Prevalence and expression of enterotoxins in Bacillus cereus and other Bacillus spp., a literature review (original) (raw)
Related papers
From soil to gut: Bacillus cereus and its food poisoning toxins
FEMS Microbiology Reviews, 2008
Bacillus cereus is widespread in nature and frequently isolated from soil and growing plants, but it is also well adapted for growth in the intestinal tract of insects and mammals. From these habitats it is easily spread to foods, where it may cause an emetic or a diarrhoeal type of food-associated illness that is becoming increasingly important in the industrialized world. The emetic disease is a food intoxication caused by cereulide, a small ring-formed dodecadepsipeptide. Similar to the virulence determinants that distinguish Bacillus thuringiensis and Bacillus anthracis from B. cereus, the genetic determinants of cereulide are plasmid-borne. The diarrhoeal syndrome of B. cereus is an infection caused by vegetative cells, ingested as viable cells or spores, thought to produce protein enterotoxins in the small intestine. Three pore-forming cytotoxins have been associated with diarrhoeal disease: haemolysin BL (Hbl), nonhaemolytic enterotoxin (Nhe) and cytotoxin K. Hbl and Nhe are homologous three-component toxins, which appear to be related to the monooligomeric toxin cytolysin A found in Escherichia coli. This review will focus on the toxins associated with foodborne diseases frequently caused by B. cereus. The disease characteristics are described, and recent findings regarding the associated toxins are discussed, as well as the present knowledge on virulence regulation.
The Food Poisoning Toxins of Bacillus cereus
Toxins
Bacillus cereus is a ubiquitous soil bacterium responsible for two types of food-associated gastrointestinal diseases. While the emetic type, a food intoxication, manifests in nausea and vomiting, food infections with enteropathogenic strains cause diarrhea and abdominal pain. Causative toxins are the cyclic dodecadepsipeptide cereulide, and the proteinaceous enterotoxins hemolysin BL (Hbl), nonhemolytic enterotoxin (Nhe) and cytotoxin K (CytK), respectively. This review covers the current knowledge on distribution and genetic organization of the toxin genes, as well as mechanisms of enterotoxin gene regulation and toxin secretion. In this context, the exceptionally high variability of toxin production between single strains is highlighted. In addition, the mode of action of the pore-forming enterotoxins and their effect on target cells is described in detail. The main focus of this review are the two tripartite enterotoxin complexes Hbl and Nhe, but the latest findings on cereulide...
Bacillus cereus is an opportunistic Food borne Pathogen that contaminates a wide variety of foods. There are mainly two types of illness caused by B. cereus in human beings namely diarrhoeal and emetic types. The emetic type is due to a single heat-stable toxin, and the diarrheal type to 3 or 4 heat-instable enterotoxins. In this research work, B. cereus spp were isolated from fermented rice noodle (Myanmar Traditional Food). For emetic toxin production, toxin of three isolated B. cereus were extracted by methanol extraction and subjected to LC-MS. Three isolated strains were genetically characterized by using gene specific primer for enterotoxin production. None of these strains showed emetic toxin production. But, all three strains tested had all the components of Haemolytic BL toxin (HBL), a haemolytic enterotoxin complex made of three proteins and Non Haemolytic Enterotoxin (NHE), a non-haemolytic enterotoxin complex made of three proteins and enterotoxin T genes. In addition, genes for the cytotoxin K were also found in two isolates, one isolate (E4) showed negative. From these results, the three isolates may be virulence because they have all HBL genes and all NHE genes. So, these strains seem to be enterotoxin producing strains.
Determination of the toxic potential ofBacillus cereusisolates by quantitative enterotoxin analyses
Fems Microbiology Letters, 2006
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-L 2 and NheB component ranged from 0.02 to 5.6 mg mL À1 and from 0.03 to 14.2 mg mL À1 , 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.
Toxin gene profiling of enterotoxic and emetic Bacillus cereus
FEMS Microbiology Letters, 2000
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.
Production, Secretion and Biological Activity of Bacillus cereus Enterotoxins
2010
Bacillus cereus behaves as an opportunistic pathogen frequently causing gastrointestinal diseases, and it is increasingly recognized to be responsible for severe local or systemic infections. Pathogenicity of B. cereus mainly relies on the secretion of a wide array of toxins and enzymes and also on the ability to undergo swarming differentiation in response to surface-sensing. In this report, the pathogenicity exerted by B. cereus toxins is described with particular attention to the regulatory mechanisms of production and secretion of HBL, Nhe and CytK enterotoxins.
Molecular Characterization and Enterotoxin Genes Typing of Local Strains of Bacillus Cereus
2009
Abstract: Two virulent strains of Bacillus cereus coded as BC13 and BC37 isolated from corn snacks collected from Egyptian market were identified using biochemical and staining methods. Further confirmation was done by determining their cellular protein pattern compared to a standard culture of B. cereus NRRL 569. The cellular protein profile revealed 97.55 to 99% similarity between NRRL 569 reference strain and local strains (BC13, BC37). Random amplification polymerase DNA analysis of the two tested isolates compared to standard culture using eleven arbitrary primers showed similarities ranging from 75.5% to 77.09% between the tested isolates. Separation of extracellular proteins of both tested isolates using SDS-PAGE revealed the presence of protein bands with molecular weights between 34 and 54 kDa in both tested isolates, suspected as enterotoxins. To ensure the presence of suspected enterotoxins, two pairs of primers newly designed and reported during year 2008 (FHblC and RHbl...
