蜡样芽胞杆菌致肠炎

临床上蜡样芽胞杆菌致肠炎并没有受重视。临床怀疑痢疾患者，在非传染病医院多为抗菌素治疗，补液之后介绍转入传染病院治疗。几乎不做菌培养。 患者，男，72岁。前一天晚腹泻10余次，次日早入院。体温38.5℃。血常规 WBC 22.0×109/L，N 0.87 L 0.11 M 0.02。便常规黄色稀样便，每高倍镜视野WBC 4~6个 RBC 6~8个 EC 2~4个，潜血++。与痢疾症状相似。细菌鉴定：取便标本立即接种血琼脂和麦康凯平皿上，37℃培养24h；血平皿上生成的菌落灰绿色，边缘不齐，周围有溶血圈，直径1.0~1.5mm；麦康凯平皿上生成菌落周边乳白色中间为粉红色…     

一起蜡样芽胞杆菌食物中毒的调查

1992年7月11日，驻辽西某部五连发生一起食物中毒，就餐66人，发病27人，发病率为40．9％。经流行病学调查及实验室检验证明．为一起由蜡样芽胞杆菌引起的食物中毒。     

一起蜡样芽胞杆菌所致食物中毒

1998年10月22日,某宾馆职工在集体食堂就餐后,发生食物中毒,经调查及实验证明系食用蜡样芽胞杆菌污染的米饭所致。1．流行病学调查1998年10月22日1：30分,该宾馆集体食堂进餐后30min即出现急性消化道症状首例病人,至当天下午6时左右就餐对人中42人发病,发病率89．36％,其中5人因症状较重住院治疗。现场调查表明,发病42人均食用米饭,末发病5人只食用莱而未吃食堂所售米饭。患者中最大年龄42岁,最小8岁,男性7人,女性35人。2．临床表现2．l潜伏期：最短30min,最长sh,中位数为2．3h。2．2临床症状：以胃肠道症状为主,症状较轻。…     

一起蜡样芽胞杆菌食物中毒的调查报告

２００１年４月１０日,湛江市某小学发生一起食物中毒,现将调查结果报告如下：１ 流行病学调查１．１ 中毒经过：２００１年４月１０日上午,湛江市某小学师生进食由某面包厂供应的早餐,用餐人数８４２人。当餐食谱有豆浆、肠粉、酥饼。进食半小时后有进食者发病,进食４小时终止新病例发生,共有２５人发生中毒。经调查询问２５例发病人员均进食了肠粉,而进食肠粉共２１０人,患病率１１．９％,设有进食肠粉的其他同餐进食人员未发病。１．２ 卫生学调查：某面包厂供应给湛江市某小学的早餐,其豆浆、酥饼是该厂加工制作,而肠粉则由…     

一起蜡样芽胞杆菌引起的食物中毒调查

目的探讨一起食物中毒的流行因素及病原学。方法按流行病学现场调查方法,结合临床表现和实验室细菌学鉴定方法。结果就餐人数为150例,中毒病人108例,罹患率72%;临床表现以呕吐为主;中毒食物为隔夜剩饭,病原学检查为蜡样芽孢杆菌,中毒食物中蜡样芽孢杆菌菌落为1.2×106/g。结论此次食物中毒事件是由蜡样芽胞杆菌引起,此类食物中毒应引起人们的关注。     

一起蜡样芽胞杆菌引起的学生食物中毒

目的 为了了解蜡样芽胞杆菌引起的食物中毒的特点,增强学生食堂操作人员卫生意识,减少类似中毒事件发生.方法 采用染色法、培养基和试剂,根据GB/T4789.28-2003《食品卫生微生物学检验标准》.结果 经实验室检验,在剩米饭和患者呕吐物同时检出一种优势菌,该菌为G+粗大杆菌,在液体培养基中生长混浊,在琼脂培养基上生长为不透明菌落,表面粗糙似融蜡状,边缘不齐;过氧化氢酶试验阳性,半固体表面有动力,甘露醇细菌计数为1.08 ×106个/g.结论 通过实验室检验,表明该次食物中毒为蜡样芽胞杆菌所致.监督部门应该加强食品卫生知识的培训,加强卫生工作的经常性监督,督促操作人员养成良好的卫生习惯,减少类似食物中毒事件的发生.     

