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PubMed1989

Purification and partial characterization of a cytotonic enterotoxin produced by Aeromonas hydrophila.

This report describes the purification and partial characterization of a cytotonic enterotoxin produced by a human diarrheal isolate (SSU) of Aeromonas hydrophila. The extracellular enterotoxin was purified by (NH4)2SO4 precipitation, hydrophobic column chromatography, and chromatofocusing. The highly purified enterotoxin exhibited a molecular mass of 44 kDa and an isoelectric point in the range of 4.3 - 5.5 as determined by chromatofocusing. Western blot analysis using Aeromonas anti-enterotoxin revealed a single band at 44 kDa; however, cholera antitoxin failed to detect the enterotoxin antigen. This non-cholera toxin cross-reactive (non-CTC) enterotoxin was biologically active in vivo as determined by rabbit ligated ileal loop and rabbit skin vascular permeability assays. Biological activity also was in vitro by this toxin as measured by the elongation of Chinese hamster ovary (CHO) cells. The enterotoxic activity associated with this molecule was neutralized completely by homologous antibodies but not by cholera antitoxin. The purified toxin preparation was free of hemolytic and cytotoxic activities as determined by its inability to lyse rabbit red blood cells or damage CHO cells, respectively. Furthermore, this toxin induced the elevation of cAMP in CHO cells suggesting thereby that the mechanism of action of Aeromonas non-CTC enterotoxin may be similar to heat-labile enterotoxins of Escherichia coli and Vibrio cholerae.

Aeromonas↗

PubMed2005

Staphylococcal enterotoxin and its rapid identification in foods by enzyme-linked immunosorbent assay-based methodology.

The problem of Staphylococcus aureus and other species as contaminants in the food supply remains significant on a global level. Time and temperature abuse of a food product contaminated with enterotoxigenic staphylococci can result in formation of enterotoxin, which can produce foodborne illness when the product is ingested. Between 100 and 200 ng of enterotoxin can cause symptoms consistent with staphylococcal intoxication. Although humans are the primary reservoirs of contamination, animals, air, dust, and food contact surfaces can serve as vehicles in the transfer of this pathogen to the food supply. Foods may become contaminated during production or processing and in homes or food establishments, where the organism can proliferate to high concentrations and subsequently produce enterotoxin. The staphylococcal enterotoxins are highly heat stable and can remain biologically active after exposure to retort temperatures. Prior to the development of serological methods for the identification of enterotoxin, monkeys (gastric intubation) and later kittens (intravenous injection) were used in assays for toxin detection. When enterotoxins were identified as mature proteins that were antigenic, serological assays were developed for use in the laboratory analysis of foods suspected of containing preformed enterotoxin. More recently developed methods are tracer-labeled immunoassays. Of these methods, the enzyme-linked immunosorbent assays are highly specific, highly sensitive, and rapid for the detection of enterotoxin in foods.

Enterotoxins↗

PubMed2002

Detection of staphylococcal enterotoxin B (SEB) by enzyme-linked immunosorbent assay and by a rapid hand-held assay.

Staphylococcal enterotoxins are a frequent cause of food poisoning. Immunologically-based assays for the detection of staphylococcal enterotoxins are commercially available, but require at minimum of 3 hours. We used staphylococcal enterotoxin B to compare two commercially available assays with a newly developed rapid immunochromatographic-based hand-held assay. The detection limit of the commercially available assays accounted for 500 pg and 100 pg enterotoxin B/ml, respectively, whereas 50 pg enterotoxin B /ml were detected within 15 min using the hand-held assay. Enterotoxin B-spiked custard served as a model to detect staphylococcal enterotoxin in food. Depending on the extraction method applied, the detection limit was in the range of 500 pg to 2500 pg/g custard for the commercially available assays and 62.5 pg/g for the hand-held assay. We conclude that the hand-held assay is widely applicable because it is sensitive, specific with regard to the tested enterotoxins, and the results can be read with the naked eye.

Enterotoxins↗

PubMed1986

Production of enterotoxins by strains of Escherichia coli isolated from pigs.

