Analysis of mcr family of colistin resistance genes in Gram-negative isolates from a tertiary care hospital in India.

This article focuses on the prevalence and mechanisms of colistin resistance among multidrug-resistant (MDR) Gram-negative bacteria isolated from clinical specimens at a tertiary care center in Chennai, India. Among 913 isolates, predominantly Klebsiella pneumoniae, 13.8% exhibited colistin resistance, with only 1.58% harboring the plasmid-mediated mcr-5 gene detected by PCR; however, subsequent Sanger sequencing and phenotypic tests did not confirm functional mcr-5 presence. The study highlights limitations of PCR-based mcr gene screening alone and underscores the need for multiple diagnostic approaches to accurately identify colistin resistance mechanisms. It also emphasizes the clinical challenge posed by rising colistin resistance, especially in carbapenemase-producing Enterobacterales, and calls for further research to clarify resistance pathways and improve detection methods.