The occurrence and molecular detection of mcr-1 and mcr-5 genes in Enterobacteriaceae isolated from poultry and poultry meats in Malaysia

Abstract

The advent of antimicrobials-resistant (AMR), including colistin-resistant bacteria, poses a significant challenge to animal and human health, food safety, socio-economic growth, and the global environment. This study aimed to ascertain the colistin resistance prevalence and molecular mechanisms of colistin resistance in <i>Enterobacteriaceae</i>. The colistin resistance was determined using broth microdilution assay, PCR; and Sanger sequencing of <i>mcr</i> genes responsible for colistin resistance in <i>Enterobacteriaceae</i> (<i>n</i> = 627), including <i>Escherichia coli</i> (436)<i>, Salmonella</i> spp. (<i>n</i> = 140), and <i>Klebsiella pneumoniae</i> (<i>n</i> = 51), obtained from chicken and chicken meats. Out of 627 <i>Enterobacteriaceae</i>, 8.6% of isolates exhibited colistin resistance phenotypically. Among these colistin resistant isolates, 9.3% (<i>n</i> = 37) were isolated from chicken meat, 7.2% (<i>n</i> = 11) from the cloacal swab of chicken and 7.9% (<i>n</i> = 6) from the litter samples. Overall, 12.96% of colistin-resistant isolates were positive with <i>mcr</i> genes, in which <i>mcr-1</i> and <i>mcr-5</i> genes were determined in 11.11% and 1.85% of colistin-resistant isolates, respectively. The <i>E. coli</i> isolates obtained from chicken meats, cloacal swabs and litter samples were found positive for <i>mcr-1</i>, and <i>Salmonella</i> spp. originated from the chicken meat sample was observed with <i>mcr-5</i>, whereas no <i>mcr</i> genes were observed in <i>K. pneumoniae</i> strains isolated from any of the collected samples. The other colistin resistance genes, including <i>mcr-2, mcr-3, mcr-4, mcr-6, mcr-7, mcr-8, mcr-9,</i> and <i>mcr-10</i> were not detected in the studied samples. The <i>mcr-1</i> and <i>mcr-5</i> genes were sequenced and found to be 100% identical to the <i>mcr-1</i> and <i>mcr-5</i> gene sequences available in the NCBI database. This is the first report of colistin resistance <i>mcr-5</i> gene in Malaysia which could portend the emergence of <i>mcr-5</i> harboring bacterial strains for infection. Further studies are needed to characterize the <i>mr-5</i> harbouring bacteria for the determination of plasmid associated with <i>mcr-5</i> gene.