Incidence, intraspecific diversity and toxigenic profile of Bacillus cereus in the yellow-water, a fermented food flavor enhancer

Abstract

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 × 103- 4.9 × 103 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 entFM were 94%, 88%, 46% and 70%, respectively. All isolates with nheABC could produce NHE, 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.