The characterization and correlation between the phenotypic and genotypic resistance of Campylobacter spp. isolates from commercial broilers and native chickens in the south of Thailand

ABSTRACT

Chicken is a major reservoir and source of human infections from zoonotic Campylobacter. In southern Thailand, chicken is the most popular meat consumed; however, little is known about the antimicrobial resistance (AMR) of Campylobacter spp. in chicken production systems. We aimed to investigate the prevalence and characteristics of AMR in Campylobacter isolates from commercial broiler and native chicken farms in southern Thailand. A total of 286 Campylobacter isolates (adjusted prevalence: 60.3%, SE ± 0.01) were recovered, of which 268 were identified as Campylobacter jejuni and 18 as Campylobacter coli. The adjusted prevalence of resistance was highest for nalidixic acid (98.6%), followed by ciprofloxacin (97.2%), enrofloxacin (96.4%), tetracycline (74.6%), tylosin (38.3%), and erythromycin (10.6%). Commercial broilers had resistance levels 7–11% higher to quinolones and 35–47% lower to macrolides and tetracycline (all P ≤ 0.025) compared to native chickens. Genotypic resistance analyses revealed high prevalence rates (>86%) for gyrA mutant, efflux pump CmeABC, and point mutation A2075G in the 23S rRNA gene. High homogeneity was observed among isolates within study farms. Commercial broilers exhibited higher homogeneity in AMR patterns than native chickens. The best agreement was observed between tetracycline resistance and tet(O) genes (Kappa: k = 0.811, P < 0.001), while the fair agreement was found for quinolone resistance and gyrA mutant genes (k = 0.260–0.271, P < 0.001). No association was detected between macrolide resistance and point mutations in the 23S rRNA gene. These findings fill knowledge gaps on AMR in Campylobacter in Thailand, emphasizing the need for targeted AMR mitigation strategies in both commercial broilers and native chickens.

RESEARCH HIGHLIGHTS

• High Campylobacter prevalence in chickens; C. jejuni more prevalent than C. coli.

• Susceptibility to macrolides but resistance to quinolones/tetracyclines in isolates.

• Homogeneous resistance patterns within farms; higher in broilers than in native birds.

• Partial association between phenotypic and genotypic resistance among isolates.

KEYWORDS:

• Antimicrobial resistance
• Campylobacter
• commercial broilers
• genotype
• native chickens
• phenotype
• Thailand

Acknowledgements

The authors would like to thank all farmers involved in the study for their willing participation in this project. Thanks to Walailak University Ph.D. Scholarships for High Potential Candidates to Enroll in Doctoral Programs (Contract No. HP009/2021) awarded to Hoang Phu Doan (Doan Hoang Phu). We thank the staff at the Center of Excellent Research for Melioidosis (CERM), Walailak University, Thailand, for their support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Thailand Science Research and Innovation Fund [grant number FRB650082/0227] and The Office of the Permanent Secretary of the Ministry of Higher Education, Science, Research and Innovation awarded to Assoc. Prof. Dr. Thotsapol Thomrongsuwannakij; and the Walailak University Graduate Studies Research Fund [grant number CGS-RF 2022/09] awarded to Hoang Phu Doan (Doan Hoang Phu).