The production of enterotoxins by 237 hemolytic strains of Escherichia coli isolated from pigs was determined with the use of CTE in CHO. Vero and Hela cells and ILT. More frequent (p less than 0.01) production of enterotoxins, determined by ILT, was found for the serotypes being pathogenic for the animals (63.8% of the strains). No correlation between intensity of ILT and particular serotype was observed. Both the serotypes pathogenic for pigs and other serotypes produced LT enterotoxins and ST toxin. The frequency of LT enterotoxin production was statistically insignificant compared to the frequency of ST enterotoxin production by strains with serotypes pathogenic for the pigs. Strains of E. coli producing only enterotoxin ST belonged both to the pathogenic serotypes as well as to other hemolytic serotypes. The cytotoxic activity of supernatants of E. coli strains with different serotypes isolated from pigs in Vero and Hela cells and simultaneous CTE in CHO cells was observed. This suggests the production by the strains of enterotoxin LT and cytotoxin VT. Seven out of the 96 isolates showing CTE in CHO cells gave no reaction in the ILT in pigs. This suggests the production by these isolates of a toxin (toxins) differing from the E. coli enterotoxins.

Animals↗

PubMed1983

Differences in bindings to the GM1 receptor by heat-labile enterotoxin of human and porcine Escherichia coli strains.

Heat-labile enterotoxin producing strains of Escherichia coli were isolated from diarrheal faeces of humans and from the jejunum of pigs which had died of diarrhea. The heat-labile enterotoxin was assayed by three different enzyme-linked immunosorbent assays (ELISA). The first assay was based upon immunological cross-reactions between the heat-labile enterotoxins of E coli and Vibrio cholerae, the second on specific E coli heat-labile enterotoxin antibodies and the third on affinity of the toxin to the presumed cell membrane receptor, the ganglioside GM1. The heat-labile enterotoxins of human and porcine origin bound equally well to the same extent in the ELISA procedure, which utilized immunological cross-reactivity between the heat-labile enterotoxins of E coli and V cholerae. The reactivity, however, was quite different in the GM1-ELISA. The binding affinity was high between GM1 and enterotoxin produced by E coli strains of human origin, whereas the binding affinity was low for enterotoxin from porcine strains.

Animals↗

PubMed1984

[Detection of staphylococcal enterotoxin by latex agglutination inhibition test].

Latex agglutination inhibition test was developed for the detection of staphylococcal enterotoxin. Water soluble carbodiimide was used for coupling enterotoxin to latex particles. Test samples were added to the anti-enterotoxin serum at first. Then, enterotoxin-linked latex particles were added to the mixture. When enterotoxin was present in the test sample, it reacted with anti-enterotoxin antibodies and inhibited antitoxin to agglutinate enterotoxin-linked latex particles. The inhibition of latex agglutination resulted in tho formation of sedimentation in the button of the well of microtiter or microcentrifuge tube. The test was read after 8 hours or overnight incubation at room temperature and the concentration of staphylococcal enterotoxin B as low as 0.5 micrograms/ml could be detected.

Enterotoxins↗

PubMed1982

Inhibitory effect of indomethacin on skin permeability reactions mediated by heat-labile enterotoxins of Salmonella weltevreden, Escherichia coli and Vibrio cholerae.

Indomethacin, a rapid and intense inhibitor of prostaglandin synthesis, was used with a view to find out similarity in secretory mechanism of heat-labile enterotoxins of three diarrhoea producing enteric bacteria viz., Salmonella weltevreden, Escherichia coli and Vibrio cholerae in rabbits. A significant inhibition (90% to 94%) of biological activity of indomethacin pretreated Salmonella enterotoxin was evident in indomethacin treated rabbits, whereas the biological activity was found comparatively low (28% to 76%) in the untreated enterotoxin preparations. In contrast, the skin permeability reaction to cholera toxin remained unaltered in the absence of pretreatment of cholera toxin with indomethacin and it dropped to 55% in pre-treated toxin preparations. There was complete inhibition of biological activity of E. coli enterotoxin which did not receive indomethacin pretreatment. Based on these observations it may be inferred that indomethacin inhibits skin permeability response of heat labile enterotoxin of S. weltevreden both by blocking the effect of prostaglandins (Blocking mechanism) as well as by prostaglandin-adenyl cyclase pathway. The reduction in the biological activity of cholera toxin seems to be occurring through blocking of prostaglandins by indomethacin. In case of E. coli enterotoxin the inhibition mechanism seems operating through prostaglandin-adenyl cyclase system. These observations indicate that the Salmonella enterotoxin shares some similarity with enterotoxins of E. coli and Vibrio cholerae in respect of mechanism of action.

Animals↗

PubMed1982

Enterotoxin production by Staphylococcus aureus strains isolated from humans, foods and animals in Malaysia.

