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PubMed1992

Enterotoxin production in different Staphylococcus aureus biotypes isolated from food and meat plants.

Strains of Staphylococcus aureus isolated in Belgium and Zaïre from food and from various sources in the meat industry were biotyped, phage typed and tested for staphylococcal enterotoxin (SE) production. Thirty of the 185 strains examined produced one or more SE, and 23 of these belonged to the human biotype. Most SE-positive strains belonged to phage groups III and Mixed, or were not typable. None of the poultry-like biotype strains, which were frequent in nasal carriers among workers in meat plants as well as in minced meat, produced enterotoxins. Avian biotype strains similarly were negative.

Abattoirs↗
PubMed1994

A comparison of ELISA and RPLA for detection of Bacillus cereus diarrhoeal enterotoxin.

Fourteen strains of Bacillus cereus isolated from different sources were examined for their ability to produce diarrhoeal enterotoxin by two commercial immunoassay kits (Oxoid BCET-RPLA and Tecra ELISA) and the microslide immunodiffusion assay. One strain that was positive in monkey feedings, as well as a number of other strains isolated from diarrhoeal outbreaks, gave positive results in the ELISA and negative results in the RPLA test systems. When tested in the microslide assay, these strains produced only one antigen which formed a line of identity with the reference toxin. The results of the control toxins provided with the kits substantiated that the two commercial assays did not detect the same antigen. Cultures positive with both assay kits were shown to produce diarrhoeal enterotoxin (by a line of identity) and other antigens in the microslide immunodiffusion assay.

Antigens, Bacterial↗
PubMed2005

Diversity of Staphylococcus aureus enterotoxin types within single samples of raw milk and raw milk products.

AIM: To find out if testing of up to 10 Staphylococcus aureus isolates from each sample from raw milk and raw milk products for staphylococcal enterotoxin (SE) might increase the chances of identifying potential sources of food intoxication. METHODS AND RESULTS: Altogether 386 S. aureus isolates were tested for the presence of SE by reversed passive latex agglutination (SET-RPLA), and SE genes (se) by a multiplex polymerase chain reaction (PCR). In 18 of 34 (53%) S. aureus positive samples a mixture of SE and/or se positive and negative isolates were identified. Multiplex PCR increased the number of potential SE producing strains, i.e. isolates that harboured se, with 51% among the product and 48% among the raw bovine milk isolates. Examination by pulsed-field gel electrophoresis mostly confirmed clonal similarity among isolates sharing SE/se profile, but did not further differentiate between them. CONCLUSIONS: Isolates of S. aureus collected from one sample may show great diversity in SE production and different plating media seem to suppress or favour different strains of S. aureus. SIGNIFICANCE AND IMPACT OF THE STUDY: Several isolates of S. aureus from each sample should be tested for enterotoxin production in cases with typical SE intoxication symptoms with methods that are able to reveal new SE/se.

Animals↗
PubMed1985

Effect of lidamidine-HCl on Escherichia coli heat-stable enterotoxin-induced jejunal water and electrolyte secretion in neonatal piglets.

Neonatal piglets were anesthetized, and two jejunal loops, 20 cm in length, were prepared. Then, either water or 0.12, 0.25, 0.5 or 1.0 mg/kg of lidamidine-HCl was injected intraduodenally on a randomized basis, one treatment per pig. Following this, a crude heat-stable enterotoxin (ST) preparation produced from E. coli no. 1261 was injected into the proximal jejunal loop, and trypticase soy broth (TSB) (with osmolality adjusted to equal the enterotoxin preparation) was injected into the distal jejunal loop. Piglets remained anesthetized for 3 h and were then killed. Fluid was collected from the loops for measurement of volume and Na, K and Cl concentration. Empty loop lengths were measured. There was a significant dose-related reduction of volume and Cl content, and a dose-related, but not significant, reduction in Na content in St-treated loops. A comparison of the mean differences in responses between toxin- and TSB-treated loops indicated that the major 'counter-toxic' effect of the lidamidine was a dose-related increase in water and electrolyte absorption.

Animals↗
PubMed2005

Association of beta2 toxin production with Clostridium perfringens type A human gastrointestinal disease isolates carrying a plasmid enterotoxin gene.