蜡样芽胞杆菌感染性眼内炎细菌培养分析

目的:研究蜡样芽胞杆菌感染眼内炎的细菌学特性。方法:采用K-B纸片法,NCCLS标准判断结果。结果:蜡样芽胞杆菌对氨苄西林、头孢菌素耐药,但对万古霉素、庆大霉素、妥布霉素、左氟沙星、氧氟沙星、洛美沙星、环丙沙星等抗菌药物敏感。结论:了解细菌特性和敏感性可对眼内炎的预防和治疗提供依据。     

蜡样芽胞杆菌食品中污染情况调查

为了解我市蜡样芽胞杆菌在食品中污染分布情况，预防食物中毒事件的发生。于2000年8月对常见相关食品进行了调查，现将结果报道如下。     

一起由蜡样芽胞杆菌引起的食物中毒调查分析

2002年10月1日，下洋镇某电子厂食堂发生了一起食物中毒，根据流行病学调查、临床症状、实验室检验结果，确认该食物中毒由蜡样芽胞杆菌引起，现将调查及检验情况报道如下。     

一起蜡样芽胞杆菌引起的学生食物中毒调查分析

蜡样芽孢杆菌是食物中毒中较常见的致病菌,蜡样芽胞杆菌引起的食物中毒,近几年来在我省较为多见,引起食物中毒所涉及的食品种类较多,多以剩米饭、米粉最为常见,本文就一     

The Crystal Structure of Bacillus cereus HblL1

The Hbl toxin is a three-component haemolytic complex produced by Bacillus cereus sensu lato strains and implicated as a cause of diarrhoea in B. cereus food poisoning. While the structure of the HblB component of this toxin is known, the structures of the other components are unresolved. Here, we describe the expression of the recombinant HblL₁ component and the elucidation of its structure to 1.36 Å. Like HblB, it is a member of the alpha-helical pore-forming toxin family. In comparison to other members of this group, it has an extended hydrophobic beta tongue region that may be involved in pore formation. Molecular docking was used to predict possible interactions between HblL₁ and HblB, and suggests a head to tail dimer might form, burying the HblL₁ beta tongue region.     

The Pore-Forming Hemolysin BL Enterotoxin from Bacillus cereus: Subunit Interactions in Cell-Free Systems

The tripartite enterotoxin Hemolysin BL (Hbl) has been widely characterized as a hemolytic and cytotoxic virulence factor involved in foodborne diarrheal illness caused by Bacillus cereus. Previous studies have described the formation of the Hbl complex and aimed to identify the toxin’s mode of action. In this study, we analyzed the assembly of Hbl out of its three individual subunits L₁, L₂ and B in a soluble as well as a putative membrane bound composition using a Chinese hamster ovary (CHO) cell-free system. Subunits were either coexpressed or synthesized individually in separate cell-free reactions and mixed together afterwards. Hemolytic activity of cell-free synthesized subunits was demonstrated on 5% sheep blood agar and identified both synthesis procedures, coexpression as well as individual synthesis of each subunit, as functional for the synthesis of an active Hbl complex. Hbl’s ability to perforate cell membranes was evaluated using a propidium iodide uptake assay. These data suggested that coexpressed Hbl subunits augmented cytotoxic activity with increasing concentrations. Further, a pre-pore-complex of L₁-L₂ showed cytotoxic effects suggesting the possibility of an interaction between the cell membrane and the pre-pore-complex. Overall, this study shows that cell-free protein synthesis is a fast and efficient way to study the assembly of multiple protein subunits in soluble as well as vesicular fractions.     

Multifaceted toxin profile,an approach toward a better understanding of probiotic Bacillus cereus

Abstract

Strains of the Bacillus cereus group have been widely used as probiotics for human beings, food animals, plants, and environmental remediation. Paradoxically, B. cereus is responsible for both gastrointestinal and nongastrointestinal syndromes and represents an important opportunistic food-borne pathogen. Toxicity assessment is a fundamental issue to evaluate safety of probiotics. Here, we summarize the state of our current knowledge about the toxins of B. cereus sensu lato to be considered for safety assessment of probiotic candidates. Surfactin-like emetic toxin (cereulide) and various enterotoxins including nonhemolytic enterotoxin, hemolysin BL, and cytotoxin K are responsible for food poisoning outbreaks characterized by emesis and diarrhea. In addition, other factors, such as hemolysin II, Certhrax, immune inhibitor A1, and sphingomyelinase, contribute to toxicity and overall virulence of B. cereus.     

Enterotoxin Gene Distribution and Genotypes of Bacillus cereus sensu lato Isolated from Cassava Starch

Bacillus cereus is a human pathogenic bacterium found in foods with the potential to cause emesis and diarrhea. This study estimated the presence, toxigenic and genomic diversity of B. cereus s.l. obtained from cassava starch samples collected in bakeries and powdered food companies in Medellín (Colombia). Bacillus cereus s.l. was found in 43 of 75 (57%) cassava starch samples and 98 isolates were obtained. The nheABC, hblCDAB, cytK2, entFM and cesB toxin genes were detected by multiplex PCR and the most frequent operon was nheABC, whereas cesB gene was not found. Twelve toxigenic profiles were determined by the detection of toxin genes, and the most frequent profiles harbored all enterotoxin genes. A broad genomic diversity was detected according to GTG₅-PCR fingerprinting results with 76 B. cereus s.l. grouped in sixteen clusters and the 22 isolates clustering separately. No relationship was observed between genomic background and toxigenic profiles. In general, the results showed a high genomic and enterotoxigenic diversity in B. cereus s.l. found in cassava starch. These results should incentive future studies to understand the distribution of B. cereus s.l. isolated on raw materials in comparison with finished products.     

