Phenotypic and genotypic methods for detection of metallo beta lactamases among carbapenem resistant Enterobacteriaceae clinical isolates in Alexandria Main University Hospital

Dissemination of carbapenem resistant Enterobacteriaceae (CRE) poses a considerable threat to public health. The aim of the present work was to estimate the prevalence of metallo beta lactamases (MBL) among CRE isolated from Alexandria Main University Hospital, Egypt, to evaluate the performance of different phenotypic methods for the detection of MBL, and to investigate the local antimicrobial sensitivity profile of these isolates. Eighty CRE were tested for MBL production by Etest® MBL MP/MPI, EDTA double disc synergy test, and EDTA combined disc test. All isolates were confirmed as MBL producers by polymerase chain reaction (PCR). Antibiotic sensitivity testing was performed using disc diffusion method. Among the 80 CRE, 56 isolates (70%) were MBL by PCR. Fifty-four isolates were positive for NDM (96.4%). Meropenem EDTA CDT was the most sensitive test (94.6%). Blood was the most frequent sample from which MBL were isolated (51.7%). Majority of the isolates were isolated from intensive care units (82.1%). All MBL were multidrug resistant; Colistin and polymyxin B showed the lowest resistance rate (26.8 and 19.6%, respectively). The EDTA-CDT will provide a reliable, convenient, and cost-effective approach for detection of MBL in laboratories, which cannot afford to perform molecular tests. Key words: Metallo beta lactamases, carbapenem resistant Enterobacteriaceae, New Delhi lactamase.