Presence of Escherichia coliO157, Salmonellaspp., and Listeria monocytogenesin Raw Ovine Milk Destined for Cheese Production and Evaluation of the Equivalence Between the Analytical Methods Applied

AbstractItaly is one of the main producers and exporters of cheese made from unpasteurized sheep milk. Since raw milk and its derived products are known sources of human infections, cheese produced from raw sheep milk could pose a microbiological threat to public health. Hence, the objectives of the study were: to characterize the potential risk of the presence of pathogens Escherichia coliO157, Listeria monocytogenes, and Salmonellain raw ovine milk destined for cheese production obtained from all the sheep farms (n = 24) in the Marches region (Central Italy) that directly transform raw milk into cheeses and to evaluate the equivalence between the analytical methods applied. A three-step molecular method (simultaneous culture enrichment, species-specific DNA magnetic isolation, and multiplex real-time polymerase chain reaction) was used for milk (n = 143) and cheese (n = 5) analysis over a 3-year period. L. monocytogeneswas not detected on any of the farms, while E. coliO157 was found on three farms, although only using the molecular method. Four farms tested positive for Salmonellaspp., and Salmonella entericasubsp. diarizonae serovar 61:k:1,5,7 was isolated in one of those cases. This information highlights the need to develop preventative measures to guarantee a high level of consumer safety for this specific product line, and the molecular method could be a time-saving and sensitive tool to be used in routine diagnosis.