Global Burden of Colistin-Resistant Bacteria: Mobilized Colistin Resistance Genes Study (1980–2018)

Colistin is considered to be an antimicrobial of last-resort for the treatment of multidrug-resistant Gram-negative bacterial infections. The recent global dissemination of mobilized colistin resistance (<i>mcr</i>) genes is an urgent public health threat. An accurate estimate of the global prevalence of <i>mcr</i> genes, their reservoirs and the potential pathways for human transmission are required to implement control and prevention strategies, yet such data are lacking. Publications from four English (PubMed, Scopus, the Cochrane Database of Systematic Reviews and Web of Science) and two Chinese (CNKI and WANFANG) databases published between 18 November 2015 and 30 December 2018 were identified. In this systematic review and meta-analysis, the prevalence of <i>mcr</i> genes in bacteria isolated from humans, animals, the environment and food products were investigated. A total of 974 publications were identified. 202 observational studies were included in the systematic review and 71 in the meta-analysis. <i>mcr</i> genes were reported from 47 countries across six continents and the overall average prevalence was 4.7% (0.1-9.3%). China reported the highest number of <i>mcr</i><i>-</i>positive strains. Pathogenic <i>Escherichia coli</i> (54%), isolated from animals (52%) and harboring an IncI2 plasmid (34%) were the bacteria with highest prevalence of <i>mcr</i> genes. The estimated prevalence of <i>mcr</i><i>-1</i> pathogenic <i>E. coli</i> was higher in food-animals than in humans and food products, which suggests a role for foodborne transmission. This study provides a comprehensive assessment of prevalence of the <i>mcr</i> gene by source, organism, genotype and type of plasmid.