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Cereus Strains (cereus + strain)
Kinds of Cereus Strains Selected AbstractsImpact of different pasteurization temperatures on the survival of microbial contaminants isolated from pasteurized milkINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 2 2005PHOLISA DUMALISILE The thermal inactivation of selected microbes was studied using the low temperature long time (LTLT), high temperature short time (HTST) and ,pot' pasteurization methods. Survivors were enumerated after heating for up to 40 min for the LTLT and HTST pasteurization methods and after heating for up to 30 min for the ,pot' pasteurization method. With the exception of the Bacillus cereus strain, the selected microbes did not survive the LTLT and HTST pasteurization methods. The results from the ,pot' pasteurizer showed that B. cereus, Chryseobacterium meningosepticum, Pseudomonas putida, Acinetobacter baumannii and Escherichia coli strains survived the pasteurization conditions applied, showing that the ,pot' pasteurizer does not pasteurize effectively. [source] Effects of porcine bile on survival of Bacillus cereus vegetative cells and Haemolysin BL enterotoxin production in reconstituted human small intestine mediaJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2007T. Clavel Abstract Aims: To determine the effects of porcine bile (PB) on Bacillus cereus vegetative cells and Haemolysin BL (HBL) enterotoxin production in reconstituted small intestine media (IM). Methods and Results: The effects of PB on the growth of B. cereus vegetative cells in reconstituted IM at PB concentrations ranging between 0 and 3·0 g l,1 were examined. Four gastric media (GM) named GM-J broth (JB), GM-chicken, GM-milk and GM-pea were prepared by mixing equal volumes of a gastric electrolyte solution containing pepsin with JB, chicken, semi-skimmed milk and pea soup, respectively. Bacillus cereus was inoculated at approx. 2 × 104 CFU ml,1 into each GM at pH 5·0 for 30 min at 37°C, then mixed to the same volume of double-strength JB (IM) and PB to give concentrations of between 0 and 3·0 g of PB per litre at pH 6·5 and incubated at 37°C. The diarrhoeal B. cereus strain F4430/73 grew in IM-JB, IM-chicken and IM-milk at PB concentrations of up to 0·6, 1·5 and 1·2 g l,1, respectively. Growth was observed in IM-pea at all concentrations tested. The highest PB concentrations allowing a 3 log B. cereus increase in IM-JB, IM-chicken, IM-milk and IM-pea after a 7,10 h incubation period were 0·3, 0·9, 0·9 and 3·0 g l,1, respectively. The effect of PB on B. cereus cells was strongest in IM-JB, followed by IM-chicken, IM-milk and IM-pea. Haemolysin BL enterotoxin was detectable in IM-chicken, IM-whole milk, IM-semi-skimmed milk and IM-pea up to PB concentrations of only 0·6, 0·6, 0·3 and 0·9 g l,1, respectively. The diarrhoeal B. cereus strain F4433/73 behaved similarly to B. cereus strain F4430/73, whereas the food strain TZ415 was markedly more susceptible to bile. Conclusions: The tolerance of B. cereus cells to PB strongly depends on the type of food contained in the IM. Bile tolerance is also subject to strain variation. Significance and Impact of the Study: The probability that B. cereus cells will grow in the small intestine, produce toxins and cause diarrhoea is likely to depend on the food they are ingested with, on the bile tolerance of the B. cereus strain, and on bile concentration. [source] Distribution of S-layers on the surface of Bacillus cereus strains: phylogenetic origin and ecological pressureENVIRONMENTAL MICROBIOLOGY, Issue 8 2001Tâm Mignot Bacillus anthracis, Bacillus cereus and Bacillus thuringiensis have been described as members of the Bacillus cereus group but are, in fact, one species. B. anthracis is a mammal pathogen, B. thuringiensis an entomopathogen and B. cereus a ubiquitous soil bacterium and an occasional human pathogen. In two clinical isolates of B. cereus, in some B. thuringiensis strains and in B. anthracis, an S-layer has been described. We investigated how the S-layer is distributed in B. cereus, and whether phylogeny or ecology could explain its presence on the surface of some but not all strains. We first developed a simple biochemical assay to test for the presence of the S-layer. We then used the assay with 51 strains of known