首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Abstract When grown for 15 h in rice culture, 13 out of 15 Bacillus cereus strains associated with emetic-syndrome food poisoning (87%) caused vacuoles to appear in HEp-2 cells, compared with 5 out of 11 B. cereus strains from other sources (45%). No other Bacillus species tested gave rise to this response under these conditions. Six out of eight rice samples involved in incidents of B. cereus emetic illness produced vacuoles in HEp-2 cells, whereas control rice samples and foods from vomiting episodes caused by other Bacillus spp. failed to do so. This vacuole response may have application as a simple in vitro assay for organisms and foods implicated in B. cereus emetic-syndrome food poisoning.  相似文献   

2.
Bacillus cereus causes two types of gastrointestinal diseases: emesis and diarrhea. The emetic type of the disease is attributed to the heat-stable depsipeptide cereulide and symptoms resemble Staphylococcus aureus intoxication, but there is no rapid method available to detect B. cereus strains causing this type of disease. In this study, a polymerase chain reaction (PCR) fragment of unknown function was identified, which was shown to be specific for emetic toxin producing strains of B. cereus. The sequence of this amplicon was determined and a PCR assay was developed on this basis. One hundred B. cereus isolates obtained from different food poisoning outbreaks and diverse food sources from various geographical locations and 29 strains from other species belonging to the B. cereus group were tested by this assay. In addition, 49 non-B. cereus group strains, with special emphasis on food pathogens, were used to show that the assay is specific for emetic toxin producing B. cereus strains. The presented PCR assay is the first molecular tool for the rapid detection of emetic toxin producing B. cereus strains.  相似文献   

3.
A method for high-resolution genomic fingerprinting of the enteric pathogens Campylobacter jejuni and Campylobacter coli, based on the determination of amplified fragment length polymorphism, is described. The potential of this method for molecular epidemiological studies of these species is evaluated with 50 type, reference, and well-characterised field strains. Amplified fragment length polymorphism fingerprints comprised over 60 bands detected in the size range 35-500 bp. Groups of outbreak strains, replicate subcultures, and 'genetically identical' strains from humans, poultry and cattle, proved indistinguishable by amplified fragment length polymorphism fingerprinting, but were differentiated from unrelated isolates. Previously unknown relationships between three hippurate-negative C. jejuni strains, and two C. coli var. hyoilei strains, were identified. These relationships corresponded to available epidemiological data. We conclude that this amplified fragment length polymorphism fingerprinting method may be a highly effective tool for molecular epidemiological studies of Campylobacter spp.  相似文献   

4.
Toxin production, biochemical properties and ribotypes of Bacillus cereus group (B. cereus, B. thuringiensis, B. mycoides) strains originating from industrial and environmental sources (n = 64), from food poisoning incidents (n = 22) and from reference sources (n = 7) were analysed. Forty ribotypes were found among the 93 strains. Eleven strains from food poisoning incidents produced emetic (mitochondrio) toxin, as determined by the boar spermatozoa toxicity test. These strains possessed closely similar ribotypes which were rare among strains of other origins. Sperm toxin producing (cereulide positive) strains did not hydrolyse starch and did not produce haemolysin BL, as determined by the reverse passive latex agglutination test. Sixteen different ribotypes were found among B. cereus strains from board machines (n = 16) and from packaging board (n = 16), indicating many different sources of B. cereus contamination in board mills. Strains originating from packaging board had predominantly different ribotypes from those of dairy and dairy product originating strains. Nine (53%) out of 17 strains from a single dairy process shared the same ribotype whereas strains from milk and milk products from different dairies had different ribotypes indicating that B. cereus group populations were dairy specific. Twenty-two percent of strains isolated from the paperboard industry on non-selective medium were lecithinase negative, including enterotoxin producing strains. This stresses the importance of other detection methods not based on a positive lecithinase reaction.  相似文献   

5.
Seventy-four strains of Bacillus thuringiensis 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. Microbiological Societies.  相似文献   

6.
Pathogenic Bacillus cereus can be routinely isolated and identified in the laboratory from foods and other sources. Typing of B. cereus strains implicated in food poisoning outbreaks is helpful for confirmation of the origin of the outbreak and for epidemiological studies. Data concerning vegetative growth and spores are given. Different types of toxin are produced by B. cereus in the course of its growth: a so-called diarrheal enterotoxin and an emetic heat-stable toxin; their biochemical characteristics and the systems used for their detection are reviewed. Different types of hemolysins and phospholipases C are also produced and may play a role in pathogenicity. Nongastrointestinal infections were also traced to this species.  相似文献   

