Occurrence of Toxigenic Bacillus cereus and Bacillus thuringiensis in Doenjang, a Korean Fermented Soybean Paste (original) (raw)
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Detection of Enterotoxic Bacillus cereus and Bacillus thuringiensis Strains by PCR Analysis
Applied and Environmental Microbiology, 2001
Many strains of Bacillus cereus cause gastrointestinal diseases, and the closely related insect pathogen B. thuringiensis has also been involved in outbreaks of diarrhea. The diarrheal types of diseases are attributed to enterotoxins. Two different enterotoxic protein complexes, hemolysin BL (HBL) and nonhemolytic enterotoxin (NHE), and an enterotoxic protein, enterotoxin T, have been characterized, and the genes have been sequenced. PCR primers for the detection of these genes were deduced and used to detect the genes in 22 B. cereus and 41 B. thuringiensis strains. At least one gene of each of the two protein complexes HBL and NHE was detected in all of the B. thuringiensis strains, while six B. cereus strains were devoid of all three HBL genes, three lacked at least two of the three NHE genes, and one lacked all three. Five different sets of primers were used for detection of the gene (bceT) encoding enterotoxin T. The results obtained with these primer sets indicate that bceT is widely distributed among B. cereus and B. thuringiensis strains and that the gene varies in sequence among different strains. PCR with the two primer sets BCET1-BCET3 and BCET1-BCET4 unambiguously detected the bceT gene, as confirmed by Southern analysis. The occurrence of the genes within the two complexes is significantly associated, while neither the occurrence of the two complexes nor the occurrence of the bceT gene is significantly associated in the 63 strains. We suggest an approach for detection of enterotoxinencoding genes in B. cereus and B. thuringiensis based on PCR analysis with the six primer sets for the detection of genes in the HBL and NHE operons and with the BCET1, BCET3, and BCET4 primers for the detection of bceT. PCR analysis of the 16S-23S rRNA gene internal transcribed spacer region revealed identical patterns for all strains studied.
Detection of toxigenic Bacillus cereus and Bacillus thuringiensis spores in U.S. rice
International Journal of Food Microbiology, 2009
Bacillus cereus is a gram-positive, endospore forming pathogenic bacterium that is ubiquitous in the environment and is frequently associated with emetic and diarrheal types of foodborne illness. In this study, 178 samples of raw rice from retail food stores were analyzed for the presence of B. cereus spores. Spores of Bacillus species were found in 94 (52.8%) of the rice samples with an average concentration of 32.6 CFU/g (3.6-460 CFU/g for B. cereus and 3.6-23 CFU/g for Bacillus thuringiensis). Eighty three of the 94 isolates were identified as B. cereus and 11 were identified as B. thuringiensis. Bacillus mycoides (240 CFU/g) was the predominant isolate in one rice sample. Using PCR the isolates were checked for the presence of the cereulide synthetase gene (ces), the hblA and hblD genes of the hemolysin BL (HBL) complex and the nheA and nheB genes of the nonhemolytic (NHE) enterotoxin complex. The ces gene was not identified in any of the isolates. By contrast 47 (56.6%) B. cereus isolates possessed the hblA and hblD genes and 74 (89.1%) isolates possessed the nheA and nheB genes. As determined by commercial assay kits, forty four (53.0%) of the 83 B. cereus isolates produced both NHE and HBL enterotoxins whereas 78 (93.9%) were positive for either one or the other. Protein toxin crystals were detected visually in the 11 B. thuringiensis isolates. PCR analysis revealed 10 (90.9%) of those 11 isolates carried the cry gene. All the B. thuringiensis isolates were positive for NHE and HBL enterotoxins. Our results suggest that foodborne illness in the U.S. due to B. cereus with rice as the vehicle would be most likely associated with the diarrheal-type syndrome.
Enterotoxin Production of Bacillus thuringiensis Isolates From Biopesticides, Foods, and Outbreaks
Frontiers in Microbiology
While the relevance of Bacillus (B.) cereus as a major cause of gastroenteritis is undisputed, the role of the closely related B. thuringiensis in foodborne disease is unclear. B. thuringiensis strains frequently harbor enterotoxin genes. However, the organism has only very rarely been associated with foodborne outbreaks, possibly due to the fact that during outbreak investigations, B. cereus is routinely not differentiated from B. thuringiensis. A recent EFSA scientific opinion stresses the urgent need for further data allowing for improved risk assessment, in particular as B. thuringiensis is a commonly used biopesticide. Therefore, the aim of this study was to gain further insights into the hazardous potential of B. thuringiensis. To this end, 39 B. thuringiensis isolates obtained from commercially used biopesticides, various food sources, as well as from foodborne outbreaks were characterized by panC typing, panC-based SplitsTree analysis, toxin gene profiling, FTIR spectroscopic analysis, a cytotoxicity assay screening for enterotoxic activity, and a sphingomyelinase assay. The majority of the tested B. thuringiensis isolates exhibited low (23%, n = 9) or mid level enterotoxicity (74%, n = 29), and produced either no (59%, n = 23) or low levels (33%, n = 13) of sphingomyelinase, which is reported to act synergistically with enterotoxins Nhe and Hbl. One strain isolated from rosemary was however classified as highly enterotoxic surpassing the cytotoxic activity of the high-level reference strain by a factor of 1.5. This strain also produced vast amounts of sphingomyelinase. Combining all results obtained in this study into a fingerprint pattern, several enterotoxic biopesticide strains were indistinguishable from those of isolates from foods or collected in association with outbreaks. Our study shows that many B. thuringiensis biopesticide strains exhibit mid-level cytotoxicity in a Vero cell assay and that some of these strains cannot be differentiated from isolates collected from foods or in association with outbreaks. Thus, we demonstrate that the use of B. thuringiensis strains as biopesticides can represent a food safety risk, underpinning the importance of assessing the hazardous potential of each strain and formulation used.