genetic relationship: 26 genetically diverse B. cereus and 25 non- B. anthracis of the B. anthracis cluster. When present, the genetic organization of the S-layer locus was analysed further. It was identical in B. cereus and B. anthracis. Nineteen strains harboured an S-layer, 16 of which belonged to the B. anthracis cluster. All 19 were B. cereus clinical isolates or B. thuringiensis, except for one soil and one dairy strain. These findings suggest a common phylogenetic origin for the S-layer at the surface of B. cereus strains and, presumably, ecological pressure on its maintenance. [source] An assay system for the detection of phospholipase C activityEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 10 2003Markus Durban Abstract Phospholipase C (PLC, EC 3.1.4.3) enzymes specifically hydrolyze the C-O-P-bond in phospholipids, yielding sn -1, 2(2, 3)-diglycerides and a phosphate residue bearing the corresponding head group. Biochemical characterization of PLC requires methods for determination of activity. During characterization and purification, proteins are separated by polyacrylamide gel electrophoresis (PAGE). For direct identification and visualization of PLC, a new assay for activity staining in native and renatured SDS-PAGE is described. Incubation of a gel containing an active PLC in the presence of ,-naphthylphosphorylcholine leads to ,-naphthol formation. This reacts with the diazonium salt Fast Red, forming a red dye which allows clear determination of PLC purity, molecular weight and substrate specificity. The assay was verified using commercially available PC-PLC and new PC-PLC-producing Bacillus cereus strains. The substrate ,-NPC was prepared by chemical synthesis at an overall yield of 12%. [source] Determination of the toxic potential of Bacillus cereus isolates by quantitative enterotoxin analysesFEMS MICROBIOLOGY LETTERS, Issue 2 2006Maximilian Moravek Abstract Haemolysin BL (HBL) and nonhaemolytic 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,L2 and NheB component ranged from 0.02 to 5.6 ,g mL,1 and from 0.03 to 14.2 ,g 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. [source] Prevalence and characterisation of Bacillus cereus in vacuum packed potato pureeINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 8 2006Andreja Rajkovic Summary Refrigerated processed foods of extended durability (REPFED) potato puree was analysed for Bacillus cereus contamination along the production line and during the product shelf-life. Isolated B. cereus strains were tested for their psychrotrophic character and the ability to produce enterotoxins. Bacillus cereus contamination during four subsequent productions was in the range of 2.3,4.0 log cfu g,1. Productions five and six were significantly less contaminated with B. cereus (,1 log cfu g ,1). All B. cereus isolates from the first four productions were able to grow at 7 ° and 10 °C, whereas the majority of the isolates from productions five and six did not. No B. cereus isolates grew at 4 °C. randomly amplified polymorphic DNA (RAPD) fingerprinting showed that the most of B. cereus contamination originated from one source. In total, 30.4% of isolates expressed enterotoxic character. The present study points out the necessity to prevent an ,in house' colonisation and contamination during food processing in order to accomplish the safety of REPFED throughout the shelf-life. It also indicates the most critical steps in the production line of ready-to-eat potato puree and impact of failures regarding the food safety. The data provided can be used for risk assessment studies regarding B. cereus in REPFED. [source] Bacillus cereus is common in the environment but emetic toxin producing isolates are rareJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2006M. Altayar Abstract Aims:, To determine the incidence of emetic toxin producing Bacillus cereus in soil, animal faeces and selected vegetable produce to compare the results with the previously reported high incidence in rice paddy fields. To examine whether the emetic toxin has antibiotic activity. Methods and Results:, The incidence of emetic toxin producing B. cereus was evaluated by plating on selective agar 271 samples of soils, animal faeces, raw and processed vegetables. Overall, 45·8% of samples were positive for B. cereus. One