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A case of sporadic ovine mastitis caused by Listeria monocytogenes and its effect on contamination of raw milk and raw-milk cheeses produced in the on-farm dairy

  • Dagmar Schoder (a1), Petra Winter (a2), Abdoulla Kareem (a1), Walter Baumgartner (a2) and Martin Wagner (a1)...

Abstract

We describe a case of listerial mastitis in a flock of 130 sheep. The animals were housed at a farm where the bulk raw ewe milk was processed to produce raw milk soft cheese. List. monocytogenes was shed from the right mammary complex. Shedding was observed over a period of 99 d. A mean level of 4·56×104 cfu (colony forming units) Listeria monocytogenes/ml was recovered from the raw milk originating from the infected udder. The numbers ranged from 9×101 to 2·95×105. The bulk milk was contaminated by approx. 5·7×103 cfu/ml. In the cheese product, 2·0×102 cfu List. monocytogenes/g were constantly detectable for a period of 7 d post manufacture. The starter culture used for coagulation had a pivotal influence on the behaviour of List. monocytogenes during cheesemaking. Using the same mesophilic buttermilk culture as used by the farmer allowed numbers of Listeria to increase 60-fold within 12 h owing to a delayed acidification of the bulk milk. Addition of a thermophilic yogurt culture reduced the numbers of Listeria within 8 h of incubation.

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A case of sporadic ovine mastitis caused by Listeria monocytogenes and its effect on contamination of raw milk and raw-milk cheeses produced in the on-farm dairy

  • Dagmar Schoder (a1), Petra Winter (a2), Abdoulla Kareem (a1), Walter Baumgartner (a2) and Martin Wagner (a1)...

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