OCCURRENCE AND TOXIN GENE PROFILE OF BACILLUS CEREUS IN DAIRY PRODUCTS

Abstract

Bacillus cereus, a bacteria frequently associated with food spoilage, is responsible for 2 different foodborne illness in humans: a diarrheal disease, associated with cytotoxin K, hemolysin BL and a non-hemolytic enterotoxin, and an emetic syndrome, associated with the cereulide toxin. The aim of this study is to investigate the occurrence of B. cereus in 515 hard and soft cheeses collected in southern Italy. The strains were molecularly characterized for the presence of hblA, hblC, hblD, nheA, nheB, nheC, cytK, and entFM genes, related to the production of enterotoxins (trimeric hemolysin BL, trimeric non-hemolytic enterotoxin, cytotoxin K and enterotoxin FM). One hundred thirty eight samples (26.8%) were found contaminated by B. cereus. One hundred of the contaminated samples (72.5%) showed a level of B. cereus contamination <103 CFU/g, whereas 9 (6.5%) samples showed a contamination >105 CFU/g. Seven different molecular profiles were found among the 138 strains of B. cereus isolated. The most common profile was nheABC-entFM, found in 42 strains, followed by the hblACD-nheABC-cytK-entFM, found in 33 strains, the nheABC-cytK-entFM, found in 24 strains, the hblACD-nheABC-entFM, found in 11 strains, the hblACD-nheAC-entFM, found in 15 strains, and the nheC-entFM, found in 12 strains. Eleven strains did not harbored any of these genes. In 7.2% (37/515) of samples, characterized by a bacterial contamination >103 CFU/g, we found B. cereus strains harboring genes encoding for at least one complete enterotoxin.