Molecular Detection of Colistin Resistance <i>mcr</i>-<i>1</i> Gene in Multidrug-Resistant <i>Escherichia coli</i> Isolated from Chicken

Zoonotic and antimicrobial-resistant <i>Escherichia coli</i> (hereafter, <i>E. coli</i>) is a global public health threat which can lead to detrimental effects on human health. Here, we aim to investigate the antimicrobial resistance and the presence of <i>mcr-1</i> gene in <i>E. coli</i> isolated from chicken feces. Ninety-four <i>E. coli</i> isolates were obtained from samples collected from different locations in Bangladesh, and the isolates were identified using conventional microbiological tests. Phenotypic disk diffusion tests using 20 antimicrobial agents were performed according to CLSI-EUCAST guidelines, and minimum inhibitory concentrations (MICs) were determined for a subset of samples. <i>E. coli</i> isolates showed high resistance to colistin (88.30%), ciprofloxacin (77.66%), trimethoprim/sulfamethoxazole (76.60%), tigecycline (75.53%), and enrofloxacin (71.28%). Additionally, the pathotype <i>eaeA</i> gene was confirmed in ten randomly selected <i>E. coli</i> isolates using primer-specific polymerase chain reaction (PCR). The presence of <i>mcr-1</i> gene was confirmed using PCR and sequencing analysis in six out of ten <i>E. coli</i> isolates. Furthermore, sequencing and phylogenetic analyses revealed a similarity between the catalytic domain of <i>Neisseria meningitidis</i> lipooligosaccharide phosphoethanolamine transferase A (LptA) and MCR proteins, indicating that the six tested isolates were colistin resistant. Finally, the findings of the present study showed that <i>E. coli</i> isolated from chicken harbored <i>mcr-1</i> gene, and multidrug and colistin resistance. These findings accentuate the need to implement strict measures to limit the imprudent use of antibiotics, particularly colistin, in agriculture and poultry farms.