Bacillus cereus Induces Severe Infections in Preterm Neonates: Implication at the Hospital and Human Milk Bank Level

Human breast milk (HBM) is a source of essential nutrients for infants and is particularly recommended for preterm neonates when their own mother’s milk is not available. It provides protection against infections and decreases necrotizing enterocolitis and cardiovascular diseases. Nevertheless, HBM spoilage can occur due to contamination by pathogens, and the risk of a shortage of HBM is very often present. B. cereus is the most frequent ubiquitous bacteria responsible for HBM being discarded. It can contaminate HBM at all stages, from its collect point to the storage and delivery. B. cereus can induce severe infection in newborns with very low birth weight, with sometimes fatal outcomes. Although the source of contamination is rarely identified, in some cases, HBM was suspected as a potential source. Even if the risk is low, as infection due to B. cereus in preterm infants should not be overlooked, human milk banks follow strict procedures to avoid contamination, to accurately identify remaining bacteria following pasteurization and to discard non-compliant milk samples. In this review, we present a literature overview of B. cereus infections reported in neonates and the suspected sources of contamination. We highlight the procedures followed by the human milk banks from the collection of the milk to its microbiological characterization in Europe. We also present improved detection and decontamination methods that might help to decrease the risk and to preserve the public’s confidence in this vital biological product for infants whose mothers cannot breastfeed.     

Detection of Enterotoxigenic Psychrotrophic Presumptive Bacillus cereus and Cereulide Producers in Food Products and Ingredients

In the last decade, foodborne outbreaks and individual cases caused by bacterial toxins showed an increasing trend. The major contributors are enterotoxins and cereulide produced by Bacillus cereus, which can cause a diarrheal and emetic form of the disease, respectively. These diseases usually induce relatively mild symptoms; however, fatal cases have been reported. With the aim to detected potential toxin producers that are able to grow at refrigerator temperatures and subsequently produce cereulide, we screened the prevalence of enterotoxin and cereulide toxin gene carriers and the psychrotrophic capacity of presumptive B. cereus obtained from 250 food products (cereal products, including rice and seeds/pulses, dairy-based products, dried vegetables, mixed food, herbs, and spices). Of tested food products, 226/250 (90.4%) contained presumptive B. cereus, which communities were further tested for the presence of nheA, hblA, cytK-1, and ces genes. Food products were mainly contaminated with the nheA B. cereus carriers (77.9%), followed by hblA (64.8%), ces (23.2%), and cytK-1 (4.4%). Toxigenic B. cereus communities were further subjected to refrigerated (4 and 7 °C) and mild abuse temperatures (10 °C). Overall, 77% (94/121), 86% (104/121), and 100% (121/121) were able to grow at 4, 7, and 10 °C, respectively. Enterotoxin and cereulide potential producers were detected in 81% of psychrotrophic presumptive B. cereus. Toxin encoding genes nheA, hblA, and ces gene were found in 77.2, 55, and 11.7% of tested samples, respectively. None of the psychrotrophic presumptive B. cereus were carriers of the cytotoxin K-1 encoding gene (cytK-1). Nearly half of emetic psychrotrophic B. cereus were able to produce cereulide in optimal conditions. At 4 °C none of the examined psychrotrophs produced cereulide. The results of this research highlight the high prevalence of B. cereus and the omnipresence of toxin gene harboring presumptive B. cereus that can grow at refrigerator temperatures, with a focus on cereulide producers.     

Detection and Isolation of Emetic Bacillus cereus Toxin Cereulide by Reversed Phase Chromatography

The emetic toxin cereulide is a 1.2 kDa dodecadepsipeptide produced by the food pathogen Bacillus cereus. As cereulide poses a serious health risk to humans, sensitive and specific detection, as well as toxin purification and quantification, methods are of utmost importance. Recently, a stable isotope dilution assay tandem mass spectrometry (SIDA–MS/MS)-based method has been described, and an method for the quantitation of cereulide in foods was established by the International Organization for Standardization (ISO). However, although this SIDA–MS/MS method is highly accurate, the sophisticated high-end MS equipment required for such measurements limits the method’s suitability for microbiological and molecular research. Thus, we aimed to develop a method for cereulide toxin detection and isolation using equipment commonly available in microbiological and biochemical research laboratories. Reproducible detection and relative quantification of cereulide was achieved, employing reversed phase chromatography (RPC). Chromatographic signals were cross validated by ultraperformance liquid chromatography–mass spectrometry (UPLC–MS/MS). The specificity of the RPC method was tested using a test panel of strains that included non-emetic representatives of the B. cereus group, emetic B. cereus strains, and cereulide-deficient isogenic mutants. In summary, the new method represents a robust, economical, and easily accessible research tool that complements existing diagnostics for the detection and quantification of cereulide.     

