RESUMO
OBJECTIVES: The purpose of this study was to determine the prevalence of colistin-resistant Escherichia coli carrying mcr-1, and to identify risk factors associated with mcr gene-mediated resistance. METHODS: In total, 385 cloacal samples were collected from 125 broiler farms and a questionnaire containing information about each farm was designed and filled. RESULTS: Most of the antibiotics used in the disk diffusion method were highly resistant in all samples, with tetracycline and penicillin showing 100% and 99.7% resistance, respectively. Additionally, avian pathogenic E. coli (APEC) virulence genes frequency and percentage of APEC were identified, including sitA,iucC, and astA at 77%, 70.5%, and 62% respectively. In total, 214 of 360 isolates were positive for APEC (59.4%). Based on the minimum inhibitory (MIC) test, 58% of the isolates (n = 209 of 360) were resistant to colistin, with 39.7% displaying the mcr-1 gene. The statistical analysis of risk factors that influence colistin resistance prevalence revealed several significant factors, including commercial feed, farm management, sanitization, and antibiotic use. Irregular health checks for workers, non-dipping of feet before entering poultry houses, and the use of commercial poultry feeds all contributed to higher levels of colistin resistance as measured by MIC. On the other hand, doxycycline and commercial feed was 4 and 3.2 times more likely to occur based on the final logistic model of the mcr-1 gene, respectively. CONCLUSION: Our results suggest that better biosecurity protocols should be implemented in poultry farms to reduce antibiotic-resistant bacteria. Additionally, antibiotics should be carefully monitored and used only when necessary.