SEARCH · PubMed Health

Results for “ENTEROTOXINS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,027 records · Page 57Linked to original sources

PubMed1982

Evaluation of a defined medium for the production of both thermolabile (LT) and thermostable (ST) enterotoxins of Escherichia coli.

The production of thermolabile (LT) enterotoxin was compared in a defined medium reported by Staples et al. (SAG medium) for the production of thermostable (ST) enterotoxin and the Casamino acids-Yeast extract (CAYE) medium. Aliquots were drawn frum cultures of an enterotoxigenic (LT+, ST+) E. coli in both media at different times, growth curves were plotted, and culture filtrates tested for toxin activity. Levels of LT and ST and in the SAG showed that it is as suitable as CAYE for the production of LT. The addition of either glucose (1%) or lincomycin (90 microgram/ml) to SAG medium increased LT levels, but no synergistic effort could be observed if both substances were added concomitantly. Cultures in SAG medium incubated stationarily for 72 h at 37 degrees C yielded more LT than shaking cultures incubated similarly.

Animals↗

PubMed2006

Real-time fluorogenic PCR assays for the detection of entA, the gene encoding staphylococcal enterotoxin A.

Staphylococcal enterotoxin A (SEA) is among the most potent of the growing list of known enterotoxins produced by Staphylococcus aureus. SEA, a 27 kDa monomeric protein, is encoded by the entA gene. We have developed two real-time fluorogenic PCR assays for the detection of nucleic acid sequences in entA. The assays are useful in detecting and identifying strains of S. aureus that produce SEA and can serve a confirmatory role in determining the presence of SEA in food samples. The assays were tested in two real-time PCR formats, using either dye-labeled DNA probes corresponding to each primer set that are degraded by the 5' exonuclease activity of Taq polymerase, or a PCR master mix that contains the DNA-binding dye SYBR Green. In both formats the assays have a limit of detection of between 1 and 13 copies of a S. aureus genome that contains a copy of entA. Neither assay cross-reacted with genomic DNA isolated from other strains of S. aureus or other species.

Bacteriological Techniques↗

PubMed2006

Staphylococcal enterotoxin B initiates protein kinase C translocation and eicosanoid metabolism while inhibiting thrombin-induced aggregation in human platelets.

Staphylococcal enterotoxin (SE) B, a heat-stable toxin secreted by Staphylococcus aureus, has been implicated in the pathogenesis and exacerbation of several critical illnesses. It has been hypothesized that enterotoxins may interact with blood products such as platelets, in addition to T-lymphocytes and renal proximal tubule cells. The aim of this present study was to elucidate whether SEB directly alters human platelet function. Human platelet rich plasma (PRP) was pre-incubated with SEA, SEB, SEC or TSST-1, (at various concentrations and incubation times). After incubation, PRP was exposed to thrombin and aggregation was assessed. Incubation with all toxins tested resulted in decreased aggregation, specifically; exposure to 10mu g/ml of SEB for 30 min caused a 20% decrease and a 49% decrease at 90 min. A similar reduction in aggregation was seen in samples incubated with phorbol myristate acetate, a known stimulator of protein kinase C (PKC). Further, platelets exposed to SEB exhibited an increased plasma membrane PKC activity. Sphingosine, an inhibitor of PKC proved to block the SEB-induced reduction in aggregation. SEB effects on platelet metabolism were investigated using high performance liquid chromatography showing up to a 2-fold increase of active metabolites lipoxin A4 and 12-HETE, as compared to control. These data indicate that SEB is able to induce platelet dysfunction, and these effects may be mediated through activation of PKC.

Arachidonic Acid↗

PubMed1985

Biological and immunological characteristics of 125I-4Tyr and -18Tyr Escherichia coli heat-stable enterotoxin species purified by high-performance liquid chromatography.

A rapid procedure for the separation of Escherichia coli heat-stable enterotoxin iodination products is described. A two-step procedure using reverse-phase chromatography results in the separation of native, noniodinated heat-stable enterotoxins from several distinctly iodinated species which differ in their ability to bind to brush border receptors. Sequence analysis of the radioligands demonstrated mutually exclusive labeling at the 4Tyr and 18Tyr residues. These tracers have been immunologically and biologically characterized and have been shown to be antigenically similar but to differ in their toxicity for suckling mice. The radioligands separated by this procedure demonstrate stable behavior for a period of months.

