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 271 records · Page 15Linked to original sources

PubMed1997

[Production of enterotoxins by Bacteroids fragilis strains--effect of clindamycin].

Four B. fragilis strains were examined: one nonenterotoxigenic (NTBF) and three producing enterotoxin (ETBF). The growth of cultures was determined and enterotoxin, which is released to the culture medium during growth of strains, was detected. BHI broth and BHI broth with addition of subinhibitory doses (sub-MIC) of clindamycin were applied. Bacterial cultures were incubated at 37 degrees C for 48 hours. After 4, 8, 16, 24, 48 hours of cultivation, samples of bacterial cultures were collected and the optical density was measured. Then the samples were centrifuged, supernatants were filtered through 0.45 micron filters and concentrated three times with 5000 D ultrafilters. Prepared samples were kept frozen at -70 degrees C until used. The titre of enterotoxin in samples was determined on human colon adenocarcinoma cell line HT 29/C1. Neutralization assay was performed with culture filtrates, which were enterotoxin-positive and with rabbit anti-enterotoxin serum. The results of the experiments indicate that enterotoxin is detected after 16 hours of incubation of ETBF strains. Clindamycin at subinhibitory concentrations (sub-MIC) inhibits the growth of B. fragilis cultures. The antibiotic causes also delay and decrease in enterotoxin production by ETBF strains.

Adenocarcinoma↗

PubMed1995

The enterotoxin of Clostridium perfringens type A binds to the presynaptic nerve endings in neuromuscular junctions of mouse phrenic nerve-diaphragm.

The enterotoxin of Clostridium perfringens type A, a channel-pore forming protein toxin, inhibited neuromuscular transmission in isolated mouse phrenic nerve-diaphragm preparation at low concentrations of calcium. We investigated immunohistochemically the localization of the binding sites of the enterotoxin in the preparation under the conditions in which the enterotoxin reduced maximally the amplitudes of the twitch tension elicited by electrical stimulations to the phrenic nerve. Under the conditions, double immunohistochemical staining of the preparation with (1) rabbit anti-enterotoxin IgG-rhodamine-labeled goat anti-rabbit IgG and (2) mouse anti-synaptophysin (one of the synaptic vesicle-specific membrane proteins)-fluorescein isothiocyanate (FITC)-labeled goat anti-mouse IgG showed that the enterotoxin binds specifically to most of the sites which were stained with anti-synaptophysin exactly in the same configurations having the shapes of the nerve endings in the endplates. The thin section electron micrographs of the enterotoxin-intoxicated preparation showed no alterations in the ultrastructure of the neuromuscular junction and the nerve endings filled with numerous synaptic vesicles. The present results, together with our previous electrophysiological findings, indicate that the enterotoxin binds specifically to the presynaptic nerve endings and inhibits neurotransmitter release at the neuromuscular junction.

Animals↗

PubMed1998

Detection of Bacteroides fragilis enterotoxin gene by PCR.

Bacteroides fragilis constitutes about 1% of the bacterial flora in intestines of normal humans. Enterotoxigenic strains of B. fragilis have been associated with diarrheal diseases in humans and animals. The enterotoxin produced by these isolates induces fluid changes in ligated intestinal loops and an in vitro cytotoxic response in HT-29 cells. We developed a nested PCR to detect the enterotoxin gene of B. fragilis in stool specimens. After DNA extraction, a 367-bp fragment was amplified with two outer primers. The amplicon from this reaction was subjected to a second round of amplification with a set of internal primers. With these inner primers, a 290-bp DNA fragment was obtained which was confirmed as part of the B. fragilis enterotoxin gene by Southern blotting with a nonradioactive internal probe and a chemiluminescence system. By this approach, B. fragilis enterotoxin gene sequences were detected in eight known enterotoxigenic human isolates and nine enterotoxigenic horse isolates. No amplification products were obtained from DNA extracted from 28 nonenterotoxigenic B. fragilis isolates or B. distasonis, B. thetaiotaomicron, B. uniformis, B. ovatus, Escherichia coli, or Clostridium difficile. The sensitivity of this assay allowed us to detect as little as 1 pg of enterotoxin DNA sequences or 100 to 1,000 cells of enterotoxigenic B. fragilis/g of stool. Enterotoxin production of all isolates was confirmed in vitro in HT-29 cells. A 100% correlation was obtained between enterotoxin detection by cytotoxin assay and the nested PCR assay. This rapid and sensitive assay can be used to identify enterotoxigenic B. fragilis and may be used clinically to determine the role of B. fragilis in diarrheal diseases.