Enterotoxin production by strains of Staphylococcus aureus isolated from human, food and animal sources was investigated. Of the 130 isolates studied, 27 (20.8%) were found to be enterotoxigenic. The most common enterotoxin detected from human sources was enterotoxin C whereas enterotoxin B occurred more frequently in staphylococcal strains of food origin. The 2 enterotoxigenic strains, from animals isolated from a dog and a goat, produced enterotoxins A and C, respectively. Enterotoxin E was not detected alone from any of the enterotoxigenic strains studied, but occurred together with other enterotoxins. The need to detect enterotoxin in staphylococcal strains and in suspected foods for the confirmation of staphylococcal food poisoning is discussed.

Animals↗

PubMed1996

Staphylococcal enterotoxin B applied on intact normal and intact atopic skin induces dermatitis.

BACKGROUND AND DESIGN: Colonization of inflammatory skin diseases with Staphylococcus aureus is a frequent phenomenon and may cause exacerbation of the skin disease. Staphylococcus aureus strains present on atopic dermatitis are capable of releasing staphylococcal enterotoxins, a group of superantigens that are very potent T-cell activators. To determine whether the superantigen staphylococcal enterotoxin B can induce inflammation when applied on the skin, staphylococcal enterotoxin B was applied with and without occlusion on the volar aspect of the skin on the forearm of 10 subjects without skin disease and six subjects with atopic dermatitis of minimal activity and no eczema on the volar aspect of the skin on their forearm. The main outcome measures were clinical rating; determination of the increase of the thickness of the skin-fold; and determination of skin blood flow. RESULTS: Clinically, staphylococcal enterotoxin B induced skin changes of erythema and induration in 10 of 10 healthy volunteer subjects and six of six subjects suffering from atopic dermatitis, while the vehicle induced clinically evident skin changes in only one of 10 healthy subjects and none of six subjects with atopic dermatitis. On day 3 after the application of an occluded patch containing 10 micrograms/cm2 of staphylococcal enterotoxin B in the healthy subjects, the thickness of the skinfold increased 0.47 +/- 0.49 mm (mean +/- SD) (n = 9; P < .02) relative to the increase in the thickness of the skinfold following application of the vehicle. The Doppler laser-measured skin blood flow index had increased from 1.0 +/- 0.4 to 5.3 +/- 3.7 (mean +/- SD) (n = 10; P < .002). On day 3 after the application of occluded patchs containing 10 micrograms/cm2 of staphylococcal enterotoxin B in the subjects suffering from atopic dermatitis, the increase in the thickness of the skinfold increased 0.20 +/- 0.24 mm (n = 6; P, not significant) relative to the increased thickness in the skinfold following application of the vehicle. The Doppler laser-measured skin blood flow index had increased from 1.1 +/- 0.4 to 3.7 +/- 2.2 (n = 6, P, not significant). Three of six subjects suffering from atopic dermatitis experienced a flare of their disease in the elbow flexure ipsilaterally to where the staphylococcal enterotoxin B patch was applied. CONCLUSIONS: The superantigen staphylococcal enterotoxin B applied on intact skin from both normal subjects and patients with atopic dermatitis induces an inflammatory reaction. This finding suggests that superantigens released from S aureus present on the skin in inflammatory skin diseases may exacerbate and sustain the inflammation.

Adult↗

PubMed1996

A high molecular weight protein from Staphylococcus intermedius cross-reacts with Staphylococcus aureus enterotoxin antibodies.

Enterotoxin production by Staphylococcus species other than Staphylococcus aureus has been reported. Staphylococcus strains (104 in toto) representing twelve species and subspecies were examined for enterotoxins using a commercial staphylococcal enterotoxin ELISA immunoassay (TECRA, International Bioproducts). Staphylococcus intermedius (24 strains) and S. aureus (7 strains) were positive with this test. Western blots of S. aureus exoproteins demonstrated proteins of approximately 30 kD, consistent with known staphylococcal enterotoxins. The major antigen in all S. intermedius strains, a 75 kD protein, was not analogous to previously described staphylococcal enterotoxins. This protein was unique to S. intermedius. Gel filtration data indicate that the protein is a subunit of a larger protein in vivo. The 75 kD protein cross-reacts with several enterotoxin antibodies. It is unclear whether the protein is a toxin, but its homology with S. aureus enterotoxins may indicate a shared toxic region, or this protein may create false positive results in screening for enterotoxin.

Antibodies, Bacterial↗

PubMed1990

Autoradiographic demonstration of specific binding sites for E. coli enterotoxin in various epithelia of the North American opossum.

