Sale of Raw Milk in Northern Italy: Food Safety Implications and Comparison of Different Analytical Methodologies for Detection of Foodborne Pathogens

摘要

The safety of raw milk sold in Northern Italy was investigated in relation to hygiene quality parameters andudpresence of Salmonella spp., Listeria monocytogenes, thermotolerant Campylobacter, and Verocytotoxin producingudEscherichia coli O157:H7. The performance of different analytical methods used—official culture method (ISO),udmodified Bacteriological Analytical Manual cultural method (mBAM), and polymerase chain reaction (PCR)—udwas evaluated. The presence of Mycobacterium avium subsp. paratuberculosis (Map) was investigated only byudPCR. All samples met regulations for alkaline phosphatase and inhibitory substance, while 18% and 44.8% ofudsamples collected from vending machines had, respectively, somatic cell count (SCC) > 300,000/mL and totaludbacterial count (TBC) > 50,000CFU/mL. The correlation between hygienic quality parameters in samples collectedudfrom bulk tank and vending machines showed a significant increase of TBC in vending machines meaningudthat raw milk was mishandled during distribution and sale. All pathogens investigated were detected in rawudmilk sold at vending machines; a total of five samples (5%) had at least one pathogen, of which two wereuddetected by PCR and three by mBAM. None of the samples was positive by cultural ISO methods. Even if theudcomparison of analytical methods showed that none performs significantly better than the others, testing audhigher volume of milk (25 versus 210 mL) affects significantly the detection rate of pathogens. Three samplesud(3%) were positive for Map, suggesting that raw milk is a significant source of Map exposure for consumers. Theudobserved TBC increase and the detection of several pathogenic bacteria pose questions on the safety of raw milk;udthe use of ISO seems inefficient in detecting a low contamination level of pathogens in milk and consequently notudappropriate as official method for testing. In order to ensure consumer’s safety, a new approach for the raw milkudchain is required.