Incidence, Intraspecific Diversity and Toxigenic Profile of Bacillus cereus in the Yellow-Water, a Fermented Food Flavor Enhancer

摘要

The incidence, intraspecific diversity and toxigenic profile of Bacillus cereus in the Yellow-Water were investigated. Of 50 samples tested, 17 (34%) were contaminated by B. cereus with 3.7 x 10(3) - 4.9 x 10(3) CFU/mL. The intraspecific diversity of B. cereus was observed by repetitive (GTG)(5) sequence polymorphism-PCR, with six subtypes, and were further discriminated into seven subtypes by 16S-23S rRNA intergenic transcribed spacer. 94% of isolates contained at least 2 toxin genes of nheABC, hblCDA, cytK, entFM and EM1, but 6.0% carried none of them. The detection rates of nheABC, hblCDA, cytK and etztFM were 94%, 88%, 46% and 70%, respectively. All isolates with nheABC could produce NEE, but of the isolates harbored hblCDA, 52% was positive for HBL. Only 6.0% isolates possessed EM1 and they were positive for emetic toxin assay. The results suggested that Yellow-Water needs stricter microbial standard as a fermented food flavor enhancer.