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PubMed1993

A 48 kilodalton enterotoxin-related protein from Clostridium perfringens vegetative and sporulating cells.

Sporulating and vegetative cell extracts of enterotoxin-positive and enterotoxin-negative strains of Clostridium perfringens were examined by Western blotting using enterotoxin antiserum. A 48-kDa enterotoxin-related protein was found in vegetative and sporulating cell extracts of both toxin types. The results question previous reports about the ability of vegetative cells and presumptive enterotoxin-negative strains of this organism to produce enterotoxin, a protein with a molecular weight of 34 kDa.

Blotting, Western↗

PubMed1987

Vibrio cholerae metalloproteinase degrades intestinal mucin and facilitates enterotoxin-induced secretion from rat intestine.

Mucin secretion in situ from rat intestinal loops was promoted more effectively by dialysed crude cholera filtrate than by an equivalent amount of purified enterotoxin. The filtrate could be rendered inactive by incubation with mixed gangliosides or passage through a GM1-affinity column, which indicated that the secretory action of the filtrate depended upon its enterotoxin component. In an effort to explain the greater potency of the filtrate, we established the presence of a metalloproteinase in the filtrate and demonstrated that this enzyme was capable of degrading purified rat intestinal mucin. Sufficient degradation occurred to cause a substantial decrease in viscosity (57% in 120 min). Biochemical analysis of the mucin before and after exposure to filtrate revealed a rise in the combined percentage of serine, threonine and proline (53-58%), suggesting that poorly glycosylated areas (which are less abundant in these amino acids) were being partly removed from the mucin. The carbohydrate composition was essentially unaltered. Inhibition of the filtrate metalloproteinase by Zincov and alpha 2-macroglobulin significantly (P less than 0.005) reduced the ability of cholera filtrate to degrade mucin or to stimulate mucin secretion from rat intestinal slices in vitro. Purified cholera enterotoxin added to enterotoxin-depleted filtrate was a more potent secretagogue (secretory stimulant) in intestinal loops than an equivalent amount of enterotoxin alone. We therefore propose that mucin secretion induced by cholera filtrate is caused by cholera enterotoxin, but that degradation of the protective epithelial mucus layer by a constituent metalloproteinase may assist the toxin by allowing increased access to mucosal GM1 receptor sites.

Amino Acids↗

PubMed1992

Stimulation of neutrophil leukocyte chemotaxis by a cloned cytolytic enterotoxin of Aeromonas hydrophila.

A cytolytic enterotoxin produced by Aeromonas hydrophila, isolate SSU, has been cloned in our laboratory. This enterotoxin lysed rabbit red blood cells, destroyed Chinese hamster ovary cells, caused fluid secretion in rat ligated ileal loops, inhibited the phagocytic function of mouse phagocytes, and was lethal to mice when injected intravenously. In this study, the effect of this cytolytic enterotoxin on the chemotaxis of human leukocytes (cell line RPMI 1788) was examined. This toxin, at concentrations from 92.5 to 370 ng/ml, significantly stimulated the chemotactic activity of human leukocytes in a dose-dependent fashion. The stimulation of leukocyte chemotaxis elicited by cytolytic enterotoxin was abolished when the toxin was neutralized, heated, or exposed to low pH values. This stimulatory effect also was inhibited by various concentrations of pertussis toxin. These results demonstrated that cytolytic enterotoxin may stimulate increased chemotaxis of human leukocytes, and suggest that human leukocytes may possess cytolytic enterotoxin receptors which may be coupled to pertussis toxin-sensitive G-protein.

Aeromonas hydrophila↗

PubMed1988

Production of a heat stable enterotoxin by Plesiomonas shigelloides.

Eight strains of Plesiomonas shigelloides were assayed for enterotoxin production in the rabbit ileal loop assay. Seven strains required serial in vivo passage in the rabbit's intestine before enterotoxin activity was detected in the cells' filtrate. Enterotoxin production was readily lost with subculture of these toxinogenic cells. Heat treatment of the cells' filtrate from three strains that had never been passed in vivo led to detectable enterotoxin activity in three of six separate assays. Using LT, CT, STIa, STIb and STII as probes, no homology to the whole cell DNA of the eight strains was detected on Southern hybridization under low stringency conditions. The enterotoxin of P. shigelloides appears to be novel since production is induced by in vivo passage, activity is seen with heat treatment of cells' filtrate and there is no DNA homology to the cloned enterotoxin genes of Escherichia coli and Vibrio cholerae.