Amino Acid Sequence↗

PubMed1984

Primary structure of heat-stable enterotoxin produced by Yersinia enterocolitica.

A heat-stable enterotoxin was isolated and purified from the culture supernatant of Yersinia enterocolitica by reversed-phase high-performance liquid chromatography. The amino acid sequence of the purified toxin was determined to be as follows: (sequence; see text) (X: not determined). The C-terminal sequence containing 6 half-cystine residues was highly homologous to that of heat-stable enterotoxin of enterotoxigenic Escherichia coli.

Amino Acid Sequence↗

PubMed1989

T lymphocyte activation by staphylococcal enterotoxins: role of class II molecules and T cell surface structures.

The enterotoxins produced by Staphylococcus aureus (SE) are the most potent mitogens known. Triggering of proliferation or cytotoxicity by SE requires the presence of MHC class II molecules on accessory or target cells. In this study we have investigated the role of HLA class II molecules in the activation of human T cells by SE and the nature of the target structure on the responding T lymphocyte for SE. This dependence on class II molecules is not due to an immunological "recognition" of SE since there is no restriction by polymorphic determinants of HLA molecules and since even xenogeneic class II molecules can reconstitute the human T cell response to SE. Furthermore, HLA class II-positive but not -negative cells absorb the mitogenic activity from SE solutions and significant binding of 125I-labeled SE can be demonstrated to class II-positive but not to class II-negative cells. Enterotoxin molecules react directly with T cells since they cause an increase in cytosolic Ca2+ concentration similar to anti-CD3 mAb. This increase is abrogated by prior modulation of the TCR/CD3 complex. Antibodies to CD2, CD3 and the TCR that block antigen-specific activation also block T cell activation by SE. Moreover, preincubation of purified resting accessory cell-free T cells with SE leads to modulation of the TCR/CD3 complex. Taken together these data indicate that SE interact selectively with HLA class II molecules on accessory or target cells and with a TCR-associated structure on the T cell.

Animals↗

PubMed1990

Staphylococcal enterotoxins direct and trigger CTL killing of autologous HLA-DR+ mononuclear leukocytes and freshly prepared leukemia cells.

Attempts have been made to induce cytolytic T cells to kill target cells that do not express the appropriate target molecules by crosslinking the T cells and the target cells in various ways. One successful strategy has been to use heteroconjugates or bispecific monoclonal antibodies reacting with T cell molecules with activating properties (e.g., mab directed to CD3/TCR) and target cell surface antigens. In this report we show that Staphylococcal enterotoxins (SE) direct human T lymphocytes to execute cytotoxicity toward MHC class II-expressing Raji cells, but not against MHC class II-deficient Raji mutant RJ 2.2.5. Both HLA-DR+ and HLA-DR- effector T lymphocytes are effective in the killing of Raji cells coated with SE. The Staphylococcal enterotoxin-dependent cell-mediated cytotoxicity (SDCC) is a rapid T lymphocyte-mediated cytolytic mechanism killing the targets within an hour of incubation. HLA-DR+ target cells are sensitized to be killed within minutes of incubation with picomolar concentrations of SE. SE-sensitized Raji cells remain targets for SDCC after overnight culture at 37 degrees C, demonstrating that the sensitive state is relatively stable. SEA- and SEB-selective cytolytic T cell lines were established to illustrate the clonal variability of SDCC effectors with respect to SE specificity. We also demonstrate that autologous monocytes and activated T lymphocytes as well as B lymphocytes and freshly prepared HLA-DR+ leukemic cells are excellent targets in SDCC.

B-Lymphocytes↗

PubMed1984

Preparation of isolated liver endothelial cells and Kupffer cells in high yield by means of an enterotoxin.

A new method for preparing non-parenchymal rat liver cells (NPC) is described. The liver cell suspension, prepared by perfusing the liver with collagenase, was treated with enterotoxin from Clostridium perfringens for 15 min. The enterotoxin made the parenchymal cells leaky, and these cells could be separated from the NPC by centrifugation in a solution containing Nycodenz (20%, w/v). During the centrifugation, the NPC floated, while the parenchymal cells sedimented. The yield of NPC per liver (200 g rat) was about 250 X 10(6) cells. The NPC were further separated into endothelial cells, Kupffer cells and stellate cells by centrifugal elutriation. This method was particularly useful for preparing endothelial cells in high yield (100 X 10(6) cells per liver). Intravenously injected formaldehyde-treated albumin was selectively taken up by the endothelial cells. Isolated endothelial cells in suspension as well as in surface culture maintained their ability to endocytose this ligand.

