Purpose: This study determined the prevalence of Campylobacter in raw cow milk in Flanders, both by conventional culturing and molecular techniques to include detection of nonculturable strains/species.
Methods: Two hundred raw milk tank samples were collected in Flanders. Bacteriological analysis was performed according to ISO10272-1, but with Bolton Broth and Preston Broth, in parallel. To detect nonculturable Campylobacters, DNA was extracted from the raw milk samples. Beforehand, two commercial kits (PowerFood, Mobio Laboratories and AdiaPure, Biomérieux) were evaluated to determine their detection limit for Campylobacter DNA extracted from inoculated milk. The kit that performed best was used to extract DNA from the 200 milk samples. This DNA was used for Campylobacter genus detection.
Results: By conventional culturing, a prevalence of 0.5% was noted with Bolton Broth and 1% with Preston Broth. The isolates were identified as Campylobacter jejuni. The AdiaPure kit, with a detection limit of 1,000 cfu Campylobacter/ml raw milk, performed best. But, none of the 200 samples were positive after DNA extraction and PCR; meaning that the number of Campylobacter in the milk samples was below the detection limit of the kit and PCR.
Significance: By conventional culture, a prevalence of 1% was noted, which is quite low compared to the prevalences reported in other countries. Further, this study showed that molecular methods were not able to detect Campylobacter, culturable or nonculturable, in raw milk. So, the true prevalence may be higher, although the number of Campylobacter may be low. Considering the low infection dose of Campylobacter, consuming raw milk is not recommended.