevalence of blaNDM-1 and ESBL-coding genes, a low carbapenem resistance was determined. We can confirm that blaCTX-M1-types are still the most frequent β-lactamase coding gene in Turkey. Our study showed the highest prevalence of blaNDM-1 metallo-β-lactamase coding gene in ESBL-producing E. coli