Dissemination and spread of New Delhi metallo-beta-lactamase-1 superbugs in hospital settings

Objective: To find out frequency of isolation of carbapenem-resistant enterobacteriaceae and the predominantly responsible metallo-beta-lactamasegene in a hospital setting. Methods: The descriptive, cross-sectional study was conducted from May 2009 to June 2012 at the Aga Khan University Hospital, Karachi, and comprised non-duplicate clinical carbapenem-resistant enterobacteriaceae isolates obtained from different collection units across Pakistan. Kirby-Bauer disk diffusion screening of carbapenem-resistant enterobacteriaceae was confirmed by minimum inhibitory concentration using E-test. Polymerase chain reaction assay was performed to detect blaKPC, blaNDM-1, blaIMP, and blaVIM genes. In addition variable number tandem repeat typing was performed on selected cluster of New Delhi metallo-beta-lactamase-1positive Klebsiella pneumoniae. Results: Of the 114 carbapenem-resistant enterobacteriaceae isolates, 104(94%) tested positive for blaNDM-1 gene. At 68(66%), Klebsiella pneumoniae was the most frequent species isolated, followed by E.coli 33(31%). Moreover, 89(78%) of the blaNDM-1 gene positive Klebsiella pneumonia isolates were from the clinical samples of patients admitted to the critical care units and 75(66%) were from neonates and the elderly. Of the 65(67%) patients suffering from bacteraemia and sepsis, 32(57%) had expired, of which 22(60%) were aged <1 month. Variable number tandem repeat analysis of hospital-acquired New Delhi metallo-beta-lactamase-1-positive Klebsiella pneumoniae showed similarities between the isolates. Conclusion: New Delhi metallo-beta-lactamase-1-positive enterobacteriaceae was found widely disseminated in major hospitals across Pakistan. Patients at extreme ages and those in critical care units were found to be the most affected with fatal outcomes.