Animals↗

PubMedDate not supplied

Erythrocyte receptors for cholera and heat-labile enterotoxins of Escherichia coli.

Many serological reactions using red blood cells (RBC) such as radial immune haemolysis (RIH) and indirect haemagglutination (IH) tests have often been used for the detection of cholera toxin (CT) and heat-labile (LT) enterotoxin produced by porcine and human Escherichia coli strains. In these tests, the enterotoxins bind to sheep, bovine and guinea-pig RBC without any ligand. We studied several factors which might interfere with such binding, as well as the nature of the receptors involved. Treatment of erythrocytes with different enzymes revealed that proteolytic enzymes had no effect on the adsorption of enterotoxins to RBC. Conversely, treatment with neuraminidase increased the adsorption. Experiments carried out with delipidized RBC revealed that none of the enterotoxins under study bound to the cells thus treated. Pre-incubation of ganglioside fractions with the enterotoxins blocked RIH and IH reactions and the biological effect of them on Vero cells. Assaying RBC ganglioside fractions by thin-layer chromatography revealed the presence of GM1. Our results suggest that the receptors for GT and LT enterotoxins in sheep, bovine and guinea pig RBC are gangliosides: mainly GM1.

Absorption↗

PubMed1993

Inhibition of 5-hydroxytryptamine- and enterotoxin-induced fluid secretion by 5-HT receptor antagonists in the rat jejunum.

The effects of cholera toxin and heat stable Escherichia coli (E. coli) enterotoxin on intestinal fluid secretion are commonly considered to be mediated by cyclic nucleotides. It was demonstrated recently, by using the 5-hydroxytryptamine (5-HT)2 receptor antagonist ketanserin and the 5-HT3 receptor antagonist tropisetron, that 5-HT acts as an important mediator in cholera toxin- and heat stable E. coli enterotoxin-induced fluid secretion. In the present investigation ketanserin and tropisetron were compared with the newer 5-HT3 receptor antagonists ondansetron and granisetron versus 5-HT-, cholera toxin- and heat stable E. coli enterotoxin-induced fluid secretion in the rat jejunum in vivo. Both ondansetron and granisetron dose-dependently inhibited 5-HT- and enterotoxin-induced fluid secretion. Ketanserin blocked 5-HT-induced fluid secretion, but only diminished enterotoxin-induced effects even at higher doses. Tropisetron inhibited 5-HT- and cholera toxin-induced effects at high dose but only diminished heat stable E. coli enterotoxin-induced effects. We conclude that 5-HT3 receptors, located on enterochromaffin cells and nervous structures, are more important in mediating fluid secretion than 5-HT2 receptors, located on the epithelial cells.

Animals↗

PubMed1998

Neutrophil migration induced by staphylococcal enterotoxin type A in mice: a pharmacological analysis.

Staphylococcal enterotoxin type A induced marked neutrophil migration into the mouse peritoneal cavity and was dependent on the number of resident macrophages. This migratory response was dose- (16-64 microg of staphylococcal enterotoxin type A/cavity) and time-dependent, peaking at 12 h and disappearing after 72 h. Dexamethasone (0.5 mg/kg) inhibited the neutrophil migration induced by staphylococcal enterotoxin type A (32 microg; 42% inhibition). A similar response was observed with the platelet-activating factor-acether receptor antagonist, BN 52021 (ginkgolide B, 3-(1,1-dimethylethyl)-hexahydro-1,4-7b-trihydroxy-8-methyl-9H-1,7alph a (epoxymethano-1H,6alphaH-cyclopenta (c) furo (2,3-b) furo (3', 2': 3,4) cyclopenta (1,2-d) furan-5, 9, 12 (4H)-trione); 10 mg/kg; 57% inhibition), the histamine H2 receptor antagonist, cimetidine (2 mg/kg; 31% inhibition), the lipoxygenase inhibitor, BWA4C (N-(3-phenoxycinnamyl) acetohydroxamic acid); 10 mg/kg; 73% inhibition), and capsaicin (trans-8-methyl-N-vanillyl-6-nonamide), a sensory C-fiber neuropeptide depletor. In contrast, indomethacin (5 mg/kg) had no effect on staphylococcal enterotoxin type A-induced chemotaxis. We conclude that the peritonitis induced by staphylococcal enterotoxin type A in mice is macrophage-dependent. The mechanism whereby staphylococcal enterotoxin type A stimulates macrophages to induce neutrophil recruitment remains to be elucidated.

Animals↗

PubMed1978

Escherichia coli strains that cause diarrhoea but do not produce heat-labile or heat-stable enterotoxins and are non-invasive.

