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.
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 x 10(4) cfu (colony forming units) Listeria monocytogenes/ml was recovered from the raw milk originating from the infected udder. The numbers ranged from 9 x10(1) to 2.95 x 10(5). The bulk milk was contaminated by approx. 5.7 x 10(3) cfu/ml. In the cheese product, 2.0 x 10(2) 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.
Schoder
Dagmar
D
Institute for Milk Hygiene, Milk Technology and Food Science, University for Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria.
Winter
Petra
P
Kareem
Abdoulla
A
Baumgartner
Walter
W
Wagner
Martin
M
D000818:Animals; D002611:Cheese / Q000382:microbiology*; D015169:Colony Count, Microbial / Q000662:veterinary; D003257:Consumer Product Safety; D003612:Dairying / Q000379:methods / Q000592:standards; D005260:Female; D005506:Food Contamination; D005516:Food Microbiology; D006920:Hygiene; D008089:Listeria monocytogenes / Q000302:isolation & purification; D008088:Listeriosis / Q000382:microbiology / Q000635:transmission / Q000662:veterinary*; D008413:Mastitis / Q000382:microbiology / Q000662:veterinary*; D008892:Milk / Q000382:microbiology*; D012756:Sheep; D012757:Sheep Diseases / Q000382:microbiology* / Q000635:transmission; D013997:Time Factors