Prevalence of metallo-β-lactamase NDM-1-producing multi-drug resistant bacteria at two Pakistani hospitals and implications for public health

SummaryBackgroundThe rapid spread of metallo-β-lactamase producing clinical pathogens is a matter of great concern and with the addition of NDM-1 it poses more threat for public health as NDM-1 positive isolates show resistance to most of the antibiotics. The current study was carried out to determine the prevalence of extended-spectrum β-lactamases (ESBLs) and metallo-β-lactamases (MBLs), particularly NDM-1 in clinical multi-drug resistant isolates from two tertiary care hospitals in Pakistan.MethodsA total of 356 clinical isolates were included in the study where 301 isolates were collected from the Pakistan Institute of Medical Sciences (PIMS), Islamabad and 55 were collected from the Mayo Hospital Lahore. The isolates were screened for ESBLs and MBLs production by phenotypic method and PCR was performed to detect the presence of blaVIM, blaIMP and blaNDM-1 genes.ResultsOut of 356 clinical isolates, 160 showed carbapenem resistance. Of these 160 isolates, 131 displayed MBLs production as accessed by combined disk method. In MBLs producing organisms, PCR amplification confirmed 31 (23.6%) isolates harboring blaNDM-1 gene, 33 (25.1%) isolates having blaVIM gene and 2 (1.5%) isolates displaying blaIMP gene. Plasmid profile analysis of NDM-1 positive organisms showed variable number of plasmids which were stable during serial passages in antibiotic free media. The prevalence of ESBL producing organisms was recorded to be 87.5%.ConclusionThe results show a high level of NDM-1 positive organisms from variety of samples at both hospitals, implicating the spread of MBL genes in clinical isolates