Potentially pathogenic Staphylococcus aureus and Listeria spp. in Brazilian unpasteurized cheese production

This study aimed to identify potentially pathogenic microorganisms (Listeria innocua, L. seeligeri, L. ivanovii, L. monocytogenes, Staphylococcus aureus, and several virulence genes) in unpasteurized cheese production in the northeastern region of the state of So Paulo, Brazil. Listeria species were detected in 68 (64.14%) out of 106 samples of bovine feces, swabs from milkers' and cheese handlers' hands, milking buckets, raw milk, whey, water, cheese processing surface,s and utensils. All the samples collected at one farm were contaminated with Listeria spp. L. innocua, L. seeligeri, L. ivanovii, or L. monocytogenes were not detected in the samples collected in this study. A set of 391 Staphylococcus spp. isolates were obtained in these samples, from which 60 (15.31%) were identified as S. aureus using PCR (Polymerase Chain Reaction). S. aureus carrying virulence genes (eta, hlg, seg, seh, sei) were detected in milk, in swabs from cheese handler's hands, whey, milk, sieves, buckets, and cheese. The hlg gene (encodes gamma hemolysin) was detected in all the S. aureus isolates. These findings show that poor hygienic practice is associated with a higher risk of pathogenic bacteria in milk or cheese, providing useful information for public health authorities to increase food safety surveillance and prevent the dissemination of pathogens.