Clostridium perfringens type A isolates carrying an enterotoxin (cpe) gene are an important cause of human gastrointestinal diseases, including food poisoning, antibiotic-associated diarrhoea (AAD) and sporadic diarrhoea (SD). Using polymerase chain reaction (PCR), the current study determined that the cpb2 gene encoding the recently discovered beta2 toxin is present in <15% of food poisoning isolates, which typically carry a chromosomal cpe gene. However, >75% of AAD/SD isolates, which usually carry a plasmid cpe gene, tested cpb2(+) by PCR. Western blot analysis demonstrated that >97% of those cpb2(+)/cpe(+) AAD/SD isolates can produce CPB2. Additional PCR analyses, sequencing studies and pulsed field gel electrophoresis experiments determined that AAD/SD isolates carry cpb2 and cpe on the same plasmid when IS1151 sequences are present downstream of cpe, but cpb2 and cpe are located on different plasmids in AAD/SD isolates where IS1470-like sequences are present downstream of cpe. Those analyses also demonstrated that two different CPB2 variants (named CPB2h1 or CPB2h2) can be produced by AAD/SD isolates, dependent on whether IS1470-like or IS1151 sequences are present downstream of their cpe gene. CPB2h1 is approximately 10-fold more cytotoxic for CaCo-2 cells than is CPB2h2. Collectively, these results suggest that CPB2 could be an accessory toxin in C. perfringens enterotoxin (CPE)-associated AAD/SD.

Amino Acid Sequence↗
PubMed1993

Staphylococcal enterotoxin B promotes deletion and functional inactivation of CD4V beta 8-positive cells in the absence of CD8 T cells.

The staphylococcal enterotoxins stimulate discrete subsets of T cells depending on their expression of particular V genes. Among these, staphylococcal enterotoxin B (SEB) vigorously stimulates V beta 8+ cells. This stimulation results in proliferation of both CD4+V beta 8+ and CD8+ T cells and eventually to anergy and clonal deletion in the former subset. We have examined the possible role of CD8+ T cells in the response of CD4+ cells to SEB, by in vivo CD8+ T-cell-depletion. We found no qualitative difference in the responses of untreated and CD8+ T-cell depleted mice to SEB; however, a small quantitative difference in deletion was observed. Thus it appears that on the whole the response of CD4+V beta 8+ T cells to SEB is independent of CD8+ T-cell effector function, although the latter may play a partial role.

Animals↗
PubMed1982

Amino-acid sequence of a heat-stable enterotoxin produced by human enterotoxigenic Escherichia coli.

A heat-stable enterotoxin produced by a human strain of enterotoxigenic Escherichia coli was extensively purified by reverse-phase high-performance liquid chromatography. The minimum effective dose of the purified toxin to cause fluid accumulation in suckling mice was 2.5 ng. The amino acid sequence of the purified toxin was determined by Edman degradation and a combination of fast atom bombardment mass spectrometry and carboxypeptidase digestion to be Asn-Ser-Ser-Asn-Tyr-Cys-Cys-Glu-Leu-Cys-Cys-Asn-Pro-Ala-Cys-Thr-Gly-Cys-Tyr. This sequence was identical to that deduced from the nucleotide sequence encoding a human heat-stable enterotoxin, reported by Moseley et al., except for the C-terminal Tyr residue.

Amino Acid Sequence↗
PubMed1991

Protein A insensitive ELISA detection of staphylococcal enterotoxin B.

A sandwich enzyme-linked immunosorbent assay to detect staphylococcal enterotoxin B was developed using rat monoclonal antibodies as capture antibodies and as a biotinylated conjugate. This test was sensitive, less than 1 ng/ml of enterotoxin B was detected and interference by protein A was prevented by the use of rat monoclonal antibodies of the IgG2a isotype which were insensitive to protein A even at concentrations greater than 1000 ng/ml.

Animals↗
PubMed1995

Salmonella enterotoxin (stn) gene is prevalent among strains of Salmonella enterica, but not among Salmonella bongori and other Enterobacteriaceae.

