Antimicrobial Resistance Profiles and Co-Existence of Multiple Antimicrobial Resistance Genes in mcr-Harbouring Colistin-Resistant Enterobacteriaceae Isolates Recovered from Poultry and Poultry Meats in Malaysia

Abstract

The co-existence of the colistin resistance (<i>mcr</i>) gene with multiple drug-resistance genes has raised concerns about the possibility of the development of pan-drug-resistant bacteria that will complicate treatment. This study aimed to investigate the antibiotic resistance profiles and co-existence of antibiotic resistance genes among the colistin-resistant <i>Enterobacteriaceae</i> isolates recovered from poultry and poultry meats. The antibiotic susceptibility to various classes of antibiotics was performed using the Kirby-Bauer disk diffusion method and selected antimicrobial resistance genes were detected using PCR in a total of 54 colistin-resistant <i>Enterobacteriaceae</i> isolates including <i>Escherichia coli</i> (<i>E</i>. <i>coli</i>) (n = 32), <i>Salmonella</i> spp. (n = 16) and <i>Klebsiella pneumoniae</i> (<i>K</i>. <i>pneumoniae</i>) (n = 6) isolates. Most of the isolates had multi-drug resistance (MDR), with antibiotic resistance against up to seven classes of antibiotics. All <i>mcr</i>-harbouring, colistin-resistant <i>Enterobacteriaceae</i> isolates showed this MDR (100%) phenotype. The <i>mcr-1</i> harbouring <i>E</i>. <i>coli</i> isolates were co-harbouring multiple antibiotic resistance genes. The seven most commonly identified resistance genes (<i>^blaTEM</i>, <i>tetA</i>, <i>floR</i>, <i>aac-3-IV</i>, <i>aadA1</i>, <i>fosA</i>, <i>aac</i>(<i>6_</i>)<i>-lb</i>) were detected in an <i>mcr-1</i>-harbouring <i>E</i>. <i>coli</i> isolate recovered from a cloacal swab. The <i>mcr-5</i> harbouring <i>Salmonella</i> spp. isolate recovered from poultry meats was positive for <i>^blaTEM</i>, <i>tetA</i>, <i>floR</i>, <i>aac-3-IV</i>, <i>fosA</i> and <i>aac</i>(<i>6_</i>)<i>-lb</i> genes. In conclusion, the colistin-resistant <i>Enterobacteriaceae</i> with <i>mcr</i> genes co-existing multiple clinically important antimicrobial resistance genes in poultry and poultry meats may cause potential future threats to infection treatment choices in humans and animals.