Incidence and biochemical characteristics of Bacillus flora in Sardinian dairy products
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Keywords:
Cereus
Bacillus coagulans
Bacillus (shape)
1. REVIEW OF THE LITERATURE 1 1.1. Taxonomic view on B. cereus 1 1.1.1. B. cereus group 1 1.1.2. The species B. cereus (sensu stricto) 1 1.2. B. cereus spore 2 1.2.1. Ultrastructure of the Bacillus spore 2 1.2.2. Properties of the Bacillus spores and those of B. cereus spores 3 1.2.3. Sporulation and germination of Bacillus spores 5 1.3. Diversity of B. cereus 6 1.4. Interactions of B. cereus with living and nonliving environment 7 1.4.1. Adhesion of B. cereus to nonliving and living surfaces 7 1.4.2. Antagonistic property of B. cereus towards microorganisms 8 1.4.3. B. cereus as a probiotic 8 1.5. Human virulence 10 1.5.1. B. cereus as a human pathogen 10 1.5.2. Cereulide, the emetic toxin of B. cereus 11 1.5.2.1. Structure and properties of cereulide 11 1.5.2.2. Toxic mechanisms and detection of cereulide 13 1.5.2.3. Toxicity of cereulide in whole animals 14 2. AIMS OF THE STUDY 20 3. MATERIALS AND METHODS 21 4. RESULTS AND DISCUSSION 22 4.1. Strategies for isolating and identifying cereulide producers among strains and isolates of B. cereus 22 4.2. Cereulide productivity of B. cereus isolates of geographically and temporally diverse origins 23 4.3. Occurrence of cereulide producing B. cereus in some environmental niches ..24 4.4. Potential for cereulide production in selected infant food formulas 25 4.5. Strategies of B. cereus spores for persistence in the dairy process environment 33 4.6. Are the cereulide producing B. cereus successful in competition with the non producing B. cereus in food? 34 5. SUMMARY AND CONCLUSIONS 36 6. ACKNOWLEDGEMENTS 38 7. REFERENCES 39
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In cooked-chilled and pasteurized vegetable products, initial numbers of Bacillus cereus were below 10 cfu g−1. Before the appearance of spoilage, numbers reached 6–8 log cfu g−1 at 20 °C and 4–6 log cfu g−1 at 10 °C. Bacillus cereus was not detected in samples stored at 4 °C. Ten percent of strains isolated from the products were able to grow at 5 °C and 63% at 10 °C. Bacillus cereus strains unable to degrade starch, a feature linked to the production of emetic toxin, did not grow at 10 °C and had a higher heat resistance at 90 °C. Using immunochemical assays, enterotoxin was detected in the culture supernatant fluid of 97·5% of the strains. All culture supernatant fluids were cytotoxic but important variations in the level of activity were found. Psychrotrophic isolates of B. cereus were unable to grow in courgette broth at 7 °C whereas they grew in a rich laboratory medium. At 10 °C, these isolates grew in both media but lag time in courgette broth was 20-fold longer than in the rich laboratory medium.
Cereus
Pasteurization
Bacillaceae
Tryptic soy broth
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본 연구에서는 인터넷에서 판매되는 배달이유식의 위생안전성을 평가하고, B. cereus의 독소유전자 분포를 파악하여 즉석조리식품으로 구분되는 이유식의 B. cereus 기준설정을 위한 기초자료를 제공하고자 하였다. 기타 영 유아식 27건, 즉석조리식품 79건 등 총 106건에 대한 실험결과는 다음과 같다. 1. 이유식 106건의 세균수 검사결과 기타 영 유아식에서는 12건(44%)에서 최대 $2.5{\times}10^3CFU/g$ , 즉석조리식품에서는 46건(58%)에서 최대 $1.1{\times}10^6CFU/g$ 으로 대체적으로 즉석조리식품에서 세균수가 많이 검출되었다. 2. 106건의 검체 중 총 9건에서 B. cereus가 $10{\sim}3.6{\times}10^3CFU/g$ 범위로 검출되었으며 모두 즉석조리식품이었다. 3. B. cereus의 독소유전자 중 cytK는 6주(66.6%), nheA 및 entFM은 8주(88.9%), bceT는 7주(77.8%), hblC는 3주(33.3%)에서 검출되었으며 구토독소인 cer은 2주(22.2%)에서만 증폭밴드가 나타났다. 4. 분리된 균주는 B. cereus와 B. thuringiensis를 구분하기 위한 시험법에서 모두 B. cereus로 나타났다. Bacillus cereus is food poisoning bacteria frequently occured in starch food. Most of the delivery foods for infant is classified as ready-to-cook food. But unlike food for infant and young children, there are no standards and specifications of Bacillus cereus in ready-to-cook food. The purpose of this study is to examine the presence of Bacillus cereus, aerobic bacteria and coliforms in the food for infant and young children sold through internet. B. cereus was detected in 9 samples (8.3%), total aerobic bacteria was detected over $10^6CFU/g$ in 4 samples and coliforms were not detected in any samples. This will provide basic data for standards and specifications of Bacillus cereus in ready-to-cook food.
