Global distribution of mcr gene variants in 214,095 metagenomic samples

Abstract Since the initial discovery of a mobilized colistin resistance gene (mcr-1), several other variants have been reported, some of which might have circulated a while before being discovered. Metagenomic data provides an opportunity to re-analyze available older data to understand the evolutionary history of recently discovered antimicrobial resistance genes (ARGs). Here, we present a large-scale metagenomic study of 442 Tbp of sequencing reads from 214,095 samples to identify the host and geographical distribution and genomic context of nine mcr gene variants (mcr-1 to mcr-9). Our results show that the dissemination of each variant is not uniform. Instead, the source and location play a role in the spread. Despite the very diverse distribution, the genomic background of the mcr genes remains unchanged as the same mobile genetic elements and plasmid replicons occur. This work emphasizes the importance of sharing genomic data for surveillance of ARGs in our fight against antimicrobial resistance.