Animals↗

PubMed1992

Escherichia coli enterotoxin (STa) binds to receptors, stimulates guanyl cyclase, and impairs absorption in rat colon.

To determine the contribution of the colon in Escherichia coli heat-stable enterotoxin-mediated diarrheal disease, toxin binding, guanyl cyclase activation, and toxin-induced water flux in the rat colon and ileum were compared. Scatchard analysis suggested a single class of heat-stable enterotoxin receptors with an affinity constant of binding of 10(9) L/mol in both colonocytes and ileocytes; however, the number of toxin receptors per cell was 3.5-fold greater in coloncytes than ileocytes (8.32 +/- 1.33 x 10(5) vs. 2.33 +/- 0.28 x 10(5) receptors per cell; P = 0.02). Heat-stable enterotoxin stimulated guanyl cyclase activation in an identical dose-dependent manner in proximal colonic and ileal membranes, with similar sensitivity and maximum response. Heat-stable enterotoxin also inhibited net water flux to a similar degree in both colon and ileum (-47.8 vs. -48.4 microL.cm-1.h-1, respectively) at a dose of 8 nmol/L. At this dose in the colon, because of a higher baseline of absorption, absorption continued, but at a diminished level. At this dose in the ileum, heat-stable enterotoxin induced net secretion. These data are consistent with the concept that heat-stable enterotoxin-induced diarrheal disease results from a decreased absorptive capacity in the colon in the face of increased small intestinal fluid secretion.

Analysis of Variance↗

PubMed1996

Crystal structure of a new heat-labile enterotoxin, LT-IIb.

BACKGROUND: Cholera toxin from Vibrio cholerae and the type I heat-labile enterotoxins (LT-Is) from Escherichia coli are oligomeric proteins with AB5 structures. The type II heat-labile enterotoxins (LT-IIs) from E. coli are structurally similar to, but antigenically distinct from, the type I enterotoxins. The A subunits of type I and type II enterotoxins are homologous and activate adenylate cyclase by ADP-ribosylation of a G protein subunit, G8 alpha. However, the B subunits of type I and type II enterotoxins differ dramatically in amino acid sequence and ganglioside-binding specificity. The structure of LT-IIb was determined both as a prototype for other LT-IIs and to provide additional insights into structure/function relationships among members of the heat-labile enterotoxin family and the superfamily of ADP-ribosylating protein toxins. RESULTS: The 2.25 A crystal structure of the LT-IIb holotoxin has been determined. The structure reveals striking similarities with LT-I in both the catalytic A subunit and the ganglioside-binding B subunits. The latter form a pentamer which has a central pore with a diameter of 10-18 A. Despite their similarities, the relative orientation between the A polypeptide and the B pentamer differs by 24 degrees in LT-I and LT-IIb. A common hydrophobic ring was observed at the A-B5 interface which may be important in the cholera toxin family for assembly of the AB5 heterohexamer. A cluster of arginine residues at the surface of the A subunit of LT-I and cholera toxin, possibly involved in assembly, is also present in LT-IIb. The ganglioside receptor binding sites are localized, as suggested by mutagenesis, and are in a position roughly similar to the sites where LT-I binds its receptor. CONCLUSIONS: The structure of LT-IIb provides insight into the sequence diversity and structural similarity of the AB5 toxin family. New knowledge has been gained regarding the assembly of AB5 toxins and their active-site architecture.

Amino Acid Sequence↗

PubMed1988

Receptors and cGMP signalling mechanism for E. coli enterotoxin in opossum kidney.

