Effect of high-temperature, short-time (HTST) pasteurization on milk containing low numbers of Mycobacterium paratuberculosis |
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Authors: | Grant Ball & Rowe |
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Institution: | Department of Food Science (Food Microbiology), The Queen's University of Belfast,;Veterinary Sciences Division, Department of Agriculture for Northern Ireland, Belfast, Northern Ireland, UK |
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Abstract: | The efficacy of high-temperature, short-time (HTST) pasteurization (72 °C/15 s) when low numbers (≤ 103 cfu ml ?1 ) of Mycobacterium paratuberculosis are present in milk was investigated. Raw cows' milk spiked with Myco. paratuberculosis (103 cfu ml?1, 102 cfu ml?1, 10 cfu ml?1, and 10 cfu 50 ml?1) was subjected to HTST pasteurization using laboratory pasteurizing units. Ten bovine strains of Myco. paratuberculosis were tested in triplicate. Culture in BACTEC Middlebrook 12B radiometric medium detected acid-fast survivors in 14·8% and 10% of HTST-pasteurized milk samples at the 103 and 102 cfu ml?1 inoculum levels, respectively, whereas conventional culture on Herrold's egg yolk medium containing mycobactin J detected acid-fast survivors in only 3·7% and 6·7% of the same milk samples. IS900-based PCR confirmed that these acid-fast survivors were Myco. paratuberculosis . No viable Myco. paratuberculosis were isolated from HTST-pasteurized milk initially containing either 10 cfu ml?1 or 10 cfu 50 ml?1. |
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