Foodborne Pathogens in In-Line Milk Filters and Associated On-Farm Risk Factors in Dairy Farms Authorized To Produce and Sell Raw Milk in Northern Italy

All dairy farms authorized to produce and sell raw milk in a province of Northern Italy were investigated to determine the presence of Campylobacterspp., verocytotoxin-producing Escherichia coli(VTEC), Listeria monocytogenes, and Salmonellaspp. in in-line milk filters and to assess their association with suspected risk factors on farms. A logistic regression model was used to analyze data collected describing the characteristics and management practices of 27 farms and the microbiological status of 378 in-line milk filters by both culture-based and molecular methods. Thermotolerant Campylobacter, VTEC, and L. monocytogeneswere detected in 24 (6.45%), 32 (8.4%), and 2 (0.5%) samples, respectively. No Salmonellaspp. were detected. For risk analysis, data of L. monocytogenesand Salmonellaspp. were not included in the model because of the low prevalence or absence of these organisms. The univariate analysis disclosed that the presence of VTEC and/or Campylobacterspp. in milk filters was associated with lack of cleanliness of bedding, water trough, and feed trough; nonevaluation of water hardness; lack of cleanliness of milk tank; and nonapplication of forestripping. After multivariate analysis, an association was observed with inadequate cleanliness of bedding and milk tank and the nonapplication of forestripping. PCR analysis of milk filters was a rapid and sensitive method for the microbiological evaluation of herd contamination status and should be included among the registration requirements for the authorization to produce and sell raw milk. Specific control actions must be incorporated into the farmer's daily practices to ensure the low-risk production of raw milk.