Detection of New Delhi Metallo-Beta-Lactamase-1 (NDM-1) in carbapenem-resistant Klebsiella pneumoniae isolated from a university hospital in Iran

Abstract

Background: New Delhi metallo-beta-lactamase-1(NDM-1) is a novel type of metallo-beta-lactamase (MBL) which inactivates all beta-lactam antibiotics except aztreonam. Enterobacteriaceae expressing NDM-1 have been identified worldwide. The aim of this study was to detect MBLs in carbapenem-resistant K. pneumoniae isolates obtained from patients hospitalized in one of the university hospitals in Isfahan, Iran. Methods: Of the 112 isolates obtained from various clinical samples, 49 were selected for carbapenemase detection based on their reduced susceptibility to imipenem or meropenem according to the disc diffusion method. These isolates were screened for carbapenemase and MBL production using the Modified Hodge Test (MHT) and Epsilometer test (E-test) MBL strips. Polymerase chain reaction was performed on all 49 isolates using specific primers to detect genes encoding IMP (active on imipenem), VIM (Verona integron-encoded metallo-beta-lactamase), SPM-1 (Sao Paulo metallo-beta-lactamase) and NDM-1. Results: Among 49 carbapenem-resistant isolates, 32 (65.3 ) were positive for MHT and 6 (12.2 ) were found positive for blaNDM-1. Other MBL genes were not detected. Conclusion: This is the second report on the detection of blaNDM-1 in Iran since it was first reported by Shahcheraghi and colleagues in 2012. This study indicated that resistance to carbapenems and isolation of bacteria producing NDM-1 is increasing. Therefore, the rapid detection of isolates expressing NDM-1 is essential to control their spread.