Characteristics of the Protein Complexes and Pores Formed by Bacillus cereus Hemolysin BL

Bacillus cereus Hemolysin BL is a tripartite toxin responsible for a diarrheal type of food poisoning. Open questions remain regarding its mode of action, including the extent to which complex formation prior to cell binding contributes to pore-forming activity, how these complexes are composed, and the properties of the pores formed in the target cell membrane. Distinct complexes of up to 600 kDa were found on native gels, whose structure and size were primarily defined by Hbl B. Hbl L1 and L2 were also identified in these complexes using Western blotting and an LC-MS approach. LC-MS also revealed that many other proteins secreted by B. cereus exist in complexes. Further, a decrease of toxic activity at temperatures ≥60 °C was shown, which was unexpectedly restored at higher temperatures. This could be attributed to a release of Hbl B monomers from tight complexation, resulting in enhanced cell binding. In contrast, Hbl L1 was rather susceptible to heat, while heat treatment of Hbl L2 seemed not to be crucial. Furthermore, Hbl-induced pores had a rather small single-channel conductance of around 200 pS and a probable channel diameter of at least 1 nm on planar lipid bilayers. These were highly instable and had a limited lifetime, and were also slightly cation-selective. Altogether, this study provides astonishing new insights into the complex mechanism of Hbl pore formation, as well as the properties of the pores.     

Acute Liver Failure after Ingestion of Fried Rice Balls: A Case Series of Bacillus cereus Food Poisonings

Bacillus cereus foodborne intoxications and toxicoinfections are on a rise. Usually, symptoms are self-limiting but occasionally hospitalization is necessary. Severe intoxications with the emetic Bacillus cereus toxin cereulide, which is notably resistant heat and acid during cooking, can cause acute liver failure and encephalopathy. We here present a case series of food poisonings in five immunocompetent adults after ingestion of fried rice balls, which were massively contaminated with Bacillus cereus. The patients developed a broad clinical spectrum, ranging from emesis and diarrhoea to life-threatening acute liver failure and acute tubular necrosis of the kidney in the index patient. In the left-over rice ball, we detected 8 × 10⁶ Bacillus cereus colony-forming units/g foodstuff, and cereulide in a concentration of 37 μg/g foodstuff, which is one of the highest cereulide toxin contaminations reported so far from foodborne outbreaks. This report emphasizes the potential biological hazard of contaminated rice meals that are not freshly prepared. It exemplifies the necessity of a multidisciplinary approach in cases of Bacillus cereus associated food poisonings to rapidly establish the diagnosis, to closely monitor critically ill patients, and to provide supportive measures for acute liver failure and—whenever necessary—urgent liver transplantation.     

Impact of Phytochemicals on Viability and Cereulide Toxin Synthesis in Bacillus cereus Revealed by a Novel High-Throughput Method,Coupling an AlamarBlue-Based Assay with UPLC-MS/MS

Due to its food-poisoning potential, Bacillus cereus has attracted the attention of the food industry. The cereulide-toxin-producing subgroup is of particular concern, as cereulide toxin is implicated in broadscale food-borne outbreaks and occasionally causes fatalities. The health risks associated with long-term cereulide exposure at low doses remain largely unexplored. Natural substances, such as plant-based secondary metabolites, are widely known for their effective antibacterial potential, which makes them promising as ingredients in food and also as a surrogate for antibiotics. In this work, we tested a range of structurally related phytochemicals, including benzene derivatives, monoterpenes, hydroxycinnamic acid derivatives and vitamins, for their inhibitory effects on the growth of B. cereus and the production of cereulide toxin. For this purpose, we developed a high-throughput, small-scale method which allowed us to analyze B. cereus survival and cereulide production simultaneously in one workflow by coupling an AlamarBlue-based viability assay with ultraperformance liquid chromatography–mass spectrometry (UPLC-MS/MS). This combinatory method allowed us to identify not only phytochemicals with high antibacterial potential, but also ones specifically eradicating cereulide biosynthesis already at very low concentrations, such as gingerol and curcumin.