• Title/Summary/Keyword: B. cereus

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Prevalence of Bacillus cereus Group in Rice and Distribution of Enterotoxin Genes

  • Jang, Ji-Hyun;Lee, No-A;Woo, Gun-Jo;Park, Jong-Hyun
    • Food Science and Biotechnology
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    • v.15 no.2
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    • pp.232-237
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    • 2006
  • Bacillus cereus group comprising B. cereus, B. thuringiensis, and B. mycoides was differentiated by polymerase chain reaction (PCR) and colony morphology. Prevalence of B. cereus group in rice and distribution of enterotoxin genes were determined as possible food poisoning agents. PCR using primers targeted for gyrB and cry genes could distinguish B. thuringiensis from B. cereus, and B. mycoides was differentiated by rhizoid morphological characteristics on nutrient agar. Among 136 rice and their processed products, prevalence of B. cereus group was 40%. B. cereus group consisted of 54 B. cereus, 11 B. thuringiensis, and 1 B. mycoides. Major isolates were B. cereus, with B. thuringiensis detected up to 10% among edible rice tested. Five enterotoxin genes, hbl, nhe, bceT, entFM, and cytK, were broadly distributed among B. cereus group, especially in B. cereus and B. thuringiensis. Prevalence of B. cereus group in rice and enterotoxin distribution suggest B. thuringiensis and B. cereus are toxigenic strain that should be controlled in rice and its products.

Reevaluation of Enumeration of Bacillus cereus Grown on Mannitol-Egg York-Polymyxin B Agar (Mannitol-Egg York-Polymyxin B 선택 배지에서 Bacillus cereus 계수 방법의 재평가)

  • Yun, Suk-Hyun;Kim, Yong-Sang;Jeong, Do-Yeon;Hahn, Kum-Su;Uhm, Tai-Boong
    • Korean Journal of Microbiology
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    • v.45 no.2
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    • pp.208-214
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    • 2009
  • To avoid ambiguity in counting the number of colony, about 1,500 of colonies grown on B. cereus selective agar plates were grouped into 12 types by morphological difference and then identified by biochemical and 16S rDNA nucleotide sequence. Among them, seven colony types with 11 to 15 mm diameters of halo were identified as B. cereus or B. cereus subsp. cytotoxis. Five mm sized colonies with no halo, which have not been considered as B. cereus according to the manufacturer's manual, were identified as B. cereus. A colony type with double halos of only 6 mm in diameter was also B. cereus. Other three types were proven to be Enterococcus sp., Brevibacillus sp., and B. subtilis, respectively. PCR results showed that only 9 types that are identified as B. cereus strains harbor at least one of B. cereus toxin genes.

Detection of Emetic Bacillus cereus from Ready-to-eat Foods in Markets and its Production of Cereulide under Simulated Conditions

  • Kim, Heesun;Chang, Hyeja
    • Journal of the FoodService Safety
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    • v.1 no.1
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    • pp.9-18
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    • 2020
  • B. cereus-produced cereulide as an emetic toxin is commonly isolated in starch-based cooked foods. This study examined the prevalence of B. cereus from ready-to-eat foods in markets by polymerase chain reaction analysis and determined the relationship between the level of B. cereus and the quantity of cereulide in the sample after different storage times and temperatures. The prevalence of general B. cereus in 43 starch foods was 32.6%, and the level of B. cereus ranged from 0.5 to 1.95 log cfu/g, meeting the Korea Food Code Specifications of 3 log CFU/g of B. cereus. No samples revealed emetic B. cereus. Fried rice samples were inoculated with a cereulide-producing reference strain, B. cereus NCCP 14796, to determine the level of B. cereus and the quantity of cereulide in the samples after storage for 0, 4, 6, 8, 20, 24, 30, 48, 72, and 96 h at 7, 25, 35, and 57℃. The average levels of B. cereus at 7, 25, 35, and 57℃ were 4.38, 7.31, 7.88, and 3.82 log cfu/g, and the levels of cereulide were 150.41, 1680.70, 2652.65, and 77.83 ㎍/mL, respectively, showing a significant difference according to the incubation time (P<0.05) and temperature (P<0.001).

