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At least 73 records · Page 4Linked to original sources
PubMed1983

Analysis of antigenic determinants in cholera enterotoxin and heat-labile enterotoxins from human and porcine enterotoxigenic Escherichia coli.

Antigenic determinants of cholera enterotoxin (CT) and heat-labile enterotoxin from a human strain (LTh) and a porcine strain (LTp) were analyzed by Ouchterlony double-gel diffusion test against anti-CT, anti-LTh, and anti-LTp, which were treated by immunoaffinity column chromatography. The results showed the existence of the following antigenic determinants: (i) antigenic determinants unique to CT, LTh, and LTp, respectively; (ii) an antigenic determinant common to CT, LTh, and LTp; (iii) an antigenic determinant common to CT and LTh, but not LTp; and (iv) an antigenic determinant common to LTh and LTp, but not CT. On the basis of these results, an antigenic scheme for CT, LTh, and LTp is proposed.

Animals↗
PubMed1992

A conjugated synthetic peptide corresponding to the C-terminal region of Clostridium perfringens type A enterotoxin elicits an enterotoxin-neutralizing antibody response in mice.

A synthetic peptide homolog corresponding to the C-terminal 30 amino acids of Clostridium perfringens type A enterotoxin (CPE) was conjugated to a thyroglobulin carrier and used to immunize mice. Conjugate-immunized mice produced antibodies which neutralized native CPE cytotoxicity, at least in part, by blocking enterotoxin binding. This peptide may be useful for the development of a vaccine to protect against CPE-mediated disease.

Amino Acid Sequence↗
PubMed1987

Fusion of Escherichia coli heat-stable enterotoxin and heat-labile enterotoxin B subunit.

The 3' terminus of the DNA coding for the extracellular Escherichia coli heat-stable enterotoxin (ST) devoid of transcription and translation stop signals was fused to the 5' terminus of the DNA coding for the periplasmic B subunit of the heat-labile enterotoxin (LTB) deleted of ribosomal binding sites and leader peptide. By RNA-DNA hybridization analysis, it was shown that the fused DNA was transcribed in vivo into an RNA species in close agreement with the expected molecular weight inferred from the nucleotide sequence. The translation products of the fused DNA resulted in a hybrid molecule recognized in Western blots (immunoblots) with antibodies directed against the heat-labile moiety. Anti-LTB antibodies coupled to a solid support bound ST and LTB simultaneously when incubated with ST-LTB cellular extracts. By [35S]cysteine pulse-chase experiments, it was shown that the fused ST-LTB polypeptide was converted from a precursor with an equivalent electrophoretic mobility of 20,800 daltons to an approximately 18,500-dalton species, which accumulated within the cell. The data suggest that wild-type ST undergoes at least two processing steps during its export to the culture supernatant. Blocking the natural carboxy terminus of ST inhibited the second proteolytic step and extracellular delivery of the hybrid molecule.

Amino Acid Sequence↗
PubMed1984

Differential detection of cholera enterotoxin and Escherichia coli heat-labile enterotoxin by enzyme-linked immunosorbent assays with antibodies specific to the two toxins.

Enzyme-linked immunosorbent assays (ELISAs) with antibodies specific to either cholera enterotoxin (CT) of Vibrio cholerae or heat-labile enterotoxin (LT) of enterotoxigenic Escherichia coli were developed to detect LT and CT, respectively. With these ELISA systems, LT and CT could be detected only with the respective specific antibody. Both antibody ELISA and ganglioside ELISA were used for differential detection of LT and CT, but the former method seemed to be more specific. By this ELISA, as little as 0.1 ng of purified LT or CT could be detected per ml. The type of toxins in fluids in intestinal loops of experimental animals challenged with living cells of either V. cholerae or LT-producing E. coli was identified correctly by this ELISA. These results suggest that the ELISA systems reported here could be used to detect and differentiate CT and LT in unknown samples; it could also be used for assaying toxins in stool specimens for the diagnosis of diarrhea due to V. cholerae or LT-producing E. coli directly, without or before bacterial isolation.

Animals↗
PubMed1978

Increased Escherichia coli enterotoxin detection after concentrating culture supernatants: possible new enterotoxin detectable in dogs but not in infant mice.

