Prevalence of Tetracycline-Resistant Campylobacter in Organic Broilers During a Production Cycle

Abstract

<p>Tetracycline (tet) resistance in <em>Campylobacter</em> isolated from organically raised broilers was investigated in this study. Two hundred forty-five samples from an organic broiler farm were collected weekly from the first week to the end of the production cycle, and they were cultured for thermophilic <em>Campylobacter</em>. Tetracycline resistance of these <em>Campylobacter</em> isolates was identified by the agar dilution method, whereas DNA fingerprinting profiles of tet-susceptible and tet-resistant strains were determined by pulsed-field gel electrophoresis (PFGE). None of the <em>Campylobacter</em> isolates from the third and the fourth week of the production period were resistant to tetracycline, whereas 66.7% of the isolates from the fifth week were resistant to this antibiotic. Although the prevalence of tetracycline resistance reached 100.0% during the sixth and seventh week, less than 34.0% of the isolates from the 10th week were resistant to this antimicrobial agent. In addition, only 13.8% of <em>Campylobacter</em> isolates from the intestinal tracts of these organically raised broilers were resistant to tetracycline. The presence of the <em>tet</em>(O) gene was detected in 98.9% of tet-resistant <em>Campylobacter</em> isolates, and tet-susceptible and tet-resistant <em>Campylobacter</em> strains showed distinct PFGE genotypes. The results suggest that the <em>Campylobacter</em> strains isolated from the early stage of the production were susceptible to tetracycline, but they were subsequently displaced by tet-resistant <em>Campylobacter</em>.</p>