7.
Very different toxins are responsible for the two types of gastrointestinal diseases caused by Bacillus cereus: the diarrhoeal syndrome is linked to nonhemolytic enterotoxin NHE, hemolytic enterotoxin HBL, and cytotoxin K, whereas emesis is caused by the action of the depsipeptide toxin cereulide. The recently identified cereulide synthetase genes permitted development of a molecular assay that targets all toxins known to be involved in food poisoning in a single reaction, using only four different sets of primers. The enterotoxin genes of 49 strains, belonging to different phylogenetic branches of the B. cereus group, were partially sequenced to encompass the molecular diversity of these genes. The sequence alignments illustrated the high molecular polymorphism of B. cereus enterotoxin genes, which is necessary to consider when establishing PCR systems. Primers directed towards the enterotoxin complex genes were located in different CDSs of the corresponding operons to target two toxin genes with one single set of primers. The specificity of the assay was assessed using a panel of B. cereus strains with known toxin profiles and was successfully applied to characterize strains from food and clinical diagnostic labs as well as for the toxin gene profiling of B. cereus isolated from silo tank populations.  相似文献   

8.
目的:利用扩增片段长度多态性(AFLP)分析建立鉴别炭疽芽孢杆菌和蜡样芽孢杆菌的分子生物学方法。方法:3株炭疽芽孢杆菌和3株蜡样芽孢杆菌基因组经限制性内切酶EcoRⅠ和MseⅠ酶切后与对应接头连接,通过预扩增和选择性扩增获得特异性DNA片段,将片段进行毛细管电泳,并利用GeneScan和BioNumerics软件对电泳数据进行分析。结果:选择性扩增最佳引物组合为EcoRⅠ-G/MseⅠ-A,其扩增片段在100~500 bp范围内的有效数量为40~50条;比较炭疽芽孢杆菌和蜡样芽孢杆菌的AFLP特征峰值图和DNA指纹图谱,确定了5个有明显差异的片段区。结论:利用AFLP分析可对芽孢杆菌属中相近的炭疽芽孢杆菌和蜡样芽孢杆菌进行鉴别,该方法可作为炭疽芽孢杆菌传统鉴定方法的补充。  相似文献   

9.
The epidemiology of Bacillus cereus strains responsible for food poisoning is scantly known, mostly because the genotypic and toxigenic properties of the B. cereus strains isolated during food-poisoning outbreaks have been never catalogued. The occurrence of two simultaneous food-poisoning outbreaks gave us the opportunity to wonder whether (i) the identity of individual strains isolated from clinical, environmental, and food samples could be established by random amplified polymorphic DNA (RAPD)-PCR and multiplex RAPD-PCR, and (ii) the toxigenic potential of the isolates could be determined by testing their ability to secrete hemolysin BL, phosphatidylcholine-specific phospholipase C, and cereulide, as well as by determining the presence of the genes encoding enterotoxins NHE, T, and FM/S, cytotoxin K, sphingomyelinase, and phosphatidylinositol-specific phospholipase C. This is the first report demonstrating that the combination of several phenotypic and genotypic traits provides a powerful tool for tracing the source of infection of toxigenic B. cereus strains relevant for epidemiological survey.  相似文献   

10.
An egg yolk-polymyxin medium (KG) for rapid enumeration of Bacillus cereus is described. The test is presumptive in that differentiation of B. cereus (and closely related organisms) from other species is based on the formation of turbidity in the agar surrounding the colonies of the cereus group organisms. The medium is formulated to encourage sporulation and release of free spores for serological confirmatory tests within the 24-hr incubation period. The production of turbidity in egg yolk and free-spore production by 25 strains of B. cereus on KG agar were measured. The recovery of food poisoning strains of B. cereus inoculated into nonsterile food slurries was assessed. A comparison of KG agar and mannitol-egg yolk-polymyxin-agar indicated that the two media were comparable in their abilities to recover low levels of B. cereus from naturally contaminated foods. Since KG agar enhances spore formation by B. cereus, thus permitting early serological testing, its use in screening food products is advocated.  相似文献   

11.
Haemolysin BL (HBL) and non-haemolytic enterotoxin (Nhe), each consisting of three components, represent the major enterotoxins produced by Bacillus cereus. To evaluate the expression of these toxins, a set of 100 B. cereus strains was examined. Molecular biological characterization showed that 42% of the strains harboured the genes for HBL and 99% for Nhe. The production of all Nhe and HBL components were analyzed using specific antibodies and, in culture supernatants, detectable levels of HBL and Nhe were found for 100% of hbl-positive and 96% of nhe-positive strains. The concentrations of the HBL-L(2) and NheB component ranged from 0.02 to 5.6 microg mL(-1) and from 0.03 to 14.2 microg mL(-1), respectively. Comparison of the amount of NheB produced by food poisoning and food/environmental strains revealed that the median value for all food poisoning strains was significantly higher than for the food/environmental isolates. The data presented in this study provide evidence that specific and quantitative determination of the enterotoxins is necessary to evaluate the toxic potential of B. cereus. In particular, the level of Nhe seems to explain most of the cytotoxic activity of B. cereus isolates and may indicate a highly diarrheic potential.  相似文献   