Receptors for the heat-stable enterotoxin produced by Escherichia coli were found in the kidney and intestine of the North American opossum and in cultured renal cell lines. The enterotoxin markedly increased guanosine 3',5'-cyclic monophosphate (cGMP) production in slices of kidney cortex and medulla, in suspensions of intestinal mucosa, and in the opossum kidney (OK) and rat kangaroo kidney (PtK-2) cell lines. In contrast, atrial natriuretic factor elicited much smaller increases in cGMP levels of kidney, intestine, or cultured kidney cell lines. The enterotoxin receptors in OK cells had a molecular mass of approximately 120 kDa when measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of receptors crosslinked with 125I-enterotoxin. The occurrence of receptors for the E. coli peptide in OK implies that these receptors may be involved in the regulation of renal tubular function in the opossum. E. coli enterotoxin caused a much larger increase in urine cGMP excretion (10- to 50-fold over control) than did atrial natriuretic factor when these peptides were injected intravenously into opossums. However, atrial natriuretic factor elicited a marked diuresis, natriuresis, and increased urinary excretion of calcium, phosphate, potassium, and magnesium. In contrast, the enterotoxin did not acutely influence OK fluid and electrolyte excretion. Thus the substantial increase in cGMP synthesis produced by the bacterial peptide in OK cortex and medulla in vitro and the increased renal excretion of cGMP in vivo were not associated with changes in electrolyte or water excretion. Whether cGMP represents a second messenger molecule in the kidney is an interesting question that was raised but not answered in this series of experiments.

Animals↗

PubMed1979

The effects of Clostridium perfringens enterotoxin on morphology, viability, and macromolecular synthesis in Vero cells.

Vero (African green monkey kidney) cells grown in tissue culture monolayer were sensitive to Clostridium perfringens enterotoxin. Within 30 minutes of exposure to the enterotoxin gross morphological damage was observed and within 40 minutes approximately 75% of the cells had detached. Nearly half of the cells were nonviable following 35 to 40 minutes incubation with the enterotoxin. Doses as low as 0.1 ng caused small but detectable inhibition of plating efficiency of the cells while more than 100 ng caused the inhibition to approach 100%. Total inhibition of DNA, RNA, and protein synthesis occurred within 30 minutes exposure to enterotoxin. Heat inactivated enterotoxin had no apparent effects upon cellular morphology, detachment, viability, plating efficiency, or incorporation. We propose that the enterotoxin induces structural damage to the cytoplasmic membrane which results in loss of electrolytes and other essential substances from the cells. The outcome of this process is shut down of macromolecular synthesis, gross morphological damage, and eventual death of the cell.

Animals↗

PubMed1989

Specificity, cross-reactivity and competition profile of monoclonal antibodies to staphylococcal enterotoxins B and C1 detected by indirect enzyme-linked immunosorbent assays.

A group of monoclonal antibodies to the staphylococcal enterotoxins B and C1 without any cross-reactivity to the other known staphylococcal enterotoxins A, C2, C3, D and E was developed. The monoclonal antibodies were compared in competition ELISA's with regard to affinity and epitope recognition. Three different groups could be classified: Group 1, consisting of the MAbs B/3-4 and B/3-8, recognizes in identical manner staphylococcal enterotoxin B. Also group 2 (MAb B/3-5) recognizes only staphylococcal enterotoxin B, yet group 1 and 2 do not compete with each other in the competition ELISA and therefore own different paratopes. Group 3 (MAb C1/2-3 and C1/4-6) reacts exclusively with staphylococcal enterotoxin C1, not even with staphylococcal enterotoxins C2 and C3.

Antibodies, Monoclonal↗

PubMed1985

Morphological alterations and changes in cellular cations induced by Clostridium perfringens type A enterotoxin in tissue culture cells.

The morphological alterations (bleb-balloon formation) induced by Clostridium perfringens type A enterotoxin in HeLa and Vero cells were studied under defined extracellular conditions. The action of enterotoxin was found to depend on the temperature but not on energy metabolism. The morphological alterations by the enterotoxin occurred in phosphate buffered saline containing Ca2+ and Mg2+. Of the constituents of the buffered saline, Ca2+ was essential for the morphological alterations and other ions were interchangeable. The morphological alterations by the enterotoxin occurred also in 10 mM Hepes-Na buffer, pH 7.2 containing NaCl, KCl or choline chloride at a concentration of over ca. 50 mM and in 10 mM Hepes-Ca buffer, pH 7.2 containing CaCl2 at a concentration of over ca. 50 mM. Addition of sucrose to the medium prevented induction of the morphological alterations. The amount of sucrose necessary to protect the cells increased with increase in NaCl, KCl or CaCl2 concentration in the medium. A calcium ionophore A23187 mimicked the action of enterotoxin. Examination of the cation contents of the cells by atomic absorption spectrophotometry showed early and rapid increase of Ca2+ during intoxication with concomitant changes in Na+, K+ and Mg2+ that reduced the ion concentration gradients between inside and outside of the cell present before toxin treatment. The mechanism of action of C. perfringens type A enterotoxin is discussed on the basis of these findings.