Animals↗

PubMed1993

Extracellular secretion of STa heat-stable enterotoxin by Escherichia coli after fusion to a heterologous leader peptide.

The mature 19-amino acid STa heat-stable enterotoxin of E. coli has a preceding peptide of 53 amino acids which contains two domains called Pre (aa 1-19) and Pro (aa 20-53) sequences, proposed to be essential for extracellular toxin release by this host. The Pro sequence, however, has been proven not be indispensable for this process since Pro deletion mutants secrete STa. To find out if Pre and/or other unremoved natural STa flanking sequences are responsible for toxin secretion in those mutants we genetically fused mature STa directly to the leader peptide of the periplasmic E. coli heat-labile enterotoxin B-subunit (LTB). Expression of this gene fusion resulted in extracellular secretion of biologically active STa by E. coli independently of natural STa neighboring genetic sequences. Moreover, these results suggest that STa might be able to gain access to the extracellular milieu simply upon its entry into the E. coli periplasm once guided into this compartment by the LTB leader peptide. To test if extracellular secretion in this fashion might be extended to other disulfide bond-rich small peptides, the 13 amino acid conotoxin GI and a non-enterotoxic STa-related decapeptide were cloned. None of the two peptides was found in culture supernatants, in spite of high structural homology to the toxin. Failure to be secreted most likely leads to degradation as peptides were also not detected in bacterial sonicates. We hypothesize that cysteine-rich peptides must have an amino acid length and/or number of disulfide bridges closer to those in STa for them to follow this toxin secretory pathway in E. coli.

Amino Acid Sequence↗

PubMed1994

Structure of partially-activated E. coli heat-labile enterotoxin (LT) at 2.6 A resolution.

Biological toxicity of E. coli heat-labile enterotoxin and the closely related cholera toxin requires that the assembled toxin be activated by proteolytic cleavage of the A subunit and reduction of a disulfide bond internal to the A subunit. The structural role served by this reduction and cleavage is not known, however. We have crystallographically determined the structure of the E. coli heat-labile enterotoxin AB5 hexamer in which the A subunit has been cleaved by trypsin between residues 192 and 195. The toxin is thus partially activated, in that it has been cleaved but the disulfide bond has not been reduced. The structure of the A subunit in the cleaved toxin is substantially the same as that previously observed for the uncleaved AB5 structure, suggesting that although such cleavage is required for biological activity of the toxin it does not by itself cause a conformational change.

Adenosine Diphosphate Ribose↗

PubMed1984

Development of a competitive enzyme-linked immunosorbent assay (ELISA) for Escherichia coli heat-stable enterotoxin (STa).

A sensitive competitive enzyme-linked immunosorbent assay (ELISA) was developed to detect the low molecular weight heat-stable enterotoxin (STa) in culture supernatant fluids of enterotoxigenic Escherichia coli (ETEC). Competitive inhibition was observed between STa in solution and a glutaraldehyde-coupled STa-human serum albumin (HSA) conjugate bound to microtiter wells when antiserum raised against a glutaraldehyde-coupled STa-bovine serum albumin (BSA) conjugate was used as detecting antibody. No competition was observed with conjugates prepared using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide or dimethyl suberimidate and antisera raised against each conjugate. A biotin/avidin system increased the sensitivity of the assay such that 133 pg/ml of purified STa can be detected in less than 4 h. The assay was used to detect and quantify STa in culture supernatant fluids from human, porcine, and bovine ETEC isolates. No cross-reactivity was observed with the heat-labile enterotoxin (LT) or the form of ST with biological activity only in piglets (STb). Results from the quantitative STa ELISA showed good correlation (0.87) with the suckling mouse bioassay and a previously described radioimmunoassay. The quantitative assay was modified to reduce the total incubation time to less than 2 h. The qualitative STa ELISA provides a rapid and sensitive assay for clinical isolates of ETEC and should facilitate epidemiological studies on the incidence of STa-producing ETEC.

Animals↗

PubMed1986

An avidin-biotin ELISA for the detection of staphylococcal enterotoxins A and B.

The avidin-biotin system was incorporated into the enzyme-linked immunosorbent assay (ELISA) to establish a new detection method for staphylococcal enterotoxins A and B in culture supernatants. Staphylococcal protein A (SPA) does not interfere significantly with the procedure. The test shows good sensitivity for the toxins and the ease and rapidity with which the assay can be performed make it a valuable tool for the routine detection of enterotoxins.

