Molecular Detection of Metallo-β-Lactamase Genes in Carbapenem-Resistant Non-Fermenting Gram-Negative Bacilli from a Tertiary Care Hospital in Lahore, Pakistan

Abstract

Objective: This study aims to identify the most common metallo-beta-lactamase (MBL) genes in non-fermenting Gram-negative bacilli (NFGNB) through both phenotypic and genotypic analysis, with the goal of informing new strategies to mitigate hospital-acquired infections.

Study type, settings & duration: This cross-sectional study was conducted at General Hospital, Lahore and Institute of Public Health, Lahore from January to December 2015.

Methodology: A total of 170 NFGNB isolates were identified and tested in this study. Antimicrobial susceptibility testing was performed using the disc diffusion technique. Isolates were analyzed for MBL production through a phenotypic method (DDST) and for the presence of MBL genes (blaIMP and blaVIM) via PCR.

Results: A total 170 out of 253 samples (67.19%) were identified as NFGNB (blood: 11.3%, pus: 16.4%, urine: 26.4%, genital: 5.6%, respiratory: 39.6%). Among the isolates, 53 (53/170: 31.17%) exhibited resistance to imipenem whereas highest resistance was found against Amikacin (96.2%). The current study revealed that 54.05% isolates of P. aeruginosa, 84.61% of A. baumannii, and 50% of P. luteola were MBL positive on DDST. On PCR 51.35% P. aeruginosa, and 38.46% A. baumannii were found positive for MBL genes (n=24) as blaIMP (14/24: 58.33%) and blaVIM (8/24: 33.33%).

Conclusion: DDST is effective for ascertaining antimicrobial susceptibility followed by PCR for the detection of MBL producers among NFGNB showing a sensitivity and specificity of 100% and 72% respectively.