Carriage of blaNDM-1 in Pseudomonas aeruginosa through multiple Inc type plasmids in a tertiary referral hospital of northeast India

Pseudomonas aeruginosa is known to be a predominant opportunistic pathogen and also a frequent cause of nosocomial infection in patients with compromised immune system. Treatment option becomes complicated when this type of organism harbour resistance determinants such as New Delhi metallo-β-lactamase-1 (NDM-1). The genetic vehicles carrying this gene are often responsible for their horizontal spread, dissemination and maintenance within a broad host range 1. Knowledge about transmission dynamics of bla NDM-1 is a key to succeed in the effort of infection control and slowing down the spread of multidrug resistance. This study was undertaken to characterize bla NDM-1 in clinical isolates of P. aeruginosa, their transmission dynamics and plasmid Inc types responsible for their horizontal transfer in a tertiary referral hospital of northeast India. The samples for the present study were collected from the patients who were admitted or attended Institutional Research and Ethical Committee. During this period, a total of 290 consecutive non-duplicate clinical isolates of P. aeruginosa were collected, of which 88 isolates were found to be non-susceptible to carbapenem by minimum inhibitory concentration (MIC). Isolates with MIC above 4, 1, 8 μg/ml for imipenem, meropenem, and ertapenem, respectively were selected as per CLSI (Clinical Laboratory Standards Institute) guidelines 2 and were subjected to modified Hodge test for detection of carbapenemase production 3 and further confirmed for the presence of metallo-β-lactamase by imipenem-EDTA disc diffusion test 4. PCR assay was performed to characterize the bla NDM gene as well as other metallo-β-lactamase