12.
We examined 154 Norwegian B. cereus and B. thuringiensis soil isolates (collected from five different locations), 8 B. cereus and 2 B. thuringiensis reference strains, and 2 Bacillus anthracis strains by using fluorescent amplified fragment length polymorphism (AFLP). We employed a novel fragment identification approach based on a hierarchical agglomerative clustering routine that identifies fragments in an automated fashion. No method is free of error, and we identified the major sources so that experiments can be designed to minimize its effect. Phylogenetic analysis of the fluorescent AFLP results reveals five genetic groups in these group 1 bacilli. The ATCC reference strains were restricted to two of the genetic groups, clearly not representative of the diversity in these bacteria. Both B. anthracis strains analyzed were closely related and affiliated with a B. cereus milk isolate (ATCC 4342) and a B. cereus human pathogenic strain (periodontitis). Across the entire study, pathogenic strains, including B. anthracis, were more closely related to one another than to the environmental isolates. Eight strains representing the five distinct phylogenetic clusters were further analyzed by comparison of their 16S rRNA gene sequences to confirm the phylogenetic status of these groups. This analysis was consistent with the AFLP analysis, although of much lower resolution. The innovation of automated genotype analysis by using a replicated and statistical approach to fragment identification will allow very large sample analyses in the future.  相似文献   

13.
We analyzed the genetic relationships and molecular characteristics of 34 Bacillus anthracis isolates from soil and clinical samples in various regions of Korea and 17 related Bacillus species, using the amplified fragment length polymorphism (AFLP) and multilocus variable-number tandem repeat (MLVA) approaches. Triplicate AFLP profiles of these strains showed high reproducibility and identified 376 polymorphisms. AFLP phylogenetic analysis of B. anthracis isolates showed a high level of similarity, 0.93, and this monomorphic fragment profile proved to be useful to differentiate B. anthracis strains from other Bacillus species. The B. cereus group was separated from other Bacillus species at a level of similarity of 0.68. Among them, some B. cereus strains showed genetic interspersion with B. thuringiensis strains. The evolutionary pattern of nucleotide differences among B. anthracis strains with the eight MLVA markers showed nine MLVA types. Three MLVA types, M1 to M3, were pathogenic B. anthracis isolates and were assigned as new genotypes belonging to the A4 and B3 clusters, compared with 89 genotypes deduced from previous data. This indicates that differences in cluster prevalence and distribution may be influenced more by MLVA markers on two plasmids loci and human activity. Consequently, we suggest that the novel MLVA type may represent significant evidence for historic adaptation to environmental conditions of the Asian continent, particularly Korea. Therefore, MLVA techniques may be available for molecular monitoring on anthrax-release-related bioterrorism and further study is required for the continuous epidemiological study of variable anthrax collections.  相似文献   

14.
DNA from over 300 Bacillus thuringiensis, Bacillus cereus, and Bacillus anthracis isolates was analyzed by fluorescent amplified fragment length polymorphism (AFLP). B. thuringiensis and B. cereus isolates were from diverse sources and locations, including soil, clinical isolates and food products causing diarrheal and emetic outbreaks, and type strains from the American Type Culture Collection, and over 200 B. thuringiensis isolates representing 36 serovars or subspecies were from the U.S. Department of Agriculture collection. Twenty-four diverse B. anthracis isolates were also included. Phylogenetic analysis of AFLP data revealed extensive diversity within B. thuringiensis and B. cereus compared to the monomorphic nature of B. anthracis. All of the B. anthracis strains were more closely related to each other than to any other Bacillus isolate, while B. cereus and B. thuringiensis strains populated the entire tree. Ten distinct branches were defined, with many branches containing both B. cereus and B. thuringiensis isolates. A single branch contained all the B. anthracis isolates plus an unusual B. thuringiensis isolate that is pathogenic in mice. In contrast, B. thuringiensis subsp. kurstaki (ATCC 33679) and other isolates used to prepare insecticides mapped distal to the B. anthracis isolates. The interspersion of B. cereus and B. thuringiensis isolates within the phylogenetic tree suggests that phenotypic traits used to distinguish between these two species do not reflect the genomic content of the different isolates and that horizontal gene transfer plays an important role in establishing the phenotype of each of these microbes. B. thuringiensis isolates of a particular subspecies tended to cluster together.  相似文献   