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Aerobic bacteria
Food poisoning
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Bacillus thuringiensis
Bacillaceae
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当院では2005年度に血液培養でBacillus cereusの増加傾向がみられた.血液培養でB. cereusが検出された患者の背景を調べた結果,大半の患者で末梢カテーテルを留置していた.さらに血液培養でB. cereusが検出された数名の患者の末梢カテーテル先端からもB. cereusが検出され,B. cereusによる血流感染ありと判断した.また文献的に検索するとB. cereus菌血症についてはリネン等の汚染や留置カテーテルの取り扱いが指摘されているが,カテーテルの汚染とリネンの汚染との結びつきについては不明な点が多い.そこで今回我々はカテーテルにおける菌の定着と増殖の原因について,輸液製剤の種類による菌の発育速度と温度の影響,環境因子の影響について調査を行ったので報告する.輸液製剤の種類や保管時間の影響に関しては,B. cereusがStaphylococcus aureusやStaphylococcus epidermidisと比較して増加しやすいという傾向が見られた.環境検査ではタオルの培養で≦102~1×106 cfu/mLのB. cereusが検出された.落下菌の測定では,一般環境より病室で多く検出される傾向が見られた.さらにリネンの出し入れ後の落下菌の検査を行うと短時間で多数のB. cereusが検出された.以上より輸液製剤の保管の影響よりも,薬剤の調合やカテーテルの刺入,ルート交換を行う環境や取り扱いに問題があると考えた.
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The sigB gene of Bacillus cereus ATCC 14579 encodes the alternative sigma factor sigma(B). Deletion of sigB in B. cereus leads to hyperresistance to hydrogen peroxide. The expression of katA, which encodes one of the catalases of B. cereus, is upregulated in the sigB deletion mutant, and this may contribute to the hydrogen peroxide-resistant phenotype.
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즉석섭취 편의식품은 일반적으로 소비자가 별도의 조리과정 없이 직접 신선한 상태로 섭취하기 때문에 병원성 미생물에 오염되어 있을 경우 식중독을 일으킬 수 있다. 특히 B. cereus는 자연계에 널리 분포하여 대부분의 식품에 쉽게 오염되어 식중독을 유발 시킬 수 있는 독소형 식중독균 중의 하나이다. 이에 본 연구는 유통 판매중인 즉석섭취 편의식품류 및 식중독이 발생하여 의뢰된 보존식에서 B. cereus의 분리율 및 독소 종류의 분포형태를 파악하였다. 식품 총 619건 중 263건(42.5%)의 B. cereus를 분리하였지만, 식품의약품안전처의 식품공전에서 즉석섭취 편의식품류에 대한 B. cereus에 대한 규격기준이 1,000 CFU/g 이하로, 본 실험에서는 규정 범위를 초과한 식품은 없었다. B. cereus 총 263개 분리균주에 대한 9종류의 장내독소 및 1종류의 구토독소를 분석한 결과, NHE complex (nheA, nheB, nheC)중 3개의 nhe 유전자를 모두 보유한 B. cereus는 236개 균주(89.7%), 1개만의 독소를 가지고 있는 균주는 2개(0.8%)뿐이었다. 또한, HBL complex (hblA, hblB, hblD) 중 3개의 hbl 유전자를 보유한 균주는 175개 균주(66.5%), 그리고 한개 혹은 두 개의 hbl 유전자를 가진 균주는 59개 균주(21.7%), 3개 유전자를 모두 가지고 있지 않은 균주는 29개 분리균주(11.0%)로 나타났다. NHE complex 유전자의 빈도가 HBL complex 유전자 보다 더 높게 나타나는 특징을 확인할 수 있었다. 장내독소 entFM, $cytK_2$ , bceT 유전자의 보유율은 각각 100, 100, 43.0% 순으로 확인되었다. B. cereus의 구토 독소인 CER 유전자는 평균 50.2%를 보유하고 있었으며, 식품유형에 따라 식중독 보존식, 즉석섭취 식품, 편의식품에서 각각 100, 59.4, 35.6% 순으로 나타났다. 식품 중 분리한 B. cereus가 산생하는 구토독소를 가지고 있는 B. cereus 균주 중 29.4%에서 8개의 장내독소를 보유하고 있었으며, 나머지 균주들도 대부분 5-8개의 장내독소를 가지고 있는 것으로 확인되었다. 따라서 본 연구 결과를 종합해보면, 식품에서 분리한 B. cereus는 대부분의 균주가 설사형 및 구토형 독소를 보유하고 있어, 즉석 섭취 편의식품의 미생물 오염 요인들은 계절에 관계없이 지속적으로 위생적인 관리가 필요할 것으로 사료된다. 