The subproject addressed intervention studies to reduce
MRSAshort forMethicillin-resistant Staphylococcus aureus on dairy farms and tenacity studies on
MRSAshort forMethicillin-resistant Staphylococcus aureus in raw milk and during the production of raw milk soft cheese. Intramammary pirlimycin treatment of
MRSAshort forMethicillin-resistant Staphylococcus aureus infected udder quarters can significantly increase the cure rate of affected udder quarters over the dry period, provided there are no pirlimycin-resistant
MRSAshort forMethicillin-resistant Staphylococcus aureus strains in the dairy herd. However, elimination of
MRSAshort forMethicillin-resistant Staphylococcus aureus from the mammary gland does not result in elimination of
MRSAshort forMethicillin-resistant Staphylococcus aureus from other body sites, thus, spread in the herd is only reduced but not eliminated. Studies on heat inactivation of
MRSAshort forMethicillin-resistant Staphylococcus aureus in raw milk and colostrum showed that treatment at 60
°Cshort fordegrees Celsius resulted in a strong reduction of
MRSAshort forMethicillin-resistant Staphylococcus aureus levels. However, depending on the initial
MRSAshort forMethicillin-resistant Staphylococcus aureus level, heat treatment did not result in complete elimination of
MRSAshort forMethicillin-resistant Staphylococcus aureus. Heat-treated raw milk should be fed quickly to prevent re-growth of
MRSAshort forMethicillin-resistant Staphylococcus aureus in the milk. Tenacity studies of
MRSAshort forMethicillin-resistant Staphylococcus aureus in raw milk at different pH values and temperatures showed that growth depends on the pH of the raw milk, the incubation temperature, and the particular strain. Low pH values and temperatures slowed the rate of
MRSAshort forMethicillin-resistant Staphylococcus aureus multiplication in raw milk, with a pH value of 4.5 completely inhibiting
MRSAshort forMethicillin-resistant Staphylococcus aureus growth. In co-cultivation experiments with four selectedr cultures, rapid acidification of raw milk and concomitant inhibition of
MRSAshort forMethicillin-resistant Staphylococcus aureus growth was observed only with the addition of
Lactococcus lactis. Studies on soft cheese production from raw milk inoculated with
MRSAshort forMethicillin-resistant Staphylococcus aureus showed that there was a strong proliferation of
MRSAshort forMethicillin-resistant Staphylococcus aureus in the cheese at the beginning of the cheese production process, with the highest
MRSAshort forMethicillin-resistant Staphylococcus aureus bacterial count at the end of cheese ripening. This observation is also relevant with regard to toxin-producing
S.
aureus, as the cell count is crucial for toxin production.