Colistin Resistance Mediated by Mcr-3-Related Phosphoethanolamine Transferase Genes in Aeromonas Species Isolated from Aquatic Environments in Avaga and Pakro Communities in the Eastern Region of Ghana

Abstract

Purpose Colistin is classified by the World Health Organization (WHO) as a critically important and last-resort antibiotic for the treatment of infections caused by carbapenem-resistant bacteria. However, colistin resistance mediated by chromosomal mutations or plasmid-linked mobilized colistin resistance ( mcr ) genes has emerged. Methods Thirteen mcr -positive Aeromonas species isolated from water samples collected in Eastern Ghana were analyzed using whole-genome sequencing (WGS). Antimicrobial susceptibility was tested using the broth microdilution method. Resistome analysis was performed in silico using a web-based platform. Results The minimum inhibitory concentration (MIC) of colistin for all except three isolates was >4 µg/mL. Nine new sequence types were identified and whole-genome analysis revealed that the isolates harbored genes ( mcr-3 -related genes) that code for Lipid A phosphoethanolamine transferases on their chromosomes. BLAST analysis indicated that the amino acid sequences of the mcr-3 -related genes detected varied from those previously reported and shared 79.04–99.86% nucleotide sequence identity with publicly available mcr-3 variants and mcr-3 -related phosphoethanolamine transferases. Analysis of the genetic context of mcr-3 -related genes revealed that the genetic environment surrounding mcr-3 -related genes was diverse among the different species of Aeromonas but conserved among isolates of the same species. Mcr-3 -related-gene-IS- mcr-3 -related-gene segment was identified in three Aeromonas caviae strains. Conclusion The presence of mcr-3 -related genes close to insertion elements is important for continuous monitoring to better understand how to control the mobilization and dissemination of antibiotic resistance genes.