Inhibition of Bacillus cereus Growth and Toxin Production by Bacillus amyloliquefaciens RD7-7 in Fermented Soybean Products

  • Eom, Jeong Seon;Choi, Hye Sun
    • Journal of Microbiology and Biotechnology
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    • v.26 no.1
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    • pp.44-55
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    • 2016
  • Bacillus cereus is a gram-positive, rod-shaped, spore-forming bacterium that has been isolated from contaminated fermented soybean food products and from the environment. B. cereus produces diarrheal and emetic toxins and has caused many outbreaks of foodborne diseases. In this study, we investigated whether B. amyloliquefaciens RD7-7, isolated from rice doenjang (Korean fermented soybean paste), a traditional Korean fermented soybean food, shows antimicrobial activity against B. cereus and regulates its toxin gene expression. B. amyloliquefaciens RD7-7 exhibited strong antibacterial activity against B. cereus and inhibited the expression of B. cereus toxin-related genes (groEL, nheA, nheC, and entFM). We also found that addition of water extracts of soybean and buckwheat soksungjang (Korean fermented soybean paste made in a short time) fermented with B. amyloliquefaciens RD7-7 significantly reduced the growth and toxin expression of B. cereus. These results indicate that B. amyloliquefaciens RD7-7 could be used to control B. cereus growth and toxin production in the fermented soybean food industry. Our findings also provide a basis for the development of candidate biological control agents against B. cereus to improve the safety of fermented soybean food products.

Molecular Cloning of Chitosanase Gene and Quantitative Production of Chitosan Oligomer (키토사네이즈 유전자의 클로닝과 키토산 올리고머의 정량적 생산)

  • 박유미;장혜란;허태린;김사열
    • Microbiology and Biotechnology Letters
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    • v.32 no.1
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    • pp.16-21
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    • 2004
  • Six bacterial strains which formed large halo on chitosan-containing agar plate were isolated from beach mud and crabs at South coast of Korean peninsula. They were designated as Bacillus cereus KNUC51, B. cereus KNUC52, B. cereus KNUC53, B. cereus KNUC54, B. cereus KNUC55, and Paenibacillus favisporus KNUC56 by analysing their morphologies and 16S rDNA sequences. Chitosanase activities of all isolates were similar to that of B. subtilis 168. To enhance the activity of chitosanase, a powerful mutagen, MNNG was treated for P favisporus KNUC56. Three mutants showed higher activity of chitosanase than that of the original strain. The DNA fragments containing chitosanase gene from B. cereus sources were cloned, sequenced, and their deduced amino acid sequence analysis showed over 93% homologies with that of the known B. cereus ATCC14579. Extracellular sample from the isolates was incubated in proper reaction mixture including chitosan for 5 minutes at $37^{\circ}C$ to produce 3-10 chitosan oligomers which has been known to be active for clinical agents and agronomical agents.

Development and Validation of Predictive Model for Foodborne Pathogens in Preprocessed Namuls and Wild Root Vegetables (전처리 나물류 및 구근류에서 병원성 미생물의 성장예측모델 개발 및 검증)

  • Enkhjargal, Lkhagvasarnai;Min, Kyung Jin;Yoon, Ki Sun
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.42 no.10
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    • pp.1690-1700
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    • 2013
  • The objective of this study is to develop and validate predictive growth models for Bacillus cereus (diarrhea type) vegetative cells, spores and Staphylococcus aureus in preprocessed Namul (bracken and Chwinamul) and root vegetables (bellflower and burdock). For validation of model performance, growth data for S. aureus in preprocessed vegetables were collected at independent temperatures (18 and $30^{\circ}C$) not used in the model development. In addition, model performance of B. cereus (diarrhea type) in preprocessed vegetables was validated with an emetic type of B. cereus strain. In primary models, the specific growth rate (SGR) of the B. cereus spores was faster than that of the B. cereus vegetative cells, regardless of the kinds of vegetables at 24 and $35^{\circ}C$, while lag time (LT) of the B. cereus spores was longer than that of the B. cereus vegetative cells, except for burdock. The growth of B. cereus and S. aureus was not observed in bracken at temperatures lower than 13 and $8^{\circ}C$, respectively. The LT models for B. cereus (diarrhea type) in this study were suitable in predicting the growth of B. cereus (emetic type) on burdock and Chwinamul. On the other hand, SGR models for B. cereus (diarrhea type) were suitable for predicting the growth of B. cereus (emetic type) on all preprocessed vegetables. The developed models can be used to predict the risk of B. cereus and S. aureus in preprocessed Namul and root vegetables at the retail markets.

