Isolation and identification of Campylobacter jejuni from poultry carcasses using conventional culture methods and multiplex PCR assay

Campylobacter jejuni is a major cause of food-borne diarrhea in many countries. Poultry and poultry products are known as important sources of human campylobacteriosis. In this study, conventional culture and multiplex PCR methods were compared for the detection of C. jejuni isolated from poultry carcasses. A total of 100 samples, representing 20 broiler flocks, were collected from poultry carcasses after the evisceration stage in the processing line at a commercial broiler slaughtering facility in Mashhad, Iran. In the conventional culture method, samples were processed by enrichment followed by selective plating, and then suspected colonies were isolated on sheep blood agar and tested for morphology, motility, Gram staining, biochemical properties and hippurate hydrolysis activity. For the identification of the Campylobacter genus and its jejuni serovar by molecular methods, a multiplex PCR assay (m-PCR) with two sets of specific primers was used. In the hippurate hydrolysis test of suspected colonies, 76% of the samples were determined as positive, while in the m-PCR assay 28% of cultures harvested were identified as C. jejuni. Two percent of hippurate hydrolyze negative colonies were found positive in the m-PCR test.
It appears that the conventional method, based on the hippurate hydrolysis test for detection of C. jejuni, is a less reliable test. The use of the m-PCR method, based on amplification from conserved genes, allows reliable detection and identification of C. jejuni.