Molecular detection of the New Delhi metallo-β-lactamase clinical variant with double mutation- V88L and M154L in Escherichia coli isolates from South India

Carbapenem is usually prescribed as a last resort of antibiotic for treating drug resistant Gram-negative bacterial infections. However, the rise in carbapenem resistance due to the emergence of Zn2+ dependent New Delhi metallo-β lactamase (NDM) variants imposes a huge threat to global health. In Indian context, focusing on molecular epidemiology and underpinning the genetic insights of such continuously evolving superbug is perquisite to guide any form of control strategies or therapeutic interventions. Herein, we investigated the occurrence of NDM variants in Escherichia coli (n = 70) isolated from clinical samples. PCR assay targeting blaNDM gene detected 5 E. coli isolates as NDM positive. Sequencing analyses of blaNDM region of the plasmid DNA determined two types of variants viz., NDM-1 (n = 3) and NDM-5 (n = 2). Notably, NDM-5 variants harbored V88L and M154L mutations, which are known to increase the fitness of NDM-5 variant towards host immune system and zinc starvation. On further characterization, three NDM variants showed the ESBL and AmpC β-lactamase genes, along with 3 different plasmid replicon types (L/M, Y, FIC). Virulence profiling showed traT gene as the most predominant gene among the variants. The emergence of NDM variants especially NDM-5 like variants with critical mutations in enterobacteriaceae increases the significant menaces to the global healthcare. The fact that these NDM variants harboring other antibiotic resistance markers, along with plasmid replicons and virulence genes can be transmitted underlines the gravity of this public health issue.