Staphylococcus aureus in raw milk and human health risk

Staphylococcus aureus is a contagious pathogen, the epidemiological pattern of which is strongly influenced by bacterial characteristics and host susceptibility. Amongst the characteristics, a very important one is represented by irregular shedding pattern that complicates the diagnosis and, very probably, plays an important role in the diffusion of strains within herds. These features could also influence the distribution of enterotoxin-producing strains. The probability of obtaining milk contaminated by Staphylococcus aureus is relatively high, but heat treatment could easily control this contamination. The risk could be different when raw milk and raw milk cheeses are considered. Indeed, Staphylococcus aureus inoculated in raw milk could multiply during manufacturing and ripening, even when the initial counts are low. It has been demonstrated that soft cheese produced with milk inoculated with SEE-producing Staphylococcus aureus could contain enterotoxin in a quantity sufficient to be harmful to humans.