A Multicenter Proposal for a Fast Tool To Screen Biosecure Chicken Flocks for the Foodborne Pathogen Campylobacter

The present multi-centre study aimed at assessing the performance of air sampling as a novel method for monitoring Campylobacter in biosecured poultry farms. We compared, using a harmonized procedure, the bacteriological isolation protocol (ISO 10272-1:2017), and a real-time PCR method on air filter samples. Air samples and boot swabs were collected from 62 biosecured flocks from five European countries during the summer of 2019. For air filters, the frequency of PCR-positive findings was significantly higher (n=36; 58%) compared to the cultivation methods (P<0.01; Standardized Residuals). The cultivation protocols (one with Bolton enrichment and one with Preston enrichment) were comparable to each other, but returned fewer positive samples (0-8%). The association between type of sample and frequency of PCR-positive findings was statistically confirmed (P<0.01; Fisher's exact test), although no culture-positive air filters were detected using direct plating. For the boot swabs, the highest number of positive samples were detected after enrichment in Preston broth (n=23; 37%), followed by direct plating after homogenization in Preston (n=21; 34%) or Bolton (n=20; 32%). It is noteworthy that the Norwegian flocks, a country known to have low Campylobacter prevalence in biosecured chicken flocks, tested negative for Campylobacter using the new sensitive approach. In conclusion, air sampling combined with real-time PCR is proposed as a multi-purpose, low-cost and convenient screening method that can be up to four times faster and four times more sensitive than the current boot-swab testing scheme used for screening biosecured chicken production.

Importance: Campylobacter bacteria are the cause of the vast majority of registered cases of foodborne illness in the industrialized world. In fact, the bacteria caused 246,571 registered cases of foodborne illness in 2018, which equates to 70% of all registered cases in Europe that year. An important tool to prevent campylobacter from making people sick is good data on where in the food chain the bacterium is present. The present study reports a new test method that quadruples the likelihood of identifying campylobacter-positive chicken flocks. It is important to identify campylobacter-positive flocks before they arrive at the slaughterhouse. This is because negative flocks may be slaughtered first in the morning in order to avoid cross-contamination along the production line.