The Thai Journal of Veterinary Medicine


This study aimed to identify competitive exclusion (CE) isolated from native chickens and organic layers raised under non-antimicrobial usage farms. The protection of CE was tested against Campylobacter jejuni challenges in broilers. Lactobacillus spp., Bacillus spp. and Enterococcus faecium were identified from 50 adult chicken feces of those farms. According to antimicrobial-resistance concerns of European Food Safety Authority (EFSA), the use of CE that is susceptible to antimicrobials is preferred. The numbers of Lactobacillus spp., Bacillus spp. and Enterococcus faecium equal to 195, 93 and 58 strains, respectively, were tested for their minimum inhibitory concentrations (MICs) of 10 antimicrobials. As a result, only 51 isolates passed these criteria and were further in vitro tested for acid and bile tolerances. Lactobacillus acidophilus 1/4, Bacillus subtilis 206/1 and Enterococcus faecium 122 demonstrated their powerful activities and were, therefore, used as CE during oral gavage of 1-day-old broilers for 3 days consecutively. Then, at 14 days old the broilers were challenged with a Thai field strain, CU11 of C. jejuni. As a result, the treatment groups had no significant differences in C. jejuni re-isolations or feed conversion ratio at 41 days. However, body weight of the broilers in group 8, which were orally gavaged with a commercial CE, was significantly higher than that in groups 1 and 2, which were orally gavaged with L. Acidophilus 1/4 and B. subtilis 206/1, respectively, and group 10, which was the negative control. The results showed that these CE were not able to compete against C. jejuni challenges in the broilers, which might be the result of the pathogenesis of C. jejuni, primarily colonizing the mucosal layer and not invading the intestinal cells of chickens.

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