Characterization of ThreeBacillus cereusStrains Involved in a Major Outbreak of Food Poisoning After Consumption of Fermented Black Beans (Douchi) in Yunan, China

Abstract

Three Bacillus cereus strains isolated from an outbreak of food poisoning caused by the consumption of fermented black beans (douchi) containing B. cereus is described. The outbreak involved 139 persons who had nausea, vomiting, and diarrhea. The strains were isolated from vomit and the unprepared douchi. Two of the strains produced the emetic toxin cereulide, as evidenced by polymerase chain reaction analysis for the presence of the nonribosomal synthetase cluster responsible for the synthesis of cereulide and by chemical analysis by high-performance liquid chromatography-mass spectrometry. These two strains belong to genetic group III of B. cereus, and multiple locus sequence typing revealed that the type was ST26, as a major part of B. cereus emetic strains. One of these strains produced significantly more cereulide at 37°C than the type cereulide producer (F4810/72), and it was also able to produce the toxin at 40°C and 42°C. The third strain belongs to genetic group IV, and it is a new multiple locus sequence type closely related to strains that are cytotoxic and enterotoxigenic. It possesses genes for hemolysin BL, nonhemolytic enterotoxin, and cytotoxin K2; however, it varies from the majority of strains possessing genes for hemolysin BL by not being hemolytic. Thus, two B. cereus strains producing the emetic toxin cereulide and a strain producing enterotoxins might have been involved in this food-poisoning incident caused by the consumption of a natural fermented food. The ability of one of the strains to produce cereulide at ≥37°C makes it possible that it is produced in the human gut in addition to occurring in the food.

Identification of key micro-organisms involved in Douchi fermentation by statistical analysis and their use in an experimental fermentation

“…A major outbreak of food poisoning caused by the consumption of Douchi containing Bacillus cereus was also reported (Zhou et al . ). How to control the pathogens involved in Douchi fermentation process is the crux to ensure the fermented soybean food safety.…”

Bacillus cereus group: genetic aspects related to food safety and dairy processing

“…Furthermore, these authors found genetic similarity among an isolate obtained from a patient with others from strawberry butter and spinach cream using molecular methods, showing the importance of the use of distinct methodologies to investigate outbreaks. ZHOU et al (2014) reported another foodborne outbreak due to consumption of fermented black beans (Douchi) and showed the capacity of the strain to produce cereulide on temperatures higher than 37ºC, probably allowing toxin production on intestine and food. Although the illness caused by this bacterium is usually mild, sometimes it can cause death.…”

Destruction ofBacillus cereusspores in a thick soy bean paste (doenjang) by continuous ohmic heating with five sequential electrodes

“…Indeed, a B. cereus outbreak in China was attributed to fermented black beans ( doichi ), and 92 patients suffered severe nausea and vomiting (Zhou et al . ). When we examined commercial doenjang products manufactured by major companies in Korea, all contained B. cereus at 1·0–3·5 log CFU g −1 (Rhee et al .…”

“…Several studies have detected B. cereus in various soybean-based foods, including doenjang, sunsik (mixed grains and vegetable powder) and sufu (Chinese fermented soybeans) (Han et al 2001;Kim et al 2009a;Lee et al 2009). Indeed, a B. cereus outbreak in China was attributed to fermented black beans (doichi), and 92 patients suffered severe nausea and vomiting (Zhou et al 2014). When we examined commercial doenjang products manufactured by major companies in Korea, all contained B. cereus at 1Á0-3Á5 log CFU g À1 (Rhee et al 2011).…”