Molecular Detection of Milk borne Bacterial Disease
Date Issued
2012
Date
2012
Author(s)
Chiou, Hung-Shi
Abstract
Milk is a nutritious food for humans and animals because it contains several important nutrients, including proteins and vitamins, but it also serves as a good medium for the growth of many microorganisms, especially bacterial pathogens. The major food-borne pathogens in humans include Salmonella enterica subspecies enterica serovar Typhimurium, Listeria monocytogenes, Staphylococcus aureus, Campylobacter jejuni, and Escherichia coli O157:H7. Milk consumption is also considered as an important transmission pathway for various diseases to animals and humans. Non-pasteurized milk is by far the most probable vehicle for the transmission of pathogenic mycobacteria, including Mycobacterium bovis and M. avium subsp. Paratuberculosis. Potential hazard exists in the commercial milk products since bacterial endotoxin could not completely be destroyed by current pasteurization methods. In order to evaluate the potential of milk-borne bacterial diseases via raw and pasteurized milk, molecular detecting methods were developed for potential milk-borne bacterial pathogens. Polymerase chain reaction with specific primer sets was used to detect specific genes of Mycobacterium spp., M. bovis, M. paratuberculosis, S. Typhimurium, L. monocytogenes, C. jejuni, S. aureus, and E. coli O157, and in milk. There were a total of 12 and 461 raw milk samples obtained from 12 tuberculin skin test-positive dairy cows in 2 dairy farms (group I) and 461 tuberculin skin test-negative dairy cows and goats from 5 dairy farms (group II). In addition, 80 commercialized pasteurized milk products were also collected from 5 brands (group III) during the surveyed period. Mycobacterium spp. and Staphylococcus aureus were the most predominant bacteria and/or bacterial toxin detected in all sample groups. The positive rates of HSP65 were 66.8%, 14.1%, and 40.0% in group I, II, and III, respectively; with a significantly higher positive rate in ITT-positive than in ITT-negative raw milk samples and in pasteurized milk than in ITT-negative raw milk samples. The positive rates of Nuc gene were 50.0%, 16.5, and 13.8 in groups I, II, and III, respectively it was significantly higher in ITT-positive raw milk samples than in ITT-negative raw milk samples and pasteurized milk samples, but there was no difference between ITT-negative raw milk samples and pasteurized milk samples. One M. bovis-positive raw milk sample was detected in group I and one S. Typhimurium-positive raw milk sample was detected in group II. Owing to the presence of detectable HSP65 and Nuc in both raw milk samples and commercial pasteurized milk products, the risk of bacterial contamination is present; however, a definitive confirmation of the presence of live bacteria in the milk should rely on bacterial culture. Since M. bovis could be detected in the raw milk samples, the dairy workers should follow the procedure of pasteurization of the colostrum restrictively prior to feeding it to calves to eliminate the possible transmission of bacterial pathogens through milk to calves. It is speculated that there might be failure in pasteurization or negligence in the procedure; therefore, the management of enterprise, and efforts from the government and the entire productive chain are required to attain consumer’s safety.
Subjects
cow raw milk
pasteurized milk
milk borne bacteria
nuclear acid detection
PCR
SDGs
Type
thesis
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