Detection of <i>bla</i>NDM-1 and Genetic Relatedness in Clinical Isolates of <i>Escherichia coli</i> Producing Extended Spectrum <i>β</i>-Lactamase from Tertiary Care Centres in South India

Abstract

Background: Extended spectrum β -lactamases (ESBL) producing E. coli co-producing other β -lactamases and exhibiting co-resistance to different antibiotic classes continue to emerge as a threat to clinical field. This study aimed to analyze the co-production of New Delhi metallo- β -lactamase-1 ( bla NDM-1) in ESBL producing plasmid-bearing clinical isolates collected from two tertiary care centres in Kerala, South India, and to understand their genetic relatedness. Methods: Antibiotic resistance phenotypes of 44 clinical isolates were determined by disc-diffusion method. Plasmid-bearing isolates, detected by the alkaline-lysis method, which also tested positive for ESBL production, were screened for the presence of bla NDM-1 by polymerase chain reaction. Plasmid, random amplified polymorphic DNA profiles and bla NDM-1 sequence-based phylogenetic tree were analyzed to understand the genotypic similarities among the isolates. Results: Beta-lactam antibiotics, quinolones, cephalosporins, used in this study, and AZM were found to be ineffective against the isolates as significantly high number of isolates were resistant to these antibiotics (P < 0.01). Plasmid bearing isolates constituted 57% (n = 25), all of which were found to be ESBL producers. bla NDM-1 amplicons were noticed in four (16%) isolates and these DNA sequences showed homology between them and with similar sequences reported from other countries like Japan and Korea. Plasmid and RAPD profiles demonstrated that most of the isolates, including those harbouring bla NDM-1 shared genetic similarities as well as an apparent geographical distinctiveness. Conclusion: The predominance of ESBL production and the occurrence of bla NDM-1 in plasmid-bearing isolates observed in our study corroborate the worldwide drug-resistance scenario. This study thus warrants the need for constant surveillance in the face of sparse information available in Kerala State on the emerging drug resistance in clinical bacteria.