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Applied and Environmental Microbiology, May 2002, p. 2428-2435, Vol. 68, No. 5
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.5.2428-2435.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Incidence of Mycobacterium paratuberculosis in Bulk Raw and Commercially Pasteurized Cows' Milk from Approved Dairy Processing Establishments in the United Kingdom

Irene R. Grant,1* Hywel J. Ball,2 and Michael T. Rowe1,3

Department of Food Science (Food Microbiology), Queen's University of Belfast,1 Food Science Division,3 Veterinary Sciences Division, Department of Agriculture and Rural Development for Northern Ireland, Belfast, Northern Ireland, United Kingdom2

Received 12 November 2001/ Accepted 14 February 2002

Over a 17-month period (March 1999 to July 2000), a total of 814 cows' milk samples, 244 bulk raw and 567 commercially pasteurized (228 whole, 179 semiskim, and 160 skim), from 241 approved dairy processing establishments throughout the United Kingdom were tested for the presence of Mycobacterium paratuberculosis by immunomagnetic PCR (to detect all cells living and dead) and culture (to detect viable cells). Overall, M. paratuberculosis DNA was detected by immunomagnetic PCR in 19 (7.8%; 95% confidence interval, 4.3 to 10.8%) and 67 (11.8%; 95% confidence interval, 9.0 to 14.2%) of the raw and pasteurized milk samples, respectively. Confirmed M. paratuberculosis isolates were cultured from 4 (1.6%; 95% confidence interval, 0.04 to 3.1%) and 10 (1.8%; 95% confidence interval, 0.7 to 2.8%) of the raw and pasteurized milk samples, respectively, following chemical decontamination with 0.75% (wt/vol) cetylpyridinium chloride for 5 h. The 10 culture-positive pasteurized milk samples were from just 8 (3.3%) of the 241 dairy processing establishments that participated in the survey. Seven of the culture-positive pasteurized milk samples had been heat treated at 72 to 74°C for 15 s; the remainder had been treated at 72 to 75°C for the extended holding time of 25 s. When typed by restriction fragment length polymorphism and pulsed-field gel electrophoresis methods, some of the milk isolates were shown to be types distinct from those of laboratory strains in regular use within the testing laboratory. From information gathered at the time of milk sample collection, all indications were that pasteurization had been carried out effectively at all of the culture-positive dairies. That is, pasteurization time and temperature conditions complied with the legal minimum high-temperature, short-time process; all pasteurized milk samples tested phosphatase negative; and postprocess contamination was considered unlikely to have occurred. It was concluded that viable M. paratuberculosis is occasionally present at low levels in commercially pasteurized cows' milk in the United Kingdom.

* Corresponding author. Mailing address: Department of Food Science (Food Microbiology), Queen's University of Belfast, Newforge La., Belfast BT9 5PX, Northern Ireland, United Kingdom. Phone: 00 44 28 9025 5299. Fax: 00 44 28 9025 5009. E-mail: ireneRgrant{at}hotmail.com.

Applied and Environmental Microbiology, May 2002, p. 2428-2435, Vol. 68, No. 5
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.5.2428-2435.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



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Copyright © 2002 by the American Society for Microbiology. All rights reserved.