또한, 식품의 미생물적 안전성 확보를 위해서는 업체의 생산단계부터 저장 및 운반을 포함한 유통단계 등에서 식중독을 유발 할 수 있는 오염원들이 내재되어 있기 때문에 철저한 개인 및 환경 위생관리가 필요할 것으로 사료된다. Toxin-producing Bacillus cereus is the causative agent of two different types of food poisoning: the emetic and the diarrheal types. This study was conducted to investigate the presence of enterotoxin and emetic toxin genes in 263 B. cereus isolated from 619 different ready-to-eat food items. Hemolytic enterotoxins hblA, hblC, and hblD were detected in 85.6, 41.1, and 76.8%, respectively, of the B. cereus isolates. About 67.0% (175/263) of the isolates presented all of three genes. Non-hemolytic enterotoxins nheA, nheB, and nheC were detected in 100, 97.0, and 68.4% of the isolates, respectively. Approximately 90.0% (236/263) of the isolates presented all of these three non-hemolytic enterotoxin genes. Emetic toxin gene, CER, was detected in 132 of 263 (50.2%) isolates. Computer-assisted cluster analysis of Rep-PCR profiles showed a high genetic diversity among the isolates. All B. cereus isolates from food samples tested in this study carried at least 6 of 10 toxin genes.
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Food poisoning
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Geobacillus stearothermophilus
Bacillaceae
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Food poisoning
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Aims: This study identified and studied the response of five Bacillus strains, isolated from alkaline cleaning in place (CIP) solutions, to alkaline conditions. Methods and Results: Isolates were identified as B. cereus by 16S rDNA sequencing. External and internal cell pH and buffering capacity data of a representative strain, Bacillus DL5, were compared to B. cereus ATCC 10702. Results indicated that a buffering system was induced when the pH of the growth medium increased to above pH 10, which was effective up to pH 12 and presumably cell wall associated. Volume measurements and confocal scanning laser microscope images of Bacillus DL5 cells showed that cells exhibited more pronounced stress symptoms when exposed to pH 10 than at pHs above 10. Long-term exposure of Bacillus DL5 to pH 10 or 10·5 indicated that cells grew in planktonic form and formed biofilms at both pHs. Conclusions: Bacillus DL5 was a neutrophile with a growth pH range similar to B. cereus ATCC 10702, but tolerated alkaline pH. This may be a general trait of the B. cereus species rather than a specific phenomenon of isolates from alkaline ecosystems. Significance and Impact of the Study: Other neutrophilic B. cereus isolates may exhibit similar responses to alkaline conditions as the isolates studied here. These results may have important implications for dairy manufacturers.
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Bacillaceae
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