All strains and serovars of Salmonella enterica such as serovar Typhimurium, Enteritidis, Dublin, Typhi, etc. were found to carry the Salmonella enterotoxin determinant stn as far as examined in PCR and hybridization studies. However, using MDCK cells for testing the toxicity of the strains under investigation, only a limited number of stn positive strains revealed phenotypically the Salmonella enterotoxin Stn. In contrast to S. enterica, other Enterobacteriaceae including Salmonella bongori were found neither genotypically nor phenotypically Stn toxin positive.

Base Sequence↗
PubMed1997

Rapid and differential detection of two analogous enterotoxins of Vibrio cholerae and enterotoxigenic Escherichia coli by a modified enzyme-linked immunosorbent assay.

The principle of a novel ELISA (nylon-slip immuno-test, NSIT) was applied to the differential detection of two analogous enterotoxins, cholera toxin (CT) of Vibrio cholerae and heat-labile enterotoxin (LT) of enterotoxigenic Escherichia coli. The results obtained for CT and LT detection by a single test were sufficiently sensitive (87.9 and 100%) and specific (100 and 94.7%) in the differential detection test, when compared with the result of a colony hybridization test with DNA probes. The results suggest that the novel ELISA is applicable to the diagnosis of bacterial infections, by means of differential immunological detection of toxins in a single test.

Bacterial Toxins↗
PubMed1993

Location of the enterotoxin gene from Salmonella typhimurium and characterization of the gene products.

The enterotoxin gene (stn) in Salmonella typhimurium (Q1 strain) was confined to an 800 bp ClaI-EcoRI genomic DNA fragment (pCE3) that coded for two polypeptides (25 and 12 kDa) under the control of the T7 RNA polymerase/promoter system. The appearance of the 25 kDa protein corresponded to the enterotoxic activity, as determined by elongation of Chinese hamster ovary (CHO) cells, fluid accumulation in rabbit intestinal loops, and altered vascular permeability in rabbit skin. The stn gene products (STN) caused an elevation of intracellular cAMP in CHO cells. These values were at control levels in stn mutants devoid of enterotoxicity, and the 25-kDa protein concurrently disappeared. The biological activity of the heat-labile enterotoxin was blocked by GM1 ganglioside and neutralized by affinity-purified antibodies made against cholera toxin. The 12 kDa protein however was not correlated with an enterotoxic response.

Animals↗
PubMed1994

Salmonella typhimurium enterotoxin epitopes shared among bacteria.

The deduced amino acid sequence of the cloned Salmonella enterotoxin gene (stn) was used to prepare anti-peptide antibodies. These antibodies were then employed to screen isolates of this enteric pathogen for the synthesis of protein enterotoxin (Stn). Cell lysates of all Salmonella isolates tested displayed a prominent immunoblot band of approximately 29 kDa, which was consistent with the size of the cloned stn gene product. Among other Gram-negative bacteria examined, isolates of Klebsiella, Enterobacter, and Citrobacter exhibited a similar-sized protein that reacted strongly with the Stn antibodies. Since the stn gene was located opposite the hydrogenase regulatory genes (hydHG) required for hydrogen metabolism in bacteria, our data suggested that only in Salmonella and some other members of the family Enterobacteriaceae had the DNA sequence evolved, presumably through point mutations, into an expressed gene product of similar size.

Antibodies, Bacterial↗
PubMed1996

Characterisation of a non-haemolytic enterotoxin complex from Bacillus cereus isolated after a foodborne outbreak.

Three enterotoxic components have been isolated from a strain of Bacillus cereus which was involved in a large food poisoning outbreak in Norway in 1995. The components were purified by chromatography on three different columns. Three proteins of 39, 45 and 105 kDa, respectively, were found to be necessary for maximum cytotoxicity. The amino acid N-terminal sequences of the 39 and 45 kDa proteins were determined. The 45 kDa component was the same protein as the main antigen detected in the Bacillus Diarrhoeal Enterotoxin Visual Immunoassay (Tecra). The 39 kDa protein showed some similarity to the L1 protein of haemolysin BL from B. cereus. Furthermore, the three toxic components were all recognised by a polyclonal antiserum reported to detect enterotoxin from B. cereus. The proteins were different from the B- and L2-components of haemolysin BL, previously suggested to be a primary virulence factor, and had no detectable haemolytic activity.