The heat-stable enterotoxin (ST) of Escherichia coli can be detected by infant mouse or dog intestinal loop tests. These tests differ in that the dog assay uses concentrated culture supernatants and is based on measurements of net intestinal absorption, whereas the mouse test uses unconcentrated supernatants and depends on gross fluid accumulation. To compare the relative sensitivities of these assays, culture supernatants of randomly selected E. coli isolates from 34 Bangalee diarrhea patients were tested for ST in dog loops and infant mice. Supernatants were also tested for heat-labile enterotoxin (LT) in dog loops, Y-1 adrenal cells, and Chinese hamster ovary cells. E. coli supernatants that produced positive responses for both ST and LT in the dog loop assay (ST+/LT+) also produced positive responses when tested for ST in infant mice and for LT in cell lines. Supernatants of strains negative for ST and LT in dog loop (ST-/LT) were also negative in other assays. Of 10 strains positive for just ST in the dog loop test (ST+/LT-), only 5 were ST positive in the standard infant mouse test. Supernatants of the other five strains (dog loop positive, mouse test negative) were then concentrated 100-fold and retested in mice. Three of these five gave consistently positive results after concentration, and two were only intermittently positive. Concentrated supernatants of negative control strains (ST-/LT-) were all negative in mice. The dog assay detects more strains producing ST than the infant mouse test. The infant mouse test, which detects only gross fluid accumulation, failed to detect approximately half of the 10 strains which produced ST alone (ST+/LT-; P = 0.025). Concentrating supernatants for the mouse assay increases sensitivity for detection of ST, but certain E. coli strains produce a variety of ST to which infant mice do not respond.

Animals↗
PubMed1983

Studies of enterotoxin of Shigella dysenteriae type 1. I. Effect of aeration on the production of enterotoxin and suitability of laboratory animals for its biological assay.

Shigella dysenteriae type 1 was used to study the influence of aeration on enterotoxin production and the suitability of laboratory animals for the toxin assay. The enterotoxin produced under aerobic shake culture conditions gave a gut dilatory response of 1.436 but that obtained in aerobic and anaerobic stationary cultures exerted no activity. The toxin fractionated on Sephadex G-150 column was more effective than that obtained by ammonium sulphate precipitation. Only Sephadex column fraction II had a toxic activity. Among the three laboratory animal models tested, the rabbit ileal loop was suitable for the assay of toxin. The skin permeability test was unsatisfactory for enterotoxicity assay.

Aerobiosis↗
PubMed1982

Klebsiella pneumoniae enterotoxin. II. Physicochemical properties of enterotoxin.

Physicochemical properties and systemic effects of the enterotoxin of Klebsiella pneumoniae has been studied. The enterotoxin had a molecular weight between 10 000 to 50 000. It was protein in nature, and heat and acid stable, inducing a dilatatory response in the gut. It haemolyzed the erythrocytes of various animals including man. It had a capillary permeability activity. In addition, when administered parenterally it increased the level of blood glucose, serum cholesterol, serum alkaline phosphatase and serum acid phosphatase.

Acid Phosphatase↗
PubMed1990

Immunosuppressive activity of staphylococcal enterotoxin B. I. Characterization of staphylococcal enterotoxin-B-induced suppressor cells.

Staphylococcal enterotoxin B (SEB) binds specifically to major histocompatibility complex class II molecules on the surface of accessory cells and stimulates virtually all T cells bearing certain, but not all, T cell-receptor V beta alleles. We have previously shown that this superantigen is a potent inducer of multiple regulatory T cell populations. In the present report we show that SEB induces a population of suppressor T cells which inhibits the generation of alloantigen-induced cytotoxic T cell activity. Using both negative- and positive-selection analysis, we found that this suppressor population is a CD4- CD8- CD5+ IL-2R+ T cell. This cell population inhibited both syngeneic and allogeneic cytotoxic T lymphocyte activity, but the cell population which inhibited allogeneic CTL activity was radiation sensitive. In addition, allogeneic SEB-primed cells appeared to develop cytolytic activity as a result of the additional stimulation in the mixed-lymphocyte reaction culture. The relationship of the SEB-primed CD4- CD8- CD5+ T cells to related regulatory T cell populations is discussed.

Animals↗
PubMed1987

Heat-stable (STa) enterotoxin of enterotoxigenic Escherichia coli: binding of the enterotoxin to coagulated milk and casein.

Oral or intragastric inoculation of the STa enterotoxin of Escherichia coli has been the standard laboratory test for that toxin. We demonstrated that the severity of the secretory response of 2-4-day-old mice to a single dose of the toxin was influenced by weaning of these mice. After oral application of 50-250 fmol of purified, radioiodinated STa toxin (12-13 Ci mmol-1) approximately 55-65% of the administered toxin bound to the stomach contents. Binding of the toxin did not destroy its biological activity. The binding was pH dependent; stomach contents bound 75% of the toxin at pH 2.3 and only 7.4% at pH 10.1. The principle in the stomach contents which bound the toxin was also demonstrated in murine and bovine milk. Further studies with renin-coagulated milk and commercial casein indicated that milk casein bound the toxin. Based on these findings, we speculate that in cases of food-poisoning involving casein-containing foods STa toxin may be present in the absence of cultivable enterotoxigenic E. coli.

