An Overview of the Genetic Mechanisms of Colistin-Resistance in Bacterial Pathogens: An Indian Perspective.

Colistin resistance in bacteria is a growing global issue, given its role as a critical last-resort antibiotic, particularly for treating Gram-negative bacterial infections. Pathogens adopt multiple resistance mechanisms, mediated either by plasmids or chromosomal changes. Some of the most frequently observed strategies include the occurrence of plasmid-borne mobile colistin resistance (mcr) genes, enhanced efflux pump activity, mutations in the regulatory systems, and alterations in the lipid A structure. This article provides an overview of the studies investigating the genetic mechanisms underlying colistin resistance in nosocomial Gram-negative bacteria from India. A total of 37 studies were identified through online searches across various databases, including PubMed, ScienceDirect, and Web of Science. These studies were reviewed to examine bacterial species and their mechanisms of colistin resistance. Over 26 (70.27%) studies were focused on Klebsiella pneumoniae. The most commonly reported mechanism of colistin resistance involved mutations in the two-component systems pmrAB and phoPQ. Plasmid-mediated colistin-resistant mcr genes were identified in 22 studies (18.18%). Four studies reported the overexpression of efflux pump genes as a mechanism of colistin resistance. This article provides a comprehensive summary of these studies, emphasizing the presence of diverse resistance mechanisms across various pathogens. It underscores the necessity for future genomic research on a broader range of pathogens to investigate the prevalence of different mechanisms of colistin resistance in the various regions of India.