Isolation and identification of Brucella spp., Listeria monocytogenes, Salmonella spp., and Staphylococcus aureus in unpasteurized fresh cheeses from a tropical region of the Gulf of Mexico

Brucella spp., Listeria monocytogenes, Salmonella spp., and Staphylococcus aureus are four of the most important pathogens associated with cheeseborne outbreaks. The aim of this study was to isolate and identify Brucella spp., L. monocytogenes, Salmonella spp., and S. aureus from fresh unpasteurized cheeses from a tropical region of the Gulf of Mexico. A total of 52 fresh unpasteurized cheeses from Tabasco, Mexico were analyzed for the presence of these microorganisms using conventional microbiological tests. Moreover, Brucella spp. was identified by the amplification of bcsp31 gene by polymerase chain reaction (PCR). For the identification of L. monocytogenes, the virulence factors; prfA and hlyA genes were amplified by PCR. Staphylococcal enterotoxins were determined in S. aureus strains. B. abortus was identified in 11% of the samples, L. monocytogenes in 2%, and Salmonella serogroup E in 4%. S. aureus was isolated from 36% of the cheese samples, whereas only, 17% of the samples contained S. aureus enterotoxigenic strains. This work further demonstrated that fresh cheeses might act as an important vehicle of transmission of Brucella and other pathogens. The presence of these pathogens is a potential public health risk. The use of pasteurized milk and proper hygienic practices in the processing of milk and dairy products are tools to improve the microbiological quality of these products.