Bacillus cereus and Bacillus thuringiensis spores in Korean rice: Prevalence and toxin production as affected by production area and degree of milling

Booyoung Kim, Jihyun Bang, Hoikyung Kim, Yoonsook Kim, Byeong sam Kim, Larry R. Beuchat, Jee Hoon Ryu

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

We determined the prevalence of and toxin production by Bacillus cereus and Bacillus thuringiensis in Korean rice as affected by production area and degree of milling. Rough rice was collected from 64 farms in 22 agricultural areas and polished to produce brown and white rice. In total, rice samples were broadly contaminated with B.cereus spores, with no effect of production area. The prevalence and counts of B.cereus spores declined as milling progressed. Frequencies of hemolysin BL (HBL) production by isolates were significantly (P≤0.01) reduced as milling progressed. This pattern corresponded with the presence of genes encoding the diarrheal enterotoxins. The frequency of B.cereus isolates positive for hblC, hblD, or nheB genes decreased as milling progressed. Because most B.cereus isolates from rice samples contained six enterotoxin genes, we concluded that B.cereus in rice produced in Korea is predominantly of the diarrheagenic type. The prevalence of B.thuringiensis in rice was significantly lower than that of B.cereus and not correlated with production area. All B.thuringiensis isolates were of the diarrheagenic type. This study provides information useful for predicting safety risks associated with B.cereus and B.thuringiensis in rough and processed Korean rice.

Original languageEnglish
Pages (from-to)89-94
Number of pages6
JournalFood Microbiology
Volume42
DOIs
Publication statusPublished - 2014 Sep

Keywords

  • B acillus cereus
  • B acillus thuringiensis
  • Enterotoxin
  • Milling
  • Rice

ASJC Scopus subject areas

  • Food Science
  • Microbiology

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