Three enteropathogenic Escherichia coli (E.P.E.C.) strains (O127:K63:H6, O128:K67:H2, and O142:K86:H6) isolated from outbreaks of infantile diarrhoea and one strain from the "normal" colonic flora (E. coli HS) of a healthy adult were fed in doses of 10(6), 10(8), and 10(10) organisms in NaHCO3 to adult volunteers. The strains, which had been stored for 7--9 years, gave negative results in sensitive tests for heat-labile (L.T.) enterotoxin (Y-1 adrenal-cell test), heat-stable (S.T.) enterotoxin (infant mouse assay), invasiveness (guineapig eye test), and gross fluid accumulation (infant rabbit assay). Two strains (O142 and O127) caused diarrhoea. L.T. or S.T. enterotoxins were not found in E. coli stool isolates from individuals with diarrhoea and no one had a rise in L.T. antitoxin titre; the findings suggest that L.T. and S.T. enterotoxins were not involved in pathogenesis of the diarrhoea. Non-invasive E.P.E.C. strains probably induce diarrhoea by a mechanism (presumably an enterotoxin) distinct from L.T. or S.T. enterotoxins.

Adult↗

PubMed1997

Enterotoxin production by staphylococci isolated from foods in France.

Two hundred and thirteen Staphylococcus aureus and 51 other staphylococcal strains were isolated from 121 foodstuffs of current consumption and two cutaneous samples. Their ability to produce staphylococcal enterotoxins was tested and S. aureus strains were biotyped. The S. aureus strains (30.5%) produced at least one of the five known staphylococcal enterotoxins whereas coagulase negative staphylococci did not produce any of them. The raw milk cheeses analysed were primarily contaminated by strains belonging to animal or unspecified biovars. Only 15.9% of the S. aureus strains isolated from these products produced enterotoxins whereas 43% were found to be enterotoxigenic amongst the S. aureus strains isolated from the other foodstuffs. The scheme of biotyping used seems to be reliable, allowing the classification of 73.7% of the strains. S. aureus strains of human biovar origin were most often enterotoxigenic and enterotoxin C was the predominant type identified. It was produced by 66% of the enterotoxigenic strains, singly or in combination with other enterotoxins. Approximately 77% of the human strains also produced enterotoxin C, which is an amazing epidemiological distinctive feature of the strains studied. Moreover ELISA tests used in this work exhibit problems of specificity.

Animals↗

PubMed2003

Detection and genotyping by real-time PCR of the staphylococcal enterotoxin genes sea to sej.

This paper describes real-time fluorescence PCR assays for detecting and toxinotyping nine enterotoxin genes from Staphylococcus aureus. A universal set of primers allowed sea, seb, sec, sed, see, seg, seh, sei, sej enterotoxin genes from S. aureus to be detected in a single real-time PCR assay with the LightCycler (LC) instrument. Using the universal forward primer and a type-specific reverse primer, real-time PCR assays allowed the S. aureus enterotoxin genes to be specifically genotyped. A collection of S. aureus isolates (n=83) was detected and further characterised for sea, seb, sec, sed, see, seg, seh, sei, sej, using real-time PCR assays, and data were compared with those obtained by conventional block cycler PCR. Isolates were also tested for their ability to produce staphylococcal enterotoxins A, B, C and D by a commercial reversed passive latex agglutination (RPLA) test. Real-time PCR assays developed on the LightCycler system (LC-PCR) are a powerful tool for rapid detection and toxinotyping of the enterotoxin genes sea to sej from S. aureus. The work offers a very quick, reliable and specific alternative to conventional block cycler PCR assays to identify the enterotoxin profile of toxigenic S. aureus.

Bacterial Proteins↗

PubMed1997

IgE-binding components of staphylococcal enterotoxins in patients with atopic dermatitis.