Identification Based on Computational Analysis of rpoB Sequence of Bacillus anthracis and Closely Related Species (Bacillus anthracis와 그 유연종의 rpoB 유전자 컴퓨터 분석을 통한 동정)

  • Kim, Kyu-Kwang;Kim, Han-Bok
    • Korean Journal of Microbiology
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    • v.44 no.4
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    • pp.333-338
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    • 2008
  • Computational analysis of partial rpoB gene sequence (777 bp) was done in this study to identify B. anthracis and its closely related species B. cereus and B. thuringiensis. Sequence data including 17 B. anthracis strains, 9 B. cereus strains, and 7 B. thuringiensis strains were obtained by searching databases. Those sequences were aligned and used for other computational analysis. B. anthracis strains were identificated by in silico restriction enzyme digestion. B. cereus and B. thuringiensis were not segregated by this method. Those sequencing and BLAST search were required to distinguish the two. In actual identification tests, B. anthracis strains could be identified by PCR-RFLP, and B. cereus and B. thuringiensis strains were distinguished by BLAST search with reliable e-value. In this study fast and accurate method for identifying three Bacillus species, and flow chart of identification were developed.

Discrimination of Bacillus anthracis from Bacillus cereus Group Using KHT5 Marker (KHT5 마커를 사용한 Bacillus cereus 그룹에서 Bacillus anthracis의 구별)

  • 김형태;김성주;채영규
    • Korean Journal of Microbiology
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    • v.39 no.1
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    • pp.40-44
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    • 2003
  • Bacillus anthracis is a gram-positive spore-forming bacterium that causes the disease anthrax. In order to develop a DNA marker specific for Bacillus anthracis and to discriminate this species from Bacillus cereus group, we applied the randomly amplified polymorphic DNA (RAPD)-PCR technique to a collection of 29 strains of the genus Bacillus, including 22 species of the B. cereus group. A 709-bp RAPD marker (KHT5) specific for B. anthracis was obtained from B. anthracis BAK. The PCR product of internal primer set from the KHT5 fragment distinguished B. anthracis from the other species of the B. cereus group.

Detection of $Bacillus$ $cereus$ Group from Raw Rice and Characteristics of Biofilm Formation (쌀로부터 $Bacillus$ $cereus$ Group의 분리와 Biofilm 형성 특성)

  • Kim, Jin-Young;Yoo, Hye-Lim;Lee, Young-Duck;Park, Jong-Hyun
    • The Korean Journal of Food And Nutrition
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    • v.24 no.4
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    • pp.657-663
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    • 2011
  • $Bacillus$ $cereus$ is widely distributed on various foods and is known to cause clinical infections, food poisoning toxin induced diarrhea and vomiting. In this study, $B.$ $cereus$ group detected and analyzed rice, rice bran, and biofilm characterization of $B.$ $cereus$ confirmed. $B.$ $cereus$ was identified in approximately 34.6% of brown rice and 50.0% of rice bran. $B.$ $thuringiensis$ was detected in 3.9% of brown rice and 23% of rice bran, and $B.$ $mycoides$ was isolated from rice bran. The microtiter plate assay detected differences in biofilm-forming ability among $B.$ $cereus$ group isolates. Biofilm of $B.$ $cereus$ seemed to increase the MIC values of antimicrobial agent and antibiotic compounds compared with planktonic cells. Therefore, sufficient attention should be given to good manufacturing practice and good agriculture practice to avoid contamination of $B.$ $cereus$ group raw material including rice.

Toxin Gene Analysis of Bacillus cereus and Bacillus thuringiensis Isolated from Cooked Rice (쌀밥에서 분리한 Bacillus cereus와 Bacillus thuringiensis의 독소유전자 분석)

  • Jeon, Jong-Hyuk;Park, Jong-Hyun
    • Korean Journal of Food Science and Technology
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    • v.42 no.3
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    • pp.361-367
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    • 2010
  • Bacterial contamination of cooked rice was analyzed to evaluate the microbial safety. Thirty raw rice samples were collected in Korea and cooked in an electric rice cooker. Mesophilic aerobe, food-poisoning Bacillus cereus group, and their toxin genes were determined on cooked rice. The percentage of total mesophilic aerobe based on 1-3 log CFU/g was 27% among the samples. Bacillus spp. in MYP selective medium was similar to the number of mesophilic aerobe, whileas Bacillus spp. was detected in most samples after enrichment. Thirty-seven isolates from 30 cooked rices were identified as B. thuringiensis, B. cereus, B. valismortis, B. pumilus, B. coagulans, B. licheniformis, Geobacillus stearothermophilus, and Brevibacillus laterosporus. Twenty isolates (54%), more than half of the isolates, were B. thuringiensis while nine (27%) were identified as B. cereus. All B. thuringiensis isolates possessed non-hemolytic toxin genes and interestingly, seven B. cereus among nine isolates possessed emetic toxin genes. More B. thuringiensis was present on the cooked rice than B. cereus and most B. cereus possessed emetic toxin genes rather than diarrheal toxin genes. Therefore, food-borne outbreak due to B.cereus on the cooked rice kept at room temperature might be examples of emetic food-poisoning.