hundred and seventy-seven B. cereus isolates were recovered at 30°C with the grand mean spore count being 2·6 ± 1·7 log10 CFU g,1 and 148 B. cereus isolates were recovered at 7°C with the grand mean spore count being 2·2 ± 1·2 log10 CFU g,1 of the177 B. cereus isolated at 30°C, only 3 were positive for emetic toxin production at a titre of 1/64, 1/32, 1/16, respectively. Also, 1 of 148 B. cereus isolated at 7°C was positive for emetic toxin production to a titre of 1/128. All positive isolates came from washed or unwashed potato skins, one was psychrotrophic as determined by PCR and growth at 7°C on subculture. The emetic toxin was not shown to have any antibiotic effects in growth inhibition studies. Conclusions:, While B. cereus was a common isolate, the incidence of the emetic strain was rare. This is in contrast to previous findings of the high incidence in rice paddy fields and the processing environment, which may suggest rice is a selective area for growth of the emetic strain of B. cereus. Significance and Impact of Study:, The finding that a psychrotrophic isolate of B. cereus can produce emetic toxin is the first ever such observation and suggests the possibility that psychrotrophic isolates could grow in refrigerated fresh foods and cause emesis. The incidence of emetic B. cereus strains in rice paddy fields now requires further study for comparison with the low incidence found in other soils. The emetic toxin failed to inhibit the growth of other bacterial, fungal and yeast species. Whether the toxin (which is similar in structure to the antibiotic valinomycin) plays a competitive role in the environment therefore remains unclear. [source] Characterization of spore appendages from Bacillus cereus strainsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2001T. Stalheim Aims:,Further characterization and comparison of spore appendages from Bacillus cereus strains. Methods and Results:,Appendages were isolated from 10 B. cereus strains from the food industry and food-borne outbreaks. The appendage proteins were dissolved in sample buffer containing 2% SDS and 5% mercaptoethanol at 100°C, and subjected to SDS-PAGE. None of the appendages showed identical protein patterns. Western blots, using antibodies raised against a 3·5 kDa appendage protein, showed that the majority of the appendage proteins reacted with the antibody. Removal of the appendages by sonic treatment of the spores did not alter their heat resistance. The appendages were digested by proteinase K, pepsin, and the enzymes in the detergent Paradigm 10, but not by trypsin or chymotrypsin. Spore adhesion to stainless steel was scarcely affected by removal of the appendages. Digestion of adhered intact spores (with appendages) with Paradigm 10 showed a high degree of variation. Conclusions:,Spore appendages from B. cereus are complex proteinaceous structures that differ among strains. Significance and Impact of the Study:,Information about spore appendages and their involvement in spore adhesion is crucial for improving cleaning methods used for control of bacterial spores in the food industry. [source] CYTOTOXICITY ASSESSMENT OF BACILLUS STRAINS ISOLATED FROM STREET-VENDED FOODS IN JOHANNESBURG, SOUTH AFRICAJOURNAL OF FOOD SAFETY, Issue 2 2002F.M. MOSUPYE ABSTRACT Twenty-one isolates each of Bacillus (B.) cereus, B. licheniformis and B. subtilis from street foods, collected in central Johannesburg, were randomly selected to test for cytotoxicity against McCoy 5A Mouse cells using a 3-(4,5-dimethylthizol-2-yl)-2,5-diphenyltetrazolium bromide assay, and observation by confocal scanning laser microscopy (CSLM) and scanning electron microscopy (SEM). Forty-eight percent of B. cereus, 33% of B. licheniformis and 19% of B. subtilis strains produced cytotoxic compounds. For B. cereus strains, all supernatants exhibiting cytotoxic effects were inactivated by heat treatment at 121C for 15 min. By contrast, 24% of B. licheniformis and 10% of B. subtilis supernatants exhibited cytotoxic effects following heat treatment. CSLM and SEM showed that McCoy cells treated with cytotoxic supernatants exhibited leakage and necrosis. Presence of B. cereus, B. licheniformis and B. subtilis in street foods in high numbers may pose potetnial safety risks due to production of cytotoxic compounds. [source] | |||||||||||||