IngentaConnect Survey of Ontario Bulk Tank Raw Milk for Food-Borne Pathogens

Authors: Steele, Marina L.¹; McNab, W. Bruce¹; Poppe, Case²; Griffiths, Mansel W.³; Chen, Shu¹; Degrandis, Stephanie A.¹; Fruhner, Lynne C.¹; Larkin, Carolyn A.¹; Lynch, John A.¹; Odumeru, Joseph A.¹

Source: Journal of Food Protection®, Volume 60, Number 11, November 1997 , pp. 1341-1346(6)

Publisher: International Association for Food Protection

Abstract:

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, excluding spore-forming bacteria and possibly Mycobacterium paratuberculosis, but some people continue to drink raw milk, believing it to be safe. 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 proportion of pick-ups (loads of raw milk from a single farm bulk tank) from Ontario farm bulk tanks that contained Listeria monocytogenes, Salmonella spp., Campylobacter spp., and/or verotoxigenic Escherichia coli (VTEC). Samples from 1,720 pick-ups of raw milk were tested for the presence of these pathogens, and 47 L. monocytogenes, three Salmonella spp., eight Campylobacter spp., and 15 VTEC isolates were detected, representing 2.73, 0.17, 0.47, and 0.87% of milk samples, respectively. Estimates of the proportion of theoretical tanker truck loads of pooled raw milk contaminated with pathogens ranged from a low of 0.51% of tankers containing raw milk from 3 bulk tanks being contaminated with Salmonella spp. to a high of 34.41% of tankers containing raw milk from 10 bulk tanks being contaminated with at least one of the pathogens. Associations between the presence of pathogens and raw milk sample characteristics were investigated. The mean somatic cell count was higher among VTEC- or L. monocytogenes-positive samples, and the mean aerobic plate count was found to be higher among L. monocytogenes-positive samples. These results confirm the presence of bacterial food pathogens 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.

Keywords: RAW MILK; SALMONELLA; LISTERIA MONOCYTOGENES; CAMPYLOBACTER; VEROTOXIGENIC ESCHERICHIA COLI

Document Type: Research article

Affiliations: 1: Ontario Ministry of Agriculture, Food, and Rural Affairs, Agricultural and Food Laboratory Services Center, 95 Stone Rd. West, zone 2, Guelph, Ontario, N1H 8J7 2: Health Canada, Health of Animals Laboratory, Guelph, Ontario, Canada N1G 3W4 3: University of Guelph, Food Science Department, Guelph, Ontario, Canada N1G 2W1

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