In the North American opossum, heat-stable specific binding sites for E. coli enterotoxin are observed (i) in epithelial cells lining the small intestine, colon, gall bladder, cystic duct, common bile duct and trachea, and (ii) in epithelial cells forming the duodenal (Brunner's) glands, liver, kidneys (metanephros, mesonephros) and testis, as demonstrated by autoradiography. Enterotoxin-specific binding sites in the intestinal tract are only found in intestinal epithelial cells with the highest concentration in the microvillus border. Enterotoxin-specific binding sites also occur in epithelial cells comprising the secretory tubules and ducts of the duodenal glands. In the kidneys (metanephros and mesonephros), enterotoxin-specific binding sites are confirmed primarily to the proximal tubules, whereas in the testis they are localized in seminiferous tubules. In the liver, enterotoxin-specific binding sites are confined primarily to hepatocytes. E. coli enterotoxin caused a 7-fold increase of cGMP in the liver and a 30-fold increase in the duodenal glands. The liver responded in about half of the animals studied, whereas the duodenal glands gave a consistent response in each case. Likewise, the duodenal glands consistently showed strong labelling for 125I-enterotoxin, whereas receptor labelling of hepatocytes was inconsistent in nearly half the incubations and corresponds to the observed cGMP measurements.

Animals↗

PubMed1982

Production of enterotoxin by Escherichia coli at four, twenty-two and thirty-seven degrees centigrade.

One hundred and seventy-seven Escherichia coli strains isolated from food, pigs and humans were tested for the production of heat-labile and heat-stable enterotoxin at 4, 22, and 37 degrees C. Heat-labile enterotoxin was detected in culture supernatants by an enzyme-linked immunosorbent assay, and heat-stable enterotoxin by the infant mouse bioassay. Thirty strains produced heat-labile enterotoxin, and twenty heat-stable enterotoxin. None of the strains isolated from food were enterotoxigenic. Fifty-seven per cent of the human and porcine strains producing heat-labile enterotoxin at 37 degrees C also produced the toxin at 4 degrees C. The fact that Escherichia coli enterotoxin may be present in food at consumption must be considered pathogenetically relevant.

Animals↗

PubMed1978

Isolation of the membranes of an enterotoxigenic strain of Escherichia coli and distribution of enterotoxin activity in different subcellular fractions.

The intracellular localization of enterotoxin in Escherichia coli AP1, a strain of porcine origin which produces high levels of heat-labile, but no heat-stable enterotoxin, has been examined. The cytoplasmic and outer membranes of this strain both contained enterotoxin activity, while the membranes isolated from a serologically related non-enterotoxigenic strain (E. coli AP2) also of porcine origin, did not show enterotoxin activity. The periplasmic fraction isolated from the enterotoxigenic strain contained considerable enterotoxin activity, but this activity was associated with outer membrane fragments present in the periplasmic fraction. Thus, of the total cellular enterotoxin activity, about 55%, 15% and 30% were present in the outer membrane, cytoplasmic membrane and the cell cytoplasm, respectively. The specific activity of enterotoxin was 20 units per mg protein in the cytoplasm and 90 and 150 units per mg protein in the cytoplasmic and outer membranes, respectively.

Biological Assay↗

PubMed1980

Characterization of membrane permeability alterations induced in Vero cells by Clostridium perfringens enterotoxin.

Alterations in plasma membrane permeability induced by Clostridium perfringens enterotoxin were studied using Vero (African green monkey kidney) cells which were radioactively labeled with four markers of different molecular size. The markers were alpha-amino[14C]isobutyric acid (Mr 103), 3H-labeled nucleotide (Mr approx. 300), 51Cr label (Mr approx. 3000) and [3H]RNA (Mr>25000). Over a 2h period, enterotoxin caused significant release of aminoisobutyric acid, nucleotides and 51Cr label but not RNA. The effects of enterotoxin on label release were dose- and time-dependent. The rate of release of markers was dependent upon their size. Permeability alterations could be detected within 15 min with a high dose of enterotoxin. Gel chromatography of released material was used to determine that markers of Mr 3000 but not 25000 leaked from permeabilized cells. It was concluded that enterotoxin is producing functional 'holes' of limited size in the membrane. Permeability changes due to enterotoxin treatment differed between confluent and nonconfluent (growing) cells. We propose that the primary action of the enterotoxin is to interact with the plasma membrane and produce functional 'holes' of defined size. The resultant alterations in membrane permeability cause the loss of essential cellular substances which inhibits processes such as macromolecular synthesis and eventually leads to cell deterioration and death.

Aminoisobutyric Acids↗

PubMed1984

Osmotic stabilizers differentially inhibit permeability alterations induced in Vero cells by Clostridium perfringens enterotoxin.