15.
Simple double repetitive element polymerase chain reaction (MaDRE-PCR) and Pvu II-IS1245 restriction fragment length polymorphism (RFLP) typing methods were used to type 41 Mycobacterium avium isolates obtained from 14 AIDS inpatients and 10 environment and animals specimens identified among 53 mycobacteria isolated from 237 food, chicken, and pig. All environmental and animals strains showed orphan patterns by both methods. By MaDRE-PCR four patients, with multiple isolates, showed different patterns, suggesting polyclonal infection that was confirmed by RFLP in two of them. This first evaluation of MaDRE-PCR on Brazilian M. avium strains demonstrated that the method seems to be useful as simple and less expensive typing method for screening genetic diversity in M. avium strains on selected epidemiological studies, although with limitation on analysis identical patterns except for one band.  相似文献   

16.
Certain properties of 22 Bacillus cereus strains isolated from different foods and food poisoning episodes were investigated in order to evaluate possible différences between strains isolated from diarrhoeal and vomiting type food poisoning outbreaks. None of the strains isolated from vomiting type episodes produced acid from salicin and mannose, whereas 80 and 40 % of the strains from diarrhoeal type outbreaks were positive, respectively. No association between the antibiotic sensitivity pattern or the fatty acid composition and the source of a strain could be found, although some strains differed from the general pattern of B. cereus in some instances. No significant differences in the production of the skin factor between strains isolated from the two types of outbreaks were found either. The findings of this study support the observation that the food environment itself essentially affects the enterotoxin formation of B. cereus.  相似文献   

17.
Fluorescent amplified fragment length polymorphism (FAFLP) analysis was applied to genetically fingerprint 'working culture control strains' used by accredited food microbiology laboratories. A working culture control strain is defined as a subculture from a strain initially obtained from an authenticated source [such as the National Collection of Type Cultures (NCTC)] that is maintained for use with routine testing within the laboratory. Working culture control strains from eight food examination laboratories, representing four bacterial species, were analysed by FAFLP; these were Salmonella Nottingham, Staphylococcus aureus, Listeria monocytogenes and Bacillus cereus. The resultant FAFLP profiles of the eight working culture control strains for each of these species were compared against the appropriate freeze-dried ampoules obtained directly from NCTC. FAFLP results demonstrated that within 50% of working cultures analysed, several laboratories were routinely using working cultures that were genetically different from the original reference NCTC strains. This study highlights the need for laboratories to review the protocols used to process and maintain control strains and working cultures, with a potential view to utilize single-use quality control materials.  相似文献   

18.
Bacillus cereus causes distinct exotoxin-mediated diarrheal and emetic food poisoning syndromes and a variety of nongastrointestinal infections. Evidence is accumulating that hemolysin BL is a major B. cereus virulence factor. We describe two methods for detection of hemolysin BL in crude samples and on primary culture media. In the first method, the highly unusual discontinuous hemolysis pattern that is characteristic of pure hemolysin BL was produced in sheep and calf blood agar around wells filled with crude culture supernatant from hemolysin BL-producing strains. In the second method, the pattern was formed surrounding colonies of hemolysin BL-producing strains grown on media consisting of nutrient agar, 0.15 M NaCl, 2% calf serum, and sheep or calf blood. Hemolysin BL production was detected with these methods in 41 of 62 (66%) previously identified B. cereus isolates and in 46 of 136 (34%) presumptive B. cereus isolates from soil. All nine isolates tested that were associated with diarrhea or nongastrointestinal illness were positive for hemolysin BL. The methods presented here are specific, simple, inexpensive, and applicable to the screening of large numbers of samples or isolates.  相似文献   

19.
In a survey of 39 dried food samples which represented 12 different pulses and cereals. 22 (56%) were found to be contaminated with Bacillus cereus. The numbers varied between 1 times 102 and 6 times 104 organisms/g. During normal cooking procedures and on storage at room temperature, the B. cereus resident on red lentils and kidney beans increased to a level at which enterotoxin production could become significant. Some physiological characteristics including deoxyribonuc-lease (DNase) and ribonuclease (RNase) secretion and salicin fermentation did not correlate with the ability or otherwise of a strain to cause food poisoning. Nevertheless, serotype 8 strains were prevalent on these foods and these have been implicated in both the diarrhoeal and vomiting-type food poisoning syndromes.  相似文献   

20.
Lee JH  Shin H  Son B  Ryu S 《Journal of virology》2012,86(1):637-638
Bacillus cereus is generally found in soil habitats, and it contaminates a wide variety of foods, causing food poisoning with symptoms such as vomiting and diarrhea. To develop a novel biocontrol agent to inhibit this pathogen, bacteriophage BCP78 belonging to the Siphoviridae family was isolated from a fermented food sample. Here we announce the complete genome sequence of BCP78, which may be useful for understanding its inhibition mechanism against B. cereus, and describe major findings from the genome annotation.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号