en Microbiology Microbiology Original Article Original Article <span style="font-size:14px;"><span style="font-family:Times New Roman;"><em><span style="color:#0000ff;"><strong>Background: </strong></span></em>A routine phenotypic test has not been recommended for detection of metallo-&beta;-lactamases (MBLs) producing <em>Enterobacteriaceae</em> species such as <em>Escherichia coli</em>. The current study was conducted to compare the 2-Mercaptopropionic acid (2-MPA) phenotypic method and ertapenem non-susceptibility test with polymerase chain reaction in predicting the production of MBLs in clinical isolates of <em>E. coli</em>.<br> <strong><em><span style="color:#0000ff;">Methods:</span></em> </strong>Antimicrobial susceptibility test for beta-lactam antibiotics were performed by disk diffusion method. All isolates which showed inhibition zones of &le; 22 mm for CAZ and &le; 27 mm for CTX were considered potential MBLs producing isolates. The production of MBLs was confirmed using 2-MPA compound. Also, susceptibility to ertapenem was evaluated in all isolates. Conventional PCR was performed to detect <em>bla</em>IMP-1 and/or <em>bla</em>NDM-1 genes in all potential MBLs producing <em>E. coli</em> isolates.<br> <strong><em><span style="color:#0000ff;">Results:</span></em> </strong>Of 259, 138 (53.3%) isolates were potential MBLs producing bacteria. One hundred and fifteen out of 138 (83.3%) isolates were susceptible to ertapenem. MBLs production was confirmed in 75/138 (54.4%) isolates by 2-MPA phenotypic method.&nbsp; The <em>bla</em>NDM-1 or/and <em>bla</em>IMP-1 genes were found in 30/75(40%) and 39/115(33.9%) isolates which were confirmed by 2-MPA and were susceptible to ertapenem, respectively. The Sensitivity of 2-MPA method and ertapenem non-susceptibility test compared with PCR were 65.2% and 15.2%, and the specificity was 52.1% versus 82.6%, respectively.<br> <strong><em><span style="color:#0000ff;">Conclusion:</span></em> </strong>This study demonstrated that the 2-MPA phenotypic method does not have acceptable sensitivity and specificity in comparison with PCR, but its results are more reliable for the detection of MBL producing <em>E. coli</em> isolates compared with non-susceptibility to ertapenem.</span></span> 2-MPA, E. coli, Ertapenem, blaNDM-1, blaIMP-1 426 431 http://caspjim.com/browse.php?a_code=A-10-1580-1&slc_lang=en&sid=1 Zahra Shahandeh shahandehza44@gmail.com 100319475328460024946 100319475328460024946 Yes Department of Laboratory Sciences, Faculty of Paramedical Sciences, Babol University of Medical Sciences, Babol, Iran Narges Kalantari nfkala@gmail.com 100319475328460024947 100319475328460024947 No Department of Laboratory Sciences, Faculty of Paramedical Sciences, Babol University of Medical Sciences, Babol, Iran Farahnaz Sadigian f.sadigh@gmail.com 100319475328460024948 100319475328460024948 No Department of Laboratory Sciences, Faculty of Paramedical Sciences, Babol University of Medical Sciences, Babol, Iran