Analysis of enterotoxin production by Staphylococcus aureus in Minas Frescal Cheese under different intrinsic and extrinsic factors

Abstract

Staphylococcus aureus is a foodborne associated pathogen, mainly in dairy products due to the enterotoxin production. This study analyzed the production of classical toxins in cheese by S. aureus, in different temperatures, atmospheres, and levels of contamination. Minas Frescal Cheese were classified according to their microbiota. The cheese samples were classified as low or high level of contamination according to the concentration of that bacteria. An aliquot of 10 5 CFU of each strain (producing enterotoxin A, B, C, or D) in BHI was inoculated into two types of commercial cheeses presenting low and high contamination. Therefore, the samples were incubated at 8 °C, 15 °C, and 35 °C for 24, 48 and 72 hours in aerobic and anaerobic condition. The detection and quantification of enterotoxins were tested against toxin A, B, C and D using reverse passive latex agglutination. There was no enterotoxin production at 8 °C in all treatment, consequently, no statistically significant difference was observed. At 15 °C, the SEA production was significantly higher (p<0.05) in BHI broth than in cheese with low contamination in all three times evaluated. Regarding SEB, in aerobic condition at 15 °C after 72 hours, the BHI broth showed significantly higher production than the low contaminated cheese. S. aureus produced a different range of enterotoxin according to the substrate. In BHI, the production was higher than in cheese, suggesting that food substrates more appropriate to analyze the real enterotoxin production. Besides, the microbiota presents can interfere in its production.