Animals↗
PubMed1988

The effects of Clostridium perfringens enterotoxin on intracellular levels or transport of uridine, thymidine and leucine do not fully explain enterotoxin-induced inhibition of macromolecular synthesis in Vero cells.

Clostridium perfringens type A enterotoxin (CPE) has been shown previously to inhibit the incorporation of radiolabeled precursors into acid-insoluble material but the mechanism of inhibition is unknown. It has also been shown that extracellular calcium is required for some CPE effects. In this report, it is shown that CPE completely and virtually simultaneously inhibits incorporation of precursors into RNA, DNA and protein in either the presence or absence of extracellular divalent cations and that changes in intracellular precursor levels did not consistently correlate with this CPE-induced inhibition of incorporation. These results strongly suggest that CPE can inhibit macromolecular synthesis, not just inhibit precursor transport. It is inferred from this that CPE can affect DNA and RNA synthesis, and possibly protein synthesis, by altering other cellular processes besides, or in addition to, precursor transport and these effects then lead to a shutdown of macromolecular synthesis.

Animals↗
PubMed2001

Enterotoxin production and DNA fingerprinting in Staphylococcus aureus isolated from human and food samples. Relations between genetic types and enterotoxins.

A total of 224 Staphylococcus aureus strains from human carriers (110 strains) and manually handled foods (114 strains) collected in the Principality of Asturias, Spain over 1995-1999 were analysed for the production of enterotoxins (SEs) A, B, C, and D by a reversed passive latex agglutination test and by amplification of ent genes (A, B, C, D, E, and J) using PCR. Sixty-two strains were enterotoxigenic and a good relation between detection of SEs and their ent genes was found. No strain carried entE and all strains producing SED carried entD and entJ genes. Among the enterotoxigenic strains the percentages registered were 29, 8, 35, 18, 2, 2, and 6 for SEA, SEB, SEC, SEDJ, SEAC, SEADJ and SECDJ, respectively. DNA fingerprinting of 77 strains (the SE prototypes, 62 enterotoxigenic and 10 non-enterotoxigenic [NE]) was carried out by randomly amplified polymorphic DNA using two selected primers independently. Combining results from both primers, 10 genetic types were defined, which showed a different degree of relationship (similarity coefficient: 0.9-0.36) and were clustered into three lineages. One lineage clustered five genetic types and a wide diversity of strains, mainly SEA, SEB, SEDJ, and NE. Another lineage clustered only SEC, SECDJ and NE strains. These two lineages showed a low genetic relationship and appeared as endemic in healthy humans living in the Principality of Asturias. The third lineage included only the prototype strains for SEA and SEE.

Bacteriological Techniques↗
PubMed1994

Toxic shock syndrome toxin 1-producing Staphylococcus aureus isolates contain the staphylococcal enterotoxin B genetic element but do not express staphylococcal enterotoxin B.

Toxic shock syndrome toxin 1 (TSST-1) and staphylococcal enterotoxin B (SEB) are two examples of variable genetic traits produced by Staphylococcus aureus. Regarding phenotypes, most investigations have reported that SEB and TSST-1 are not coproduced in S. aureus. However, it is unclear whether genotypically SEB (entB) and TSST-1 (tst) genes are found within the same isolate. Gene probes specific for entB and tst showed that both genes were present within 8 TSST-1+ isolates analyzed. However, SEB was not produced by any of these isolates. In contrast, none of 9 SEB-producing S. aureus isolates contained the TSST-1 genetic element DNA. Hybridization of restriction fragments with TSST-1 and SEB genetic element probes and tryptophan auxotyping suggested that tst and entB are located in close proximity on the chromosome. The entB locus may be a preferred site of insertion for the TSST-1 genetic element, and such insertion may interfere with the expression of SEB.

Bacterial Toxins↗
PubMed1993

Fusion of the genes encoding Escherichia coli heat-stable enterotoxin b (STb) and the maltose-binding protein to obtain mature STb enterotoxin.

The heat-stable enterotoxin b gene (estB) of Escherichia coli was fused to the gene for maltose-binding protein (malE). The estB gene was cloned into the pMAL-p vector using PCR. The construct consists of the signal sequence of maltose-binding protein, which directs the export of the fusion protein to the periplasm, and the maltose-binding protein fused to the STb polypeptide. A sequence encoding a factor Xa cleavage site is present between malE and estB. The fused genes are controlled by Ptac, a strong inducible promoter. Following IPTG induction, the recombinant strain expressed a 47 kDa protein, which was easily purified from osmotic shock fluid by using preparative electrophoresis and electroelution. Cleavage of the fusion protein with factor Xa generated the maltose-binding protein (42 kDa) and a polypeptide of approximately 5 kDa, corresponding to the molecular mass of mature STb. A monospecific polyclonal rabbit antiserum raised against purified STb reacted in immunoblot with the fusion protein and the cleaved-off peptide. A positive response was observed when testing the osmotic shock fluid containing the fusion protein in a rat intestinal loop assay. On average, 3-4 mg of MBP-STb protein was recovered per litre of induced recombinant strain.