BACKGROUND: The exacerbation of atopic dermatitis may be associated with infection of the skin with Staphylococcus aureus (S.aureus). S. aureus isolated from the skin of patients with atopic dermatitis secretes enterotoxin A, B, and toxic shock syndrome toxin 1. This is of interest because these patients may develop specific IgE antibodies against components from staphylococci. OBJECTIVE: The objective was to demonstrate IgE-sensitization to components of Staphylococcus aureus enterotoxins A and B (purified and partially purified), toxic shock syndrome toxin 1, and the bacterial cell component lipoteichoic acid, in patients with atopic dermatitis. METHODS: Blood samples from 34 patients with atopic dermatitis and 10 controls were tested by leukocyte histamine release to the enterotoxins and lipoteichoic acid. The toxins were separated by sodium dodecylsulfate polyacrylamide gel electrophoresis and analyzed by IgE-immunoblotting with sera from the same patients. RESULTS: The majority of patients (96%) with clinical signs of skin infection produced specific IgE-antibodies to all three toxins. Nearly half of the patients produced IgE to enterotoxin A and B. Only 63% of the patients with atopic dermatitis showed cellular response judged by the release of histamine from patient basophils when challenged in vitro with the toxins. This may indicate clinically unimportant sensitization in a number of patients. The immunoblotting revealed that the major allergens of the toxins were 24 and 28 kD proteins. Partially purified toxins showed a higher frequency of leukocyte histamine release responses than purified toxin. The only obvious difference was a difference in the content of pure toxin of the two preparations. Lipoteichoic acid showed nonspecific activity. CONCLUSION: These findings suggest that staphylococcal enterotoxins may act as specific allergens and induce IgE-antibodies to enterotoxins that may exacerbate the skin inflammation in some patients with atopic dermatitis.

Allergens↗

PubMed1982

Enterotoxin A and B production in strains of Staphylococcus aureus isolated from human beings and foods.

The production of enterotoxin A and B by strains of Staphylococcus aureus isolated from nasal swabs of healthy carriers, from lesions of hospital patients and from foods unconnected with outbreaks of food-poisoning was investigated. Sixty-six strains of S. aureus were obtained from human beings, two produced enterotoxin A, 45 produced enterotoxin B, seven produced enterotoxins A + B. Thirty-six strains were isolated from 111 samples of food, one produced enterotoxin A, 16 produced enterotoxin B. The relative incidence of A, B and A + B enterotoxigenicity was assessed.

Animals↗

PubMed1997

Enterotoxin and toxic shock syndrome toxin-1 production of methicillin resistant and methicillin sensitive Staphylococcus aureus strains.

In this study the production of enterotoxin A-D and toxic shock syndrome toxin-1 (TSST-1) of 181 methicillin resistant (MRSA) and 100 methicillin sensitive (MSSA) Staphylococcus aureus first isolates from different patients was investigated. All the MRSA- and MSSA isolates in the study were collected in a period between 1993 and 1995 from specimens sent from 11 different acute care hospitals in the greater Düsseldorf area. As far as possible the isolates were matched according to ward and hospital. The isolates were collected in the same time period and matched for specimen from which isolated. Furthermore, only first isolates were analysed in both groups. No significant difference in the production of toxin of any type between MRSA and MSSA could be detected (51 and 40% respectively). When the individual toxins were analysed, again no significant difference between MRSA and MSSA was demonstrable (enterotoxin production by MRSA 40% and MSSA 36%, and TSST-1 16% and 8% respectively). Despite this, a slight tendency for MRSA to produce enterotoxin A and B and for MSSA to produce enterotoxin C was observed. In addition, generation of TSST-1 by both groups was independent of enterotoxin A-D production. Interestingly, no increase in the proportion of TSST-1- or enterotoxin-producing MRSA and MSSA isolates was observed in strains isolated from blood cultures from patients with a clinical diagnosis of sepsis. Genotypical pulsed-field-gel-electrophoresis (PFGE) and phenotypical (bacteriophage typing, lysotyping) characterization of the 181 MRSA isolates resulted in 28 different PFGE patterns (of which 19 were toxin producers) and 22 lysotyping groups (18 of which produced toxin). In summary, the investigated clinical S. aureus isolates showed no difference in their ability to produce toxin and this was independent of their sensitivity to methicillin.

Bacterial Toxins↗

PubMed1995

Staphylococcal enterotoxins A and B share a common structural motif for binding class II major histocompatibility complex molecules.

A comparative site-directed mutagenesis study of staphylococcal enterotoxins A and B was undertaken to identify key amino-acid residues which govern interactions with major histocompatibility class II molecules. This involved generating a three-dimensional homology model for enterotoxin A in complex with the HLA-DR1 molecule, based on the reported X-ray crystal structures of enterotoxin B, both free and bound to HLA-DR1. A binding motif previously described for enterotoxin B was found to be conserved in enterotoxin A. An examination of the experimental data with the homology model clarifies how T-cell responses to enterotoxin A, and most bacterial superantigens, are likely to be mediated by variations of a structurally conserved HLA-DR alpha binding motif.

Amino Acid Sequence↗

PubMed2001

Staphylococcus aureus enterotoxins induce histamine and leukotriene release in patients with atopic eczema.

