Pre-PCR Enrichment and Screening of Campylobacter in Food Samples By Redox Potential Measurement

Introduction: The major sources of human Campylobacter infection are poultry meat and raw milk; therefore, efficient and rapid monitoring of Campylobacter in the milk and meat processing and retail industry is necessary. The ISO 10272-1:2006 standard method requires at least 136 h for confirmation.

Purpose:   The aim of the work was to develop a rapid method of screening the Campylobacter negative samples by redox potential monitoring during the enrichment phase, before the real-time PCR examination. The practical applicability of this rapid method was demonstrated by the examination of raw milk and broiler meat samples.

Methods: A total of 190 raw milk and 375 broiler meat samples obtained from the local market were examined by redox potential measurement. Samples of 25 ml or g were homogenized in 225 ml Bolton Broth with Bolton Selective Supplement, for selective enrichment at 41.5°C. Samples showing the characteristic redox potential change during monitoring were presumed to be Campylobacter-positive samples. Real-time PCR was used for species identification of Campylobacter positive samples. The results were compared to those achieved by the ISO standard method.

Results:  The limit of detection of Campylobacter was 1 cfu/sample. In the case of negative samples, the results were be achieved in 38 h by redox potential monitoring. At 5 x 10² cfu/g, which is the infective dose of Campylobacter, only 12.5 h was needed. There have been neither false positive nor false negative test results.

Significance: Use of redox potential monitoring as an enrichment method significantly decreases the time, cost, and labour requirement of detecting Campylobacter spp. in food. This method is fully compatible with the ISO standard, providing results more rapidly and cost-effectively.