Alkaline Phosphatase↗

PubMed1987

Mitogenic activity of staphylococcal protein A is due to contaminating staphylococcal enterotoxins.

Soluble protein A from S. aureus is widely used as a polyclonal activator of human T cells. However, recombinant protein A produced in E. coli does not show any mitogenic properties, although its IgG-binding activity is identical to protein A purified from S. aureus. Antisera against the staphylococcal enterotoxins A and B are able to specifically inhibit the response of human T lymphocytes to protein A from S. aureus. Therefore, the mitogenic principle of this extensively used T cells activator is due to minute contaminations by enterotoxins that are active in picomolar concentrations.

Cells, Cultured↗

PubMed1987

Antibody chimera technique applied to the detection of Escherichia coli heat-labile enterotoxin.

Covalently prepared chimera antibodies were tested in a ganglioside GM1 erythro-immunoassay (CERIA) for E. coli heat-labile enterotoxin (LT) detection. The antibody specific for LT was conjugated with a polyclonal antibody specific for sheep erythrocytes. The assay is based on the specific binding of LT to polystyrene-adsorbed GM1 and subsequent erythro-adsorption via chimera antibody by which the bound toxin is visualized. Enterotoxin titers determined with this CERIA method were similar to those obtained with the Vero cell assay and with ELISA. 5 ng of cholera toxin/ml may be detected with the assay. The CERIA, as described, may be used either qualitatively or quantitatively and is well suited for routine laboratory diagnosis of LT in a culture supernatant of E. coli.

Animals↗

PubMed1991

Detection of staphylococcal enterotoxin and toxic shock syndrome toxin-1 (TSST-1) by immunoblot combined with a semiautomated electrophoresis system.

An immunoblot technique combined with a semi-automated electrophoresis system has been developed for the detection of staphylococcal enterotoxins and toxic shock syndrome toxin-1 (TSST-1). The advantages of this method over other detection techniques include speed, sensitivity (10 ng/ml) and specificity. The use of semiautomated electrophoresis permits the routine detection of staphylococcal enterotoxins and TSST-1.

Bacterial Toxins↗

PubMed1987

Trace amounts of ganglioside GM1 in human milk inhibit enterotoxins from Vibrio cholerae and Escherichia coli.

Gangliosides were isolated from human milk fat and purified by silica gel column chromatography and high performance liquid chromatography (HPLC). Low amounts of the ganglioside GM1, detected by high performance thin layer chromatography (HPTLC)-immunoassay, were found in all fractions with enterotoxin-inhibitory activity, while fractions without GM1 were inactive. It is concluded that GM1 is responsible for enterotoxin-inhibitory activity in the ganglioside fraction from human milk.

Chromatography, Thin Layer↗

PubMed1983

Cytotonic enterotoxins and cytotoxic factors produced by Salmonella enteritidis and Salmonella typhimurium.

Strains of Salmonella enteritidis and Salmonella typhimurium isolated from human diarrheal cases produced heat-labile enterotoxin(s) and cytotoxic factor(s) which elongated, lysed or deformed Chinese hamster ovary cells in tissue culture. The toxin(s) caused fluid accumulation in ligated rabbit gut loops and produced increased skin permeability. Salmonella toxin produced by these strains does not cross-react immunologically with high titer Vibrio cholerae toxin antisera or heat-labile Escherichia coli enterotoxin antisera used in this study and does not bind to galactose--Sepharose gel. The activity of the toxin was not inhibited by GM1-ganglioside.

Animals↗

PubMed1990

Isolation and nucleotide sequence determination of a gene encoding a heat-stable enterotoxin of Escherichia coli.

An enterotoxin-producing strain of E. coli has been isolated from an infant patient in Shanghai Children Hospital and the gene of its heat-stable enterotoxin has been cloned and sequenced. The pre-pro-STI was composed of 72 amino acid residues corresponding to the encoding of 216 base pairs. There was only one nucleotide difference in the pro-part between this STI gene and the STIb gene reported in the literature. A guanosine base in our STI gene was substituted for a cytosine base in STIb gene resulting in a replacement of proline by alanine. Hence, the STI genes from different human sources are highly conserved though mutagenesis still occurs.

Amino Acid Sequence↗