BACKGROUND: Chronic skin colonization with Staphylococcus aureus is a characteristic feature of atopic eczema (AE), and about 60% of S. aureus strains isolated from the skin of patients with AE secrete enterotoxins. Furthermore, IgE antibodies to S. aureus enterotoxins have been identified in 78% of patients with AE. OBJECTIVES: To examine the S. aureus enterotoxin-induced histamine and leukotriene release of basophils from patients with AE. METHODS: Peripheral blood basophils from patients with AE were stimulated with the staphylococcal enterotoxins A, B, D, E and toxic shock syndrome toxin-1. Additionally, priming experiments were performed with interleukin (IL)-3, IL-8 and granulocyte/macrophage colony-stimulating factor followed by stimulation with S. aureus enterotoxins. RESULTS: In patients with AE, basophils secreted significantly higher amounts of histamine and leukotriene C4 (LTC4) than in healthy controls. The priming experiments showed additional histamine and LTC4 release in the group of AE patients. CONCLUSIONS: Histamine and leukotriene generation from atopic basophils stimulated with staphylococcal enterotoxins may indicate a role for these toxins as possible allergens in at least a subgroup of patients with AE.

Bacterial Toxins↗

PubMed1999

Evaluation of an alternative extraction procedure for enterotoxin determination in dairy products.

A concentration protocol based on trichloroacetic acid precipitation was evaluated and compared with the reference method using dialysis concentration. Different quantities of purified staphylococcal enterotoxins were added to pasteurized Camembert-type cheeses. Detection of enterotoxins in these cheeses was performed using an automated detection system. Raw goat milk Camembert-type cheeses involved in a staphylococcal food poisoning were also tested. Both enterotoxin extraction methods allowed detection of the lowest enterotoxin concentration level used in this study (0.5 ng g-1). Compared with the dialysis concentration method, TCA precipitation of staphylococcal enterotoxins was 'user-friendly' and less time-consuming. These results suggest that TCA precipitation is a rapid (1 h), simple and reliable method of extracting enterotoxin from food which gives excellent recovery from dairy products.

Animals↗

PubMed1986

A comparative study of enterotoxin gene probes and tests for toxin production to detect enterotoxigenic Escherichia coli.

Escherichia coli isolated from children with diarrhea were tested for enterotoxin production and for hybridization with gene probes for heat-labile (LT) and heat-stable (ST-H and ST-P) enterotoxin. Fecal specimens were also examined directly for genes coding for enterotoxins. E. coli that hybridized with the cloned enterotoxin gene probes was identified by colony hybridization from 46 children, by enterotoxin production from 38 children, and by specimen hybridization from 37 of 304 children examined. Eighty-six percent (473 of 550) of E. coli that hybridized with the cloned DNA probes produced enterotoxins. Four E. coli that hybridized with the LT and 73 E. coli that hybridized with the ST-H probes were nonenterotoxigenic. These isolates were subsequently shown not to hybridize with other constructions of the same probes and did not hybridize with synthetic single-stranded oligonucleotides directed against the LT or ST genes.

Bacterial Toxins↗

PubMed1991

Staphylococcal enterotoxin microbial superantigens.

Staphylococcal enterotoxins are a family of structurally related proteins that are produced by Staphylococcus aureus. In addition to their role in the pathogenicity of food poisoning, these microbial superantigens have profound effects on the immune system, which makes them useful tools for understanding its mechanism of action. These molecules (24-30 kDa) are highly hydrophilic and exhibit low alpha helix and high beta pleated sheet content, suggesting a flexible, accessible structure. Staphylococcal enterotoxins are among the most potent activators of T lymphocytes known. The receptors for staphylococcal enterotoxins on antigen-presenting cells are major histocompatibility complex (MHC) class II molecules. Further, the alpha-helical regions of the class II molecule are essential for function and appear to interact directly with the NH2-terminal region of staphylococcal enterotoxins such as SEA. Recent studies have shown that a complex of staphylococcal enterotoxin and MHC class II molecules is required for binding to the V beta region of the T cell antigen receptor. Staphylococcal enterotoxin mitogenic activity is dependent on induction of interleukin 2, which may be intimately involved in the mechanism of toxicity. The mouse minor lymphocyte stimulating (M1s) "endogenous" self-superantigen has been shown to be a retroviral gene product, so this too is apparently a microbial superantigen. An understanding of the mechanisms of action of these microbial superantigens has implications for normal and pathological immune functions.

Animals↗