Multidrug Antimicrobial Resistance and Molecular Detection of mcr-1 Gene in Salmonella Species Isolated from Chicken.

Abstract

Simple SummaryColistin is a widely used antibiotic against infections caused by extensively drug-resistant Gram-negative bacteria. It is critical to track and monitor the presence of mcr-like genes and colistin resistance to protect a last resort treatment against highly antibiotic-resistant bacteria. In the present study, the colistin resistance gene mcr-1 was investigated, and its in-silico functional analysis in Salmonella isolates was determined. Out of 100 chicken samples (liver and intestine), 82 Salmonella spp. were isolated and characterized. Antimicrobial sensitivity was determined using different antimicrobial agents. The isolates were characterized using PCR targeting genus-specific invA and mcr-1 genes followed by in-silico functional analysis. The majority of isolates (92.68%) was found highly resistant to colistin, which demonstrated the occurrence of the colistin resistance mcr-1 gene in Salmonella isolates of chicken origin in Bangladesh. The study also showed the in-silico functional analysis and phylogenetic relationship of the colistin resistance mcr-1 gene among Salmonella isolates. The findings of the present study highlight the increasing issue of transferable colistin resistance and call for immediate action and measures to review the imprudent use of colistin in poultry production systems in Bangladesh.Colistin (polymyxin E) is widely used in animal and human medicine and is increasingly used as one of the last-resort antibiotics against Gram-negative bacilli. Due to the increased use of colistin in treating infections caused by multidrug-resistant Gram-negative bacteria, resistance to this antibiotic ought to be monitored. The study was undertaken to elucidate the molecular mechanisms, genetic relationships and phenotype correlations of colistin-resistant isolates. Here, we report the detection of the mcr-1 gene in chicken-associated Salmonella isolates in Bangladesh and its in-silico functional analysis. Out of 100 samples, 82 Salmonella spp. were isolated from chicken specimens (liver, intestine). Phenotypic disc diffusion and minimum inhibitory concentration (MIC) assay using different antimicrobial agents were performed. Salmonella isolates were characterized using PCR methods targeting genus-specific invA and mcr-1 genes with validation for the functional analysis. The majority of the tested Salmonella isolates were found resistant to colistin (92.68%), ciprofloxacin (73.17%), tigecycline (62.20%) and trimethoprim/sulfamethoxazole (60.98%). When screened using PCR, five out of ten Salmonella isolates were found to carry the mcr-1 gene. One isolate was confirmed for Salmonella enterica subsp. enterica serovar Enteritidis, and other four isolates were confirmed for Salmonella enterica subsp. enterica serovar Typhimurium. Sequencing and phylogenetic analysis revealed a divergent evolutionary relationship between the catalytic domain of Neisseria meningitidis lipooligosaccharide phosphoethanolamine transferase A (LptA) and MCR proteins, rendering them resistant to colistin. Three-dimensional homology structural analysis of MCR-1 proteins and molecular docking interactions suggested that MCR-1 and LptA share a similar substrate binding cavity, which could be validated for the functional analysis. The comprehensive molecular and in-silico analyses of the colistin resistance mcr-1 gene of Salmonella spp. of chicken origin in the present study highlight the importance of continued monitoring and surveillance for antimicrobial resistance among pathogens in food chain animals.