Emergence of mcr-1 Gene in Colistin-Resistant Escherichia coli Isolates from Chicken in Chitwan, Nepal

Area of Science:

• Veterinary Microbiology
• Food Safety
• Antimicrobial Resistance

Background:

• Colistin resistance in *Escherichia coli* (*E. coli*) from poultry is a significant global health concern.
• The *mcr-1* gene confers resistance to colistin, a critical last-resort antibiotic.
• Poultry serves as a potential reservoir for the transmission of resistant bacteria to humans.

Purpose of the Study:

• To determine the prevalence of the *mcr-1* gene in colistin-resistant *E. coli* isolated from poultry meat in Nepal.
• To assess the antibiotic resistance patterns of *E. coli* isolates from chicken samples.
• To evaluate the potential public health implications of *mcr-1* gene dissemination in poultry.

Main Methods:

• A cross-sectional study was conducted on 210 chicken meat samples (liver, heart, spleen).
• *E. coli* isolation and identification were performed using conventional cultural methods.
• Antibiotic resistance profiling utilized the Kirby-Bauer disc diffusion method, and *mcr-1* gene detection was done via conventional polymerase chain reaction (PCR).

Main Results:

• The prevalence of *E. coli* in chicken meat samples was 39.52%, with liver having the highest isolation rate (45.45%).
• Of the *E. coli* isolates, 20.48% were resistant to colistin, and 64.70% of these harbored the *mcr-1* gene.
• Cefepime demonstrated the highest efficacy among tested antibiotics, while 54.21% of isolates were multidrug-resistant.

Conclusions:

• The high prevalence of colistin-resistant *E. coli* and the *mcr-1* gene in poultry meat indicates a substantial risk.
• Horizontal gene transfer of *mcr-1* from poultry to human pathogens is a plausible pathway for increased colistin resistance in humans.
• Urgent surveillance and control measures are necessary to mitigate the spread of colistin resistance originating from the poultry sector.