Amino Acid Sequence↗
PubMed1997

Histidine-44 of the A subunit of Escherichia coli enterotoxin is involved in its enzymatic and biological activities.

We examined the role in toxicity of histidine-44 of the A subunit of Escherichia coli enterotoxin, which is located in the active site cavity close to glutamic acid-112. Although amino acid substitution of histidine-44 usually renders a mutant toxin unstable to trypsin, one mutant, alanine-44 (His44Ala) was found to be stable. His44Ala did not show any agmatine:ADP-ribosyltransferase activity in the presence or absence of recombinant ADP-ribosylation factor. It showed no diarrheal or rabbit skin permeability activity and was a competitor in enterotoxin-ADP-ribosyltransferase assays containing recombinant ADP-ribosylation factor. These results suggest that like glutamic acid-112, histidine-44 plays an essential role in toxicity. A tentative model, which explains NAD+ catalysis and the transfer of the ADP-ribosyl moiety to a target amino acid, is proposed for histidine-44 and glutamic acid-112.

ADP-Ribosylation Factors↗
PubMed1993

Immunoregulatory effects of superantigens: interactions of staphylococcal enterotoxins with host MHC and non-MHC products.

Staphylococcus aureus carries a highly conserved set of genes which encode a set of secreted enterotoxins. Although it is likely that these enterotoxins affect the host/parasite in favor of the bacterium, we do not understand the molecular basis of this interaction. We summarize recent evidence that defines two types of interaction between the bacterial toxin and host cellular receptors that may subvert the host immune response to S. aureus. An interaction between the toxin and class II products on APC can result in inhibition of costimulatory activity and thus impair clonal expansion of T cells specific for bacterial antigens. Studies using anti-class II antibodies suggest that this may reflect transmission of a negative signal to APC after ligation of class II products. A second interaction between a subset of toxins, including SEC, with non-MHC products stimulates both T-cell proliferation as well as toxin-specific cytotoxic T cells (CTL). We put forward the hypothesis that this interaction reflects binding of a VCAM-1-like subsequence of SEC to VLA-4 expressed by activated target cells. We suggest that this interaction may serve to inhibit the host response by subversion of lymphocyte homing to sites of infection by SEC-producing staphylococci and by local elimination of (VLA-4+) memory T cells.

Amino Acid Sequence↗
PubMed1981

Separation and characterization of enterotoxin and two haemolysins from Aeromonas hydrophila.

Aeromonas hydrophila produces two haemolysins, now designated alpha- and beta-haemolysin (formerly aerolysin or cytotoxic protein), and one enterotoxin. These toxins were separated and purified by isoelectric focusing and gel chromatography. Alpha- and beta-haemolysin differ with regard to prerequisites for their elaboration, such as selection of A. hydrophila strains and temperature and time for cultivation. The nature of their lytic effects on erythrocytes and toxic effects on tissue culture cells differs significantly. Alpha- but not beta-haemolysin was inactivated by reducing agents and activated by oxygen, while beta-haemolysin was more resistant than alpha-haemolysin to proteolytic enzymes but was inactivated by crude gangliosides. When separated from the two haemolysins, the enterotoxin gave positive reactions in the rabbit intestinal loop test, the rabbit skin and the adrenal Y1 cell test, though the sensitivity of the Y1 cell was low as compared with cholera toxin and E. coli LT toxin. No cytotoxic effects were obtained in HeLa cells.

Aeromonas↗
PubMed1992

Enterotoxin and toxic shock syndrome toxin-one production by staphylococci isolated from mastitis in sheep.

From 160 staphylococci isolated from ovine mastitis, 125 were identified as coagulase-positive staphylococci (CPS) and 35 as coagulase-negative staphylococci (CNS). Of these, 108 (87.8%) S. aureus produced at least one of the staphylococcal enterotoxins (SE) described. However, no CNS was found to be enterotoxigenic. Enterotoxin C (SEC) was the type most frequently produced. TSST-1 was shown to be produced by 91 (74.0%) of S. aureus, almost invariably in combination with SEC. Three CNS strains were also found to produce TSST-1 (two strains of S. xylosus and one strain of S. epidermidis).

Animals↗