Animals↗

PubMed1992

Effect of six organic acids on staphylococcal growth and enterotoxin production.

Four Staphylococcus aureus strains were incubated at 37 degrees C for 24 h in broth progressively acidified with lactic, citric, ascorbic, acetic, pyruvic and propionic acids, and their survival rate and enterotoxin producing ability was studied. Acids were chosen based on their frequent use by the food industry. Periodically, samples were withdrawn to determine counts, pH and the presence of enterotoxins A, B, C, and D. For a given acid, the effect on growth and enterotoxin synthesis was different. The most inhibitory acid for the growth of strains FRI-100 and FRI-472 was pyruvic acid, for strain FRI-137 was lactic acid, all six acids were equally effective on strain S6. Lactic acid was very inhibitory to enterotoxin synthesis, but the effect on this parameter of acetic and citric acids was almost nil. Enterotoxins were seen to be inactivated at acid pH values; enterotoxin B was the most resistant to inactivation.

Acetates↗

PubMed2007

A quantitative real-time immuno-PCR approach for detection of staphylococcal enterotoxins.

Bacterial intoxications represent a substantial public health concern with enterotoxins produced by Staphylococcus aureus among the most common causes of food poisoning. In addition to their role in the pathogenicity of food poisoning, staphylococcal enterotoxins have profound effects on the immune system as members of the family of pyrogenic toxin superantigens. As the classical diagnostic bioassays as well as the routinely used immunological methods are hampered by several drawbacks regarding sensitivity, specificity, and practicability, there is a need for the timely identification of toxins by highly sensitive and specific methods. To combine the versatility of an enzyme immunoassay (EIA) with the amplification power of the PCR, a quantitative real-time immuno-PCR (qRT-iPCR) was developed for the detection of staphylococcal enterotoxins A and B and compared to a commercially available EIA. A broadly applicable tool for signal amplification of pre-formed immunocomplexes was established by covalent binding of a reporter DNA to secondary detection antibodies. Therefore, the amino-modified reporter DNA was coupled successfully to N-succinimidyl-S-actyl-thioacetate-activated secondary detection antibodies. The qRT-iPCR was able to detect highly reproducibly as low as approximately 0.6 to 6 pg (4 to 40 amol/microl) of staphylococcal enterotoxin B and staphylococcal enterotoxin A, respectively. In conclusion, the qRT-iPCR approach was shown to overcome clearly the sensitivity limit of traditional immunological detection procedures for bacterial toxins, as demonstrated in this study for staphylococcal enterotoxins. The development of a stable antibody-DNA conjugate providing a universal signal amplification offers a versatile as well as a highly sensitive and specific tool for diagnostic and research purposes generally applicable for pre-formed antibody-antigen complexes.

Antibodies, Viral↗

PubMed2002

Detection of enterotoxin genes in mosquito-larvicidal Bacillus species.

The presence of the B component of hemolysin BL (hblA), enterotoxin BceT (bceT), and enterotoxin S (entS) genes in mosquito-larvicidal Bacillus sp., including 25 B. sphaericus and 4 B. thuringiensis subsp. israelensis strains, has been analyzed by multiplex PCR in this study. The results showed that all four B. thuringiensis strains contain the hblA gene and the sequences of bceT and entS genes. However, none of the enterotoxin gene sequences were detected in the B. sphaericus strains. The enterotoxin production in all strains has also been analyzed by using two commercial immunoassay kits (TECRA and RPLA), and it has been proved that all the B. thuringiensis strains and one B. cereus strain can produce enterotoxins during growth. No enterotoxin activity could be detected in B. sphaericus strains.

Animals↗

PubMed2006

The production of Bacillus cereus enterotoxins is influenced by carbohydrate and growth rate.

Enterotoxin production is a key factor in Bacillus cereus food poisoning. Herein, the effect of the growth rate (mu) on B. cereus toxin production when grown on sucrose was studied and the Hemolytic BL enterotoxin (HBL) and nonhemolytic enterotoxin (Nhe) production by B. cereus was compared according to carbohydrate at mu = 0.2 h(-1). The anaerobic growth was carried out on continuous cultures in synthetic medium supplemented with glucose, fructose, sucrose, or an equimolar mixture of glucose and fructose. Concerning the HBL and Nhe enterotoxin production: (1) the highest enterotoxin production has occurred at mu = 0.2 h(-1) when growing on sucrose; (2) HBL production was repressed when glucose was consumed and the presence of fructose (alone or in mixture) cancelled glucose catabolite repression; (3) the consumption of sucrose increased Nhe production, which was not affected by the catabolite repression. Furthermore, analysis of the fermentative metabolism showed that whatever the mu or the carbon source, B. cereus used the mixed acid fermentation to ferment the different carbohydrates. The enterotoxin productions by this strain at mu = 0.2 h(-1) are highly influenced by the carbohydrates that do not involve any fermentative metabolism changes.

