Prevalence of Bacillus cereus and Associated Risk Factors in Chinese-Style Fried Rice Available in the City of Colombo, Sri Lanka

The present study aimed to assess the prevalence of Bacillus cereus and its associated risk factors in Chinese-style fried rice available in Colombo city. In 200 samples of fried rice the prevalence of B. cereus was 56%. The prevalence by variety of fried rice was chicken (20.0%), vegetable (18.0%), seafood (10.0%), egg (5.0%), mixed (2.0%), and beef (1.0%). Of analyzed samples, 28 (14%) had colony counts > 10(6) colony forming units per gram (cfu/g), the infectious dose for B. cereus food borne outbreaks. Occurrence of > 10(6) cfu/g of B. cereus were associated with storage of boiled rice at room temperature (p = 0.030), >4 hours of storage at room temperature (p = 0.042) and cooking frequency of more than once per dining session (p = 0.017). The type of rice and the quantity boiled per day were not independent risk factors for high B. cereus counts. Majority of B. cereus isolates (53.7%) in this study were not typable. The serotypes observed included H15 (14.3%), H19 (14.3%), and H20 (10.7%). These serotypes are known to be associated with both emetic and diarrheal syndromes. All isolates were sensitive to ciprofloxacin (100%), erythromycin (100%), gentamicin (100%), chloramphenicol (100%), and amikacin (100%) whereas 100% resistance was observed for penicillin with minimal inhibitory concentration range of 32-256 mu g/mL.