P1-136 Isolation and Characterization of Emetic Toxin Producer Bacillus cereus from Milk Tea

Monday, July 23, 2012
Exhibit Hall (Rhode Island Convention Center)
Lee-Yan Sheen, National Taiwan University, Taipei, Taiwan
Introduction: In Taiwan, Bacillus cereus is one of the major foodborne agents of food poisoning outbreaks (125 outbreaks, during 2000-2010), and can cause diarrhea and emetic type of foodborne illness. Soft drinks made by convenient stores are popular, but they cause outbreaks with high dose and low dose of detected Bacillus cereus from time to time. Bacillus cereus positive samples can be determined their diarrhea toxins by commercial reverse passive latex agglutination (RPLA) test kit. However, none of these involved samples and strains have been determined their emetic toxin expression (cereulide) in Taiwan.

Purpose: The object of this study is to investigate the emetic toxin producing strains in soft drinks, and evaluate the toxin expression ability of these strains in culture media and food sample.

Methods: By using LC-MS method to detect emetic toxin, BCRC 17039 (ATCC 14579, cereulide producing strain), BFDA 3511, BFDA 5113, and BFDA 5511 strain can produce cereulide 347, 164, 176 and 217 ppm (TSA, 25¢J, 10 days), respectively. 

Results: Results showed the detected rate of Bacillus cereus in soft drink is 19% (29/150), and microorganisms range between 3~460 MPN/g. Among the selected Bacillus cereus (N=51), there are 3 strains (BFDA 3511, BFDA 5113, BFDA 5511) which isolated from 3 Bacillus cereus positive samples (milk-tea with herb jelly, pearl jelly and coconut jelly, separately) containing with emetic toxin producing gene. The data also revealed all 3 milk-tea isolates produced more cereulide than BCRC 17039 and BCRC 10603 (ATCC 14579, type strain) in the cooked rice after 24 hrs incubation. Furthermore, all emetic producing strains in this study, the high dose inoculation (106 CFU/g, 24 hrs) in cooked rice incubate in 25¢J produced more cereulide than in 35¢J.

Significance: According to the survey, the detected microorganisms in positive samples are in low levels yet, there is emetic toxin producer Bacillus cereus. Moreover, these strains can produce emetic toxin in room temperature. Therefore, the temperature control of milk-tea would be one of the key factors to decrease the risk of Bacillus cereus emetic toxin outbreak.