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.