Abstract:
The objectives of the present study were to examine the occurrence and persistence of Campylobacter in consecutive broiler flocks and to determine antimicrobial resistance patterns of Campylobacter isolated from conventional broilers reared consecutively. A total of 1,859 broiler and environmental samples were collected from 2 broiler farms located in the eastern part of Thailand for 3 production cycles. Campylobacter isolated strains were selected and genotyped by flaA short variable region (flaA SVR) sequencing and multilocus sequence typing (MLST). Furthermore, these Campylobacter isolates were tested for their antimicrobial resistance to 5 antimicrobial agents by the agar dilution method. The results showed that broilers in farm A and farm B were Campylobacter positive in the first (A1, 51.76%) and the second (A2, 51.05%) production cycles and in the first (B1, 25.29%) and the third (B3, 39.42%) production cycles, respectively. Although a high degree of genetic diversity was noticed in Campylobacter isolates from flock A1, only one genotype was found in flock A2. Unlike farm A, a single Campylobacter genotype, flaA SVR allele number 783 (ST-1232), was observed in farm B from both positive flocks. Moreover, the genotype that was present in environment was also detected in broilers. In the present study, the majority of Campylobacter isolates were resistant to ciprofloxacin (94.86%), followed by tetracycline (88.78%) and ampicillin (56.07%). In contrast, low rates of resistance were found for erythromycin (7.01%) and gentamicin (6.07%). The most common resistance patterns observed in this study were CIP-TET-AMP (43.92%) and CIP-TET (34.11%). Our findings suggested that certain clone of Campylobacter may survive and persist in the farm environment, then recontaminate the following flocks. In addition, the routine practice of antimicrobial usage as reported in this study may influence the occurrence of antimicrobial-resistant Campylobacter in conventional broiler production. Therefore, it is necessary to implement the control strategies, especially cleaning and disinfection measures, in order to reduce the contamination of Campylobacter between flocks. Moreover, the prudent use of antibiotics in broiler production should also be emphasized.
