[Plasmid-mediated colistin resistance in pathogenic bacteria]

Plasmid-mediated mcr colistin resistance has emerged as a growing global health threat by undermining one of the last therapeutic options against multidrug-resistant Gram-negative bacilli. This study provides a systematic and critical review of literature published between 2015 and 2025, including PubMed, Scopus, GenBank, and World Health Organization (WHO) reports. We analyzed the global distribution, prevalence, genetic variants, molecular mechanisms, diagnostic tools, and clinical implications of mcr. Findings reveal widespread dissemination across humans, animals, and the environment, with the highest burden in Asia and an alarming increase in Latin America. Variants such as mcr-3 and mcr-9 are particularly concerning due to their coexistence with carbapenemase genes, raising the risk of pan-resistant strains. Clinically, these infections are associated with high mortality, prolonged hospital stays, and increased costs, while asymptomatic intestinal carriage facilitates silent spread. Strengthening microbiological and genomic surveillance, implementing rapid diagnostic methods, regulating polymyxin use, and fostering novel therapeutic alternatives are urgently needed. Plasmid-mediated colistin resistance should not be seen as an isolated phenomenon but as a complex clinical, epidemiological, and social challenge requiring immediate and coordinated action to prevent a post-antibiotic era.