Plasmid

Antibiotics

Escherichia coli

Biology

Microbiology

Gene

Replicon

MCR-1

Enterobacteriaceae

Colistin

Genetics

Scientific Reports

The emergence and spread of mobilized colistin resistance ( mcr ) genes have triggered extensive concerns worldwide. Here, we characterized the global distribution of mcr-9 , a newly-identified variant of mcr , by assembling the data set of mcr-9 -positive isolates from GenBank database and the literature available. Genetic features of all the mcr-9 -harboring plasmids were determined by bioinformatic analysis. We showed that mcr-9 is globally distributed in 21 countries across six continents, with a wide dissemination among various species of Enterobacteriaceae strains from human, animal, food and environment. IncHI2-ST1 plasmids were found to be the predominant replicon type carrying mcr-9 . Comparative genomics highlighted that IncHI2-type plasmids may also serve as a critical reservoir of mcr-9 , from which different types of circulating plasmids acquired the mcr-9 . Results revealed that the rcnR-rcnA-pcoE-pcoS-IS 903 -mcr-9 - wbuC structure was consistent in most mcr-9 cassettes, suggesting a relatively unitary model involved in the mobilization of mcr-9 . It is most likely that the spread of mcr-9 was mainly attributed to the conjugation and recombination events of mcr-9 -carrying plasmids. In summary, our results provide a comprehensive picture of the distribution and genetic environment of mcr-9 , and demonstrate the central roles played by IncHI2 plasmids in the worldwide dissemination of mcr-9 .

Characterization of the global distribution and diversified plasmid reservoirs of the colistin resistance gene mcr-9