GENETIC DIVERSITY AND PREVENTION OF CAMPYLOBACTER SPP. IN BROILER BREEDERS AND BROILERS

Abstract

Contaminated poultry meat is regarded as the main source of human campylobacteriosis. In Thailand, there is only a few publications studied in poultry farms, so the aims of this study were 1) to identify the relationship of Campylobacter isolates among broiler breeders, broilers and their environments, 2) to examine antimicrobial resistance profiles of Campylobacter spp., and 3) to examine the protection of competitive exclusion after challenging Campylobacter jejuni in broilers. To complete the objectives, there were 2 parts in this study. First, five commercial breeder flocks, 2 hatcheries, and 5 broiler flocks were sampled. Thirty-six C. jejuni and 94 C. coli isolates collected through two broiler production chains were tested by two-fold agar dilution for their susceptibility to antimicrobial agents. Most Campylobacter isolates were multidrug resistance (MDR) (C. jejuni: 100%; C. coli: 98.9%), and exhibited high resistance to enrofloxacin (C. jejuni: 100%; C. coli: 98.9%). A selected subset of 24 C. jejuni and 24 C. coli were characterized for their mutations in the quinolone resistance determining region (QRDR) of the gyrA gene by nucleotide sequence analysis. The Thr-86-Ile substitution (ACA-ATA in C. jejuni or ACT-ATT in C. coli) was found in all isolates. Horizontal transmission was the major route of Campylobacter transmission in this study, as all Campylobacter isolates were typed and ten distinct clusters were recognized by flaA-RFLP typing. Second, competitive exclusion (CE) were identified from 60 adult chicken feces of native chickens and organic layers raised under non-antimicrobial usage farms. Lactobacillus spp., Bacillus spp. and Enterococcus faecium were identified and tested their antimicrobial susceptibilities for preventing transmissible antimicrobial resistance, as recommended by EFSA. Furthermore, those isolates were in vitro tested for acid and bile tolerances. Lactobacillus acidophilus 1/4, Bacillus subtilis 206/1 and Enterococcus faecium 122 demonstrated their powerful in vitro activities and were, therefore, used as CE during oral gavage of 1-day-old broilers for 3 days consecutively. After C. jejuni challenges at 14 days in broilers, the treatment groups had no significant differences in C. jejuni re-isolations or feed conversion ratio at 41 days. In conclusions, the emergence of MDR and high resistance rates to several antimicrobials are major concerns identified in this study. The prudent use of these agents and active surveillance of resistance at the farm level are essential steps to reduce the public health risks identified in this work.