Prevalence and Genetic Analysis of -Positive Aeromonas Species from Humans, Retail Meat, and Environmental Water Samples.

The mobile colistin resistance gene is globally disseminated in both and species, with the latter potentially serving as a reservoir for this gene. Here, we investigated the prevalence of in rectal swabs from humans, in food-producing animals and their products, and in the aquatic environment, and we investigated the genetic relationships between the -positive isolates. An enriched broth screening method was used to detect in samples, and species identification of isolates from positive samples was carried out by matrix-assisted laser desorption ionization-time of flight mass spectrometry and shotgun sequencing. All -positive isolates were subjected to antimicrobial susceptibility testing, conjugation, and whole-genome sequencing. Ten isolates, including 2 from human rectal swabs, 1 from pork, 3 from chicken meat, and 4 from the aquatic environment, were positive for , but only 2 showed resistance to colistin. In addition to the variants identified previously (the novel variants were termed to ), all isolates harbored -like genes downstream of the variants. The MCR-3.13 to MCR-3.18 proteins exhibited only 89.2% to 96.1% amino acid identity to the original MCR-3 protein. Whole-genome sequence analysis indicated diversity within the genetic environments of -positive isolates and possible transmission between different sources in China and even worldwide. Close relationships between -positive and -negative isolates suggested that might be common in species, which are not inherent hosts of but may act as an important reservoir of this mobile colistin resistance gene.