SURVEY OF ONTARIO BULK TANK RAW-MILK FOR FOOD-BORNE PATHOGENS

Raw (unpasteurized) milk can be a source of food-borne pathogens. Raw milk consumption results in sporadic disease outbreaks. Pasteurization is designed to destroy all bacterial pathogens common to raw milk, ex cluding spore-forming bacteria and possibly Mycobacterium paratubercul osis, but some people continue to drink raw milk, believing it to be s afe. Current methods for assessing the bacteriological quality of raw milk, such as aerobic plate counts, are not usually designed to detect specific pathogens. The objective of this study was to estimate the p roportion of pick-ups (loads of raw milk from a single farm bulk tank) from Ontario farm bulk tanks that contained Listeria monocytogenes, S almonella spp., Campylobacter spp., and/or verotoxigenic Escherichia c oli (VTEC). Samples from 1,720 pick-ups of raw milk were tested for th e presence of these pathogens, and 47 L. monocytogenes, three Salmonel la spp., eight Campylobacter spp., and 15 VTEC isolates were detected, representing 2.73, 0.17, 0.47, and 0.87% of milk samples, respectivel y. Estimates of the proportion of theoretical tanker truck loads of po oled raw milk contaminated with pathogens ranged from a low of 0.51% o f tankers containing raw milk from 3 bulk tanks being contaminated wit h Salmonella spp. to a high of 34.41% of tankers containing raw milk f rom 10 bulk tanks being contaminated with at least one of the pathogen s. Associations between the presence of pathogens and raw milk sample characteristics were investigated. The mean somatic cell count was hig her among VTEC- or L. monocytogenes-positive samples, and the mean aer obic plate count was found re be higher among L. monocytogenes-positiv e samples. These results confirm the presence of bacterial food pathog ens in raw milk and emphasize the importance of continued diligence in the application of hygiene programs within dairies and the separation of raw milk from pasteurized milk and milk products.