Bacillus cereus food poisoning in Indian perspective: A review
The Pharma Innovation Journal, 2021
Bacillus cereus is one of food-borne disease causing bacteria. Bacillus spores may be present on various types of raw and cooked foods and their ability to survive high cooking temperatures requires that cooked foods be served hot or cooled rapidly to prevent the growth of this bacteria. Bacillus cereus is well known as a cause of food poisoning and much more is now known about the toxins produced by various strains of this species. Bacillus cereus is widespread in nature and frequently isolated from soil and growing plants, but it is also well adapted for growth in the intestinal tract of insects and mammals. From these habitats it is easily spread to foods, where it may cause an emetic or a diarrhoeal type of foodassociated illness that is becoming increasingly important in the industrialized world. The emetic disease is a food intoxication caused by cereulide, a small ring-formed dodecadepsipeptide. The genetic determinants of cereulide are plasmid-borne. The diarrhoeal syndrome of B. cereus is an infection caused by vegetative cells, ingested as viable cells or spores, thought to produce protein enterotoxins in the small intestine. These are cytotoxins, have been associated with diarrhoeal disease are haemolysin BL, nonhaemolytic enterotoxin and cytotoxin K. This review will focus on the toxins associated with foodborne diseases frequently caused by B. cereus.
Bacillus cereus: an important foodborne pathogen
Journal of the Hellenic Veterinary Medical Society, 2018
Β. cereus is a spore-forming bacterium, frequently found in the environment. Most of the strains can grow at a temperature range of 10°-42° C. B. cereus grows under aerobic conditions, but anaerobic growth is, also, feasible. D 121 values of the spores of B. cereus strains are usually in the range of 0.03 to 2.35 min. The pathogen produces at least five different enterotoxins (HBL, Nhe, CytK, BceT and FM) and one emetic toxin. The enterotoxins HBL, Nhe and CytK are the etiological agents of the B. cereus diarrhoeal disease. The enterotoxins are heat sensitive and can be inactivated by heating at 56° C for 5 min. They are, also, sensitive to low pH and proteolytic activity of enzymes and, subsequently, are inactivated in the acid environment of the stomach. B. cereus emetic toxin has been kept stable even in a heat treatment at 121° C for 2 h in in vitro tests. The emetic toxin is highly resistant to low pH (as low as 2) and to proteolysis. Thus, the emetic toxin cannot be inactivated in the acidic environment of the stomach and the enzyme proteolytic activity in the intestinal tract. B. cereus causes either a diarrhoeal or an emetic type of foodborne disease. The diarrhoeal disease is caused by the B. cereus enterotoxins, which are formed in the intestinal tract after the spores' germination and the subsequent growth of the vegetative cells. The symptoms are watery diarrhoea, abdominal cramps and pain. The emetic disease is caused by the ingestion of the preformed toxins in the foods. The symptoms are nausea and vomiting, occasionally followed by abdominal pain or diarrhoea. Foodborne outbreaks caused by B. cereus have been associated with various foods. The emetic disease has often been associated with the consumption of rice, pasta and other starchy foods, while the diarrheal disease is often linked to the consumption of dairy products, vegetables and meat. The most common food sources for B. cereus infections in humans are milk and dairy products. Among the reported foodborne outbreak cases in North America, Europe and Japan attributed to B. cereus represent a percentage of 1% to 22%. Most B. cereus foodborne cases were associated with the consumption of cooked foods that were cooled slowly and stored under improper refrigeration conditions. Foodborne diseases caused byB. cereus constitute a major problem in restaurants and catering services. Application of control measures, such as Good Manufacturing Practices (GMP) and Hazard Analysis Critical Control Points system (HACCP), in food processing lines can prevent contamination of the foods with pathogens like B. cereus.
International Journal of Food Microbiology, 2008
The ability of various species of Bacillus from fermented seeds of Parkia biglobosa known as African locust bean (Soumbala) and fermented seeds of Hibiscus sabdariffa (Bikalga) was investigated. The study included screening of the isolates by haemolysis on blood agar, detection of toxins in broth and during the fermentation of African locust bean using the Bacillus cereus Enterotoxin Reverse Passive Latex Agglutination test kit (BCET-RPLA) and the Bacillus Diarrhoeal Enterotoxin Visual Immunoassay (BDEVIA). Detection of genes encoding cytotoxin K (CytK), haemolysin BL (Hbl A, Hbl C, Hbl D), non-hemolytic enterotoxin (NheA, NheB, NheC) and EM1 specific of emetic toxin producers was also investigated using PCR with single pair and multiplex primers. Of 41 isolates, 29 Bacillus belonging to the species of B. cereus, Bacillus subtilis, Bacillus licheniformis and Bacillus pumilus showed haemolysis on blood agar. Using RPLA, enterotoxin production was detected for three isolates of B. cereus in broth and all B. cereus (9) in fermented seeds. Using BDEVIA, enterotoxin production was detected in broth as well as in fermented seeds for all B. cereus isolates. None of the isolates belonging to the other Bacillus species was able to produce enterotoxins either by RPLA or BDEVIA. Nhe genes were detected in all B. cereus while Hbl and CytK genes were detected respectively in five and six B. cereus strains. A weak presence of Hbl (A, D) and CytK genes was detected in two isolates of B. subtilis and one of B. licheniformis but results were inconsistent, especially for Hbl genes. The emetic specific gene fragment EM1 was not detected in any of the isolates studied.