Growth and enterotoxin production by sporeforming bacterial pathogens from spices

Spices often act as important vectors for various micro-organisms, specially sporeformers implicating possible health problems for consumers. Bacillus cereus enterotoxin (BCET) and Clostridium perfringens enterotoxin (PET) were estimated using the latex agglutination method. Seventy-four percent of the tested 23 strains of B. cereus were able to produce 8 to >256 ng BCET ml−1 brain heart infusion broth supplemented with glucose. Of the selected 16 strains of Cl. perfringens, 19% produced 2–32 ng PET ml−1 modified Duncan Strong medium. Some market spices, like cumin powder contained a high BCET titre (64 ng g−1). After intentional inoculation of black pepper powder with a toxigenic strain (120-B1) of B. cereus and 14 d-storage at room temperature, there was no significant (P<0.05) change in the cell count and BCET production. To assess safety of spicy foods, aloo dam (a potato-based food) and goat meat gravy were taken as subjects for the respective growths of B. cereus and Cl. perfringens. Freshly prepared aloo dam did not contain B. cereus, however immediate to seasoning with small cardamom the count of B. cereus cells was 533 g−1 and the BCET content was 8 ng g−1. After keeping the food at 30 °C for 21 h, the cell count increased to 106 g−1 and the BCET content increased to 128 ng g−1. A similar situation happened when aloo dam was intentionally inoculated with B. cereus 120-B1. A toxigenic strain of Cl. perfringens multiplied rapidly in the gravy; after 19 h at 37 °C the cell count increased from 103 to 107 g−1, however the PET content (2 ng g−1) remained unchanged. After boiling the 19 h-long incubated gravy for 15 min in a water bath, the cell count fell to 103 g−1 and the PET content went below the limit of detection. The results confirmed that these foods are capable of supporting outgrowth of bacterial pathogens introduced in contaminated spices and the production of enterotoxins.