Using a sensitive Vero (African green monkey kidney) cell model system, studies were performed to further investigate whether Clostridium perfringens enterotoxin acts via disruption of the colloid-osmotic equilibrium of sensitive cells. Enterotoxin was shown to cause a rapid loss of intracellular 86Rb+ (Mr approx. 100) with time- and dose-dependent kinetics. The enterotoxin-induced release of intracellular 86Rb+ preceded the loss of two larger labels, 51Cr label (Mr approx. 3500) and 3H-labeled nucleotides (Mr less than 1000). The osmotic stabilizers, sucrose and poly(ethylene glycol), differentially inhibited enterotoxin-induced larger label loss versus 86Rb+ loss. Further, enterotoxin was shown to cause a rapid influx of 24Na+ that was not significantly inhibited by osmotic stabilizers. Additional studies demonstrated that lysosomotropic agents were not protective against characteristic enterotoxin-induced membrane permeability alterations or morphological damage. Taken collectively, these results are consistent with an action for enterotoxin which involves a disruption of the osmotic equilibrium.

Animals↗

PubMed1991

Pathodynamics of intoxication in rats and mice by enterotoxin of Clostridium perfringens type A.

The pathodynamics of lethal intoxication in rats and mice by i.v. administration of enterotoxin of Clostridium perfringens type A was studied using whole animals and isolated organs. A lethal i.v. dose (50 micrograms/kg) of enterotoxin killed anesthetized rats and mice within 4-15 min. Rapid changes of ECG pattern suggestive of hyperpotassemia, rapid fall of blood pressure and transient hyperpnea followed by respiratory depression were observed. Analysis of plasma levels of cations revealed hyperpotassemia in both animal species. On the other hand, enterotoxin (up to 100 micrograms) showed little direct cardiotoxicity on the isolated heart. ECG changes produced by i.v. injection of KCl (0.5 ml of 50 mM) mimicked the ECG changes observed in the intoxicated rats injected with a lethal dose of enterotoxin. Perfusion of rat isolated organs showed that potassium concentration in the eluent from the liver (but not lungs or lower extremities) increased markedly within 1-2 min after the administration of enterotoxin. The amount of potassium liberated from a rat liver was about 133 mumoles, which is sufficient to increase the plasma level of potassium to more than 10 mM. In addition to potassium, cytoplasmic enzymes, such as glutamate oxalacetate transaminase, glutamate pyruvate transaminase and lactate dehydrogenase, were also liberated from the intoxicated liver, indicating that potassium was liberated from hepatocytes by the change in membrane permeability produced by enterotoxin. It is concluded that hyperpotassemia elicited by the cytotoxic action of enterotoxin on hepatocytes caused cardiac failure leading to the death of the intoxicated animals.

Animals↗

PubMed1986

Effects of Ca2+ and other cations on the action of Clostridium perfringens enterotoxin.

We investigated the role of extracellular Ca2+ in the Clostridium perfringens enterotoxin-induced alteration of the permeability of the plasma membrane. Enterotoxin released 86Rb and 51Cr from the Vero cells preloaded with the isotope. In the presence of EGTA, however, it released 86Rb but not 51Cr. The binding of enterotoxin to the cells was not influenced by Ca2+ or Mg2+. The effects of various cations on the enterotoxin-induced 51Cr release was also studied. The release depended on extracellular Ca2+ but not on Mg2+; it was inhibited by each of Zn2+, La3+ and Co2+. Zn2+ and Co2+ also inhibited 51Cr release caused by the enterotoxin previously bound to the cell membrane. In contrast, antibody against enterotoxin did not neutralize the toxin once it was bound to the Vero cells. When the cells were treated with enterotoxin, 45Ca influx occurred and reached the plateau in a few minutes, as did 86Rb release.

Animals↗

PubMed1990

The use of DNA probes for confirming enterotoxin production by Staphylococcus aureus and micrococci.

DNA-DNA colony hybridization was employed to evaluate the results obtained by different immunological methods for detection of staphylococcal enterotoxin. Staphylococcus aureus strains tested for staphylococcal enterotoxin production by immuno-assays and micrococci not previously tested for staphylococcal enterotoxin production were examined for presence of the genes encoding for staphylococcal enterotoxin A, B, C and E by using three corresponding DNA probes. The staphylococcal enterotoxin A probe also detected staphylococcal enterotoxin E gene because of 100% homology. The optimal sensitivity plate method showed the best accordance between the immuno-assay and the hybridization reactions. The enzyme-linked immunosorbent assay detected 12.5 to 17% staphylococcal enterotoxin producers without hybridization reactions. The microslide gel double diffusion test and the reversed passive latex agglutination test showed rather poor accordance with the hybridization reactions. All 17 strains of different micrococci investigated were negative in hybridization with all three DNA probes.

Base Sequence↗