Occurrence and significance of Bacillus cereus and Bacillus thuringiensis in ready-to-eat food
FEMS Microbiology Letters, 2005
Among 48,901 samples of ready-to-eat food products at the Danish retail market, 0.5% had counts of Bacillus cereus-like bacteria above 10 4 cfu g À1 . The high counts were most frequently found in starchy, cooked products, but also in fresh cucumbers and tomatoes. Forty randomly selected strains had at least one gene or component involved in human diarrhoeal disease, while emetic toxin was related to only one B. cereus strain. A new observation was that 31 out of the 40 randomly selected B. cereus-like strains could be classified as Bacillus thuringiensis due to crystal production and/or content of cry genes. Thus, a large proportion of the B. cereuslike organisms present in food may belong to B. thuringiensis.
Common occurrence of enterotoxin genes and enterotoxicity in Bacillus thuringiensis
FEMS Microbiology Letters, 2000
Seventy-four strains of Bacillus thuringiensis representing 24 serovars were examined for the presence of three enterotoxin genes/operons; the non-haemolytic enterotoxin Nhe, the haemolytic enterotoxin hbl and the Bacillus cereus toxin bceT using polymerase chain reaction. The nheBC genes were found in all strains examined, the hblCD genes in 65 of the 74 strains and bceT in 63 strains. There was little consistency of the distribution of enterotoxin loci among strains of the same serovar in serovars that were well represented in our collection. Culture supernatants from all but one strain inhibited protein synthesis in Vero cells, generally with a toxicity equivalent to that seen in strains of B. cereus isolated from incidents of food poisoning. ß 2000 Published by Elsevier Science B.V. on behalf of the Federation of European Microbiological Societies.
Bacillus cereus and Bacillus thuringiensis in ready-to-eat cooked rice in Malaysia
Bacillus cereus (B. cereus) isolates are toxigenic and can cause food poisoning. Cooked rice is a potentially hazardous food, especially in tropical countries. The aim of this study was to determine the prevalence of B. cereus and B. thuringiensis in raw and cooked rice marketed in Selangor, Malaysia. A combination of Most Probable Number-Polymerase Chain Reaction (MPN-PCR) method was used to detect gyrB gene in B. cereus and B. thuringiensis. Five local varieties of raw rice samples were negative for B. thuringiensis but all (100%) were positive for B. cereus. A total of 115 cooked rice samples (nasi lemak, nasi briyani, nasi ayam and nasi putih) were studied for the presence of B. cereus and B. thuringiensis. Nasi ayam was found to have the highest prevalence (100%) of B. cereus compared to nasi putih (76.2%) and nasi lemak (70.4%). Nasi briyani had the lowest prevalence (50%) of B. cereus. The frequencies of B. thuringiensis were found to be 10, 30 and 35.2 % in nasi putih and nasi ayam, nasi briyani and nasi lemak, respectively. Occurrence of B. cereus and B. thuringiensis in the samples ranged from < 3 to 1100 MPN/g in different samples. Maximum number of B. cereus was observed in nasi lemak, nasi briyani and nasi putih (> 1100 MPN/g) while nasi ayam showed less contamination (460 MPN/g) with B. cereus which was significantly different (P < 0.05) from others. The number of B. thuringiensis in nasi lemak, nasi briyani, nasi putih and nasi ayam were found to be >1100, 93, 9.2 and 3.6 MPN/g, respectively.
EFSA Journal, 2016
The minutes of the 9 th Working Group meeting held on 15 April 2016 were agreed. 3 5. Scientific topic(s) for discussion 5.1. Risks for public health related to the presence of Bacillus cereus and other Bacillus spp. including Bacillus thuringiensis in foodstuffs 4 The WG discussed the feedback from the BIOHAZ Panel on the draft opinion as well as the comments received from Ingvar Sundh who was nominated by PRAs Unit to review this draft opinion. All contributions received since the previous meeting were reviewed carefully. Tasks were allocated to EFSA staff and the WG Members.