The fate of potentially pathogenic bacteria in Swiss hard and semihard cheeses made from raw milk.

This study examined the ability of potentially pathogenic bacteria to grow and to survive during the manufacture and ripening of Swiss hard and semihard cheese varieties made from raw milk. The results show that hard cheeses are hygienically safe; 1 wk after fabrication, the inoculated pathogens (Aeromonas hydrophila. Campylobacter jejuni, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella spp., Staphylococcus aureus, and Yersinia enterocolitica) could no longer be detected. At the age of commercial ripeness, the semihard cheeses were free from the inoculated pathogens and their toxic metabolites, except for L. monocytogenes, which survived the manufacturing and ripening process.