Antibiotics have been widely used in animal husbandry to promote growth and treat infectious diseases. However, their extensive use can lead to significant consequences, including disruption of the gut microbiota in treated animals and the emergence of antibiotic-resistant bacteria. Additionally, antibiotics and their metabolites may enter the environment through animal manure, contributing to the spread of antibiotic resistance genes among bacterial populations.

This study aimed to assess the prevalence of colistin-resistant Escherichia coli in chicken meat, chicken manure, and surface samples (i.e., poultry drinkers). Samples were collected over a one-month period. Colistin-resistant bacteria were isolated using a growth medium supplemented with colistin sulfate. A total of 81 samples were analyzed, of which 90% were positive for the presence of colistin-resistant strains, including coliforms and Pseudomonas spp.

Based on morphological characteristics, 31 Escherichia coli isolates were selected for confirmation of the mcr-1 gene using qPCR technique. Subsequently, antimicrobial susceptibility of the selected bacteria was determined by the Kirby-Bauer disk diffusion method with the following antibiotics: colistin, imipenem, ertapenem, meropenem, ceftazidime, cefotaxime, cefepime, and ciprofloxacin. The minimum inhibitory concentration (MIC) for colistin was evaluated using both ETEST and broth microdilution methods.

Overall, one Escherichia coli strain was positive for the presence of of mcr-1 gene. Nonetheless, several isolates showed intermediate susceptibility or resistance to multiple antibiotics including cephalosporins and fluoroquinolones.