Appropriate Campylobacter detection method and genetic variation of Campylobacter jejuni in broilers

Abstract

Campylobacter has been known as an important cause of gastroenteritis in humans. The primary source is raw or undercooked poultry meat. Previous study showed that Campylobacter isolated from slaughterhouses were associated with Campylobacter isolated from broiler farms. Thus, detection of Campylobacter flock status and sorting flocks prior to slaughtering processes may help prevent Campylobacter contamination between Campylobacter-positive and negative flocks during slaughtering processes. Unfortunately, appropriate sample type and isolation method have not been clearly specified for Campylobacter detection at the farm level. Because Campylobacter are fastidious bacteria, improper detection method can attribute to false negative results. Therefore, the objectives of this study were 1) to identify appropriate sample type and isolation method for Campylobacter detection in broilers and 2) to determine genetic relatedness of C. jejuni from different broiler houses in the same farm. This study consists of 2 experiments. In the first experiment, three types of sample were obtained from 60 broiler houses including 60 boot swabs, 60 cloacal swabs and 60 fresh fecal samples. Campylobacter were isolated from cloacal swab and fresh fecal samples by direct plating method using modified Charcoal-Cefoperazone-Deoxycholate Agar (mCCDA), modified Karmali (mKarmali), Preston agar and Campy-cefex agar. Isolation of Campylobacter from boot swabs was conducted by both direct plating method and selective enrichment method using Bolton broth, Preston broth, Exeter broth and blood-free Bolton broth as selective enrichment. To determine the most suitable sample type, only Campylobacter isolation rates from direct plating method were compared. The difference in Campylobacter isolation rate was analyzed by McNemar test (p<0.05). The results showed that boot swabs provided the highest Campylobacter isolation rate at 26.7%, followed by cloacal swabs (20%) and fresh feces (15%). Among the media used, mCCDA is better than the other media tested for Campylobacter isolation from farm samples. In addition, our results revealed that using Preston agar as the second media along with mCCDA could significantly increase Campylobacter isolation rate. For the second experiment, boot swabs were obtained from 60 houses of 12 broiler farms (5 houses/farm). Genetic relatedness of C. jejuni isolated from each broiler house within each broiler farm was examined by Comparative Genomic Fingerprint 40 (CGF40). The results showed that Campylobacter-positive and Campylobacter-negative houses were observed in each broiler farm. Although specific CGF40 patterns were noticed among C. jejuni isolated from each broiler farm, C. jejuni from broiler houses in the same farm had quite similar CGF40 patterns. According to our findings, we suggest that boot swabs should be collected from a few or more houses in the same farm and Campylobacter detection should be conducted by direct plating of boot swab samples onto both mCCDA and Preston agar. Campylobacter detection at the farm level by using appropriate sample type and isolation method is important to correctly obtain Campylobacter flock status and sort flocks prior to slaughtering, which can significantly help decrease Campylobacter cross-contamination during slaughtering processes.