Abstract
Background:
Pigeons are a potential reservoir for several pathogenic microorganisms, including Escherichia coli, Salmonella spp., Chlamydia spp., and Cryptococcus spp. These microorganisms can also be pathogenic and antibiotic-resistant bacteria, posing risks to food safety and public health.

Aim:
To determine antibiotic resistance and identify the qnr (qnrA, qnrB, qnrS) and aac(6’)-ib-cr genes in quinolone-resistant E. coli strains isolated from pigeon farms in Bac Ninh, Vietnam.

Methods:
A total of 128 fresh dropping fecal samples were collected from pigeon farms in Bac Ninh, Vietnam, and transported to the laboratory for analysis within 24 h. The E. coli strains were identified using biochemical tests and Gram staining. The antibiotic susceptibility of the E. coli strains was assessed using the disc diffusion method. The PMQR genes of quinolone-resistant E. coli strains were detected using PCR.

Results:
In this study, 97/128 (75.8%) pigeon fecal samples tested positive for E. coli. The isolated strains showed the highest resistance to ampicillin at 69.1%, followed by sulfonamide and tetracycline at 64.9% and 52.6%, respectively. Gentamicin and trimethoprim/sulfamethoxazole were resistant by 45.4% and 48.5% of the isolates, respectively. Resistance of E. coli strains to norfloxacin, doxycycline, nalidixic acid, and cefotaxime ranged from 19.6% to 36.1%. Using the agar diffusion method, 11.3% of the isolated E. coli strains were suspected to be meropenem-resistant. Sixty-six (68.0%) of the 97 E. coli strains were identified as MDR. All quinolone-resistant E. coli strains carried at least one PMQR gene. Of these, the qnrS, qnrA, qnrB, and aac(6')-ib-cr genes were detected at rates of 65.6%, 56.3%, 15.6%, and 18.8%, respectively.

Conclusion:
The E. coli strains originating from pigeons in the study area showed resistance to multiple antibiotics, potentially posing a risk of spreading antibiotic-resistant bacterial strains in livestock farming.

Key words: Antibiotic resistance; PMQRs; E. coli; Pigeon; Bac Ninh.