ATP-Binding Cassette Transporters↗
PubMed1982

Development of a vaccine of cross-linked heat-stable and heat-labile enterotoxins that protects against Escherichia coli producing either enterotoxin.

A vaccine of cross-linked heat-stable (ST) and heat-labile (LT) toxins that protects against heterologous serotypes of strains of Escherichia coli which produce either the LT or ST enterotoxin was developed by conjugating ST to LT by the carbodiimide reaction. Three interrelated factors were found to affect the composition and properties of the final conjugate: (i) the amount of carbodiimide added to the toxins, (ii) the initial ratio of ST to LT, and (iii) the duration of the conjugation reaction. Optimal conjugation conditions were identified as a carbodiimide-to-toxin ratio of 10:1 by weight, an initial molar ratio of ST to LT of 100:1, and a conjugation reaction time of 96 h. This approach yielded a conjugate that contained 96% by moles and 36% by weight pure ST, determined with radioiodinated pure ST, and 34% by weight semi-pure ST, determined by the Lowry protein method. The retained antigenicities of the conjugated toxins, as determined by enzyme-linked immunosorbent assays, was greater than or equal to 82%, and their toxicities, as determined by the Y1 adrenal cell assay for LT and by the suckling mouse assay for ST, were reduced to less than or equal to 0.15%. Immunization of rats with this cross-linked ST-LT vaccine provided strong protection against challenge with either the LT or the ST toxin or with viable heterologous strains which produce these toxins, either singly or together. These observations indicate that conjugation of ST to LT results in a unique new immunogen in that ST acquires immunogenicity as a function of the reaction, LT retains most of its antigenicity, and the toxic properties of each individual toxin are greatly reduced.

Animals↗
PubMed1993

Assessment of enterotoxin production by Yersinia enterocolitica and identification of a novel heat-stable enterotoxin produced by a noninvasive Y. enterocolitica strain isolated from clinical material.

Twenty-eight clinical isolates of Yersinia enterocolitica were investigated for their abilities to produce heat-stable enterotoxin (YST). All 21 invasive strains (serogroup O3 biotype 4) carried the previously described gene for YST (yst), with toxin detectable in culture supernatants from 20 strains. One of seven noninvasive, biotype 1A strains also had enterotoxic activity, despite failure to hybridize with a probe for yst. The toxin produced by this noninvasive (serogroup O6) strain resembled YST in terms of molecular size, heat stability, and solubility in methanol. It differed from YST, however, with respect to regulation of its production by temperature and its mechanism of action, which did not appear to involve cyclic GMP.

Animals↗
PubMed2003

Development of a duplex PCR genotyping assay for distinguishing Clostridium perfringens type A isolates carrying chromosomal enterotoxin (cpe) genes from those carrying plasmid-borne enterotoxin (cpe) genes.

About 5% of Clostridium perfringens type A isolates carry the cpe gene encoding the C. perfringens enterotoxin. Those cpe-positive type A isolates are important causes of food-poisoning and non-food-borne cases of diarrheas in humans, as well as certain veterinary cases of diarrhea. Previous studies have determined that the enterotoxigenic type A isolates causing both non-food-borne human gastrointestinal disease and veterinary disease carry their cpe genes on plasmids, while the type A isolates causing human food poisoning carry a chromosomal cpe gene. The present study reports on the successful development of a duplex PCR assay that can rapidly genotype enterotoxigenic type A isolates (i.e., determine whether those cpe-positive isolates carry a chromosomal or a plasmid-borne cpe gene). The availability of this rapid cpe genotyping assay capable of handling large numbers of samples provides a powerful new investigative tool for diagnostic, epidemiologic, and basic research purposes.

Bacterial Typing Techniques↗
PubMed1987

Purification of heat-labile enterotoxin from an enterotoxin from an enterotoxigenic Escherichia coli of human origin by monoclonal immunoaffinity chromatography.

Heat-labile enterotoxin (LT) was purified from an enterotoxigenic Escherichia coli 015H11 of human origin. The purification steps included French pressure cell disruption of the bacteria, salting-out, DEAE-Sephacel on chromatography. Application of this procedure resulted in a 95.1-fold purification of LT with a yield of 19.9% as determined by rabbit ileal loop assay. The final LT preparation showed only one protein-staining band on polyacrylamide gel electrophoresis, indicating that the purified LT was homogeneous.

Animals↗