Comparative Study of Phenotypic Detection Methods of Metallo-beta-lactamase (MβL) Among Carbapenem Resistant Gram-Negative Bacilli (GNB) Isolated from Intensive Care Units (IUC) Patients

Abstract

Background: Metallo-beta-lactamase (MβL) mediated resistance is an emergency threat in health care settings, and its identification is essential for treatment and infection control. Objectives: this study aimed to detect the MβL prevalence in Gram negative bacilli (GNB) and to compare its phenotypic detection methods. Methodology: Ninety six (96) isolates of GNB were isolated from different clinical specimens collected from patients admitted to intensive care units (ICU) of Ain Shams Hospitals, from February 2018 to June 2018. Isolates were screened for carbapenem resistance with imipenem 10 µg and meropenem 10 µg discs. The resistant isolates were tested for antibiotic susceptibility by disc diffusion method, and Meropenem minimum inhibitory concentration (MIC) were determinated, then the production of MβL was detected by imipenem-ethylene diamine tetra-acetic acid (EDTA) combined disc test (IPM-EDTA CDT), ceftazidime -EDTA combined disc test (CAZ-EDTA CDT) and Imipenem - EDTA double disc synergy test (IPM-EDTA DDST).Results: Forty three (43) isolates (44.7%) were resistant to carbapenem. Klebsiella pneumoniae (K.pneumoniae) was the most common isolated species; 29 (67.4%) isolates. Forty (40) isolates (93%) were positive for MβL by IPM-EDTA CDT method, whereas 36 (83.7%) were positive by CAZ -EDTA CDT method and 19 isolates (44.2%) were positive for MβL by IPM-EDTA DDST. Conclusion: High prevalence of MβL was detected among our isolates and IMP-EDTA CDT can be used as a phenotypic test in detection of MβL production.