Plasmid-Mediated Colistin Resistance in Salmonella enterica: A Review

Colistin is widely used in food-animal production. Salmonella enterica is a zoonotic pathogen, which can pass from animal to human microbiota through the consumption of contaminated food, and cause disease, often severe, especially in young children, elderly and immunocompromised individuals. Recently, plasmid-mediated colistin resistance was recognised; mcr-like genes are being identified worldwide. Colistin is not an antibiotic used to treat Salmonella infections, but has been increasingly used as one of the last treatment options for carbapenem resistant Enterobacteria in human infections. The finding of mobilizable mcr-like genes became a global concern due to the possibility of horizontal transfer of the plasmid that often carry resistance determinants to beta-lactams and/or quinolones. An understanding of the origin and dissemination of mcr-like genes in zoonotic pathogens such as S. enterica will facilitate the management of colistin use and target interventions to prevent further spread. The main objective of this review was to collect epidemiological data about mobilized colistin resistance in S. enterica, describing the mcr variants, identified serovars, origin of the isolate, country and other resistance genes located in the same genetic platform.