Bacillus cereus↗

PubMed1988

Effect of growth of a commercial starter culture on growth of Staphylococcus aureus and thermonuclease and enterotoxins (C1 and C2) production in broth cultures.

Staphylococcus aureus strains FRI 137 (enterotoxin C1 producer) and FRI 361 and L 2 (enterotoxin C2 producers) were grown alone and in the presence of a mixed commercial starter culture (Streptococcus lactis, Streptococcus cremoris and Streptococcus lactis subsp. diacetylactis). Lactic acid bacteria had a slight inhibitory effect on S. aureus population and only during the late stages of growth. In contrast, enterotoxin synthesis was strongly inhibited, inhibition at 18 h being 89% (FRI 137), 80% (FRI 361) and 69% (L 2). Enterotoxin C1 was produced and accumulated during all phases of growth in pure and mixed culture, but associative growth resulted in reduction of enterotoxin C2 after 24-36 h. In mixed culture, high producers of thermonuclease (FRI 137 and L 2) showed an early decrease in enzyme activity followed by an increase, but it never reached levels attained in pure culture. Thermonuclease was detected whenever enterotoxin was detected, but production curves did not parallel each other.

Bacteriological Techniques↗

PubMed1988

Evaluation of enzyme-linked immunosorbent assay (ELISA) for detection of staphylococcal enterotoxin in foods.

Two ELISA kits were employed to detect staphylococcal enterotoxin A, B, C and D in foods to which enterotoxin had been added or which had been artificially contaminated with enterotoxin-producing strains of Staphylococcus aureus. The sensitivity was satisfactory, and enterotoxins were detected by both ELISA kits in all positive samples. Weak positive reactions with one ELISA kit caused some difficulties in evaluation of samples. Enterotoxins A, B and C detected in small amounts (2-22 ng/ml) in minced fried beef were not detectable after heating at 80 degrees C, whereas enterotoxin D detected in considerably greater amounts (783 ng/ml) was reduced to 0.4% of this amount.

Enterotoxins↗

PubMed1990

The effects of irradiation and temperature on the immunological activity of staphylococcal enterotoxin A.

The effects of irradiation and temperature on purified staphylococcal enterotoxin A were investigated using sensitive ELISA systems. Thermal inactivation of staphylococcal enterotoxin A in phosphate-buffered saline was considerably faster at temperatures of 60, 70, 115 and 121 degrees C than at 90 and 100 degrees C. In gelatin phosphate buffer, staphylococcal enterotoxin A was completely inactivated by irradiation at 8.0 kGy; in a 15% mince slurry, however, 27-37% of staphylococcal enterotoxin A remained at this level of irradiation. Even at a dose of 23.7 kGy, 16-26% residual staphylococcal enterotoxin A could still be detected. Generally, increasing the mince concentration increased the protection against the effect of irradiation on staphylococcal enterotoxin A. However, the protective effect of mince at a concentration of 50% was less than at a mince concentration of 30%. Both irradiation and heat processing of food should only be used in conjunction with good manufacturing practices to prevent proliferation of microorganisms and toxin productions.

Animals↗

PubMed1992

Influence of aw value and storage temperature on the multiplication and enterotoxin formation of staphylococci in dry-cured raw hams.

Growth and enterotoxin A production in dry-cured raw ham, with different aw and pH values, was investigated for Staphylococcus aureus strain FRJ-100 over a temperature range of 20-35 degrees C when stored for up to 7 days. Enterotoxin production took place at all temperatures tested in the meat of ham that was cured, but not dried (aw 0.95). In dry-cured raw ham with an aw-value of about 0.92, and stored at 20 degrees C, no enterotoxin production was detectable within the 7-day storage period, whereas enterotoxin was produced at the higher temperatures. In ham with an aw of about 0.89, enterotoxin was produced only when stored for 7 days at 35 degrees C. Critical points for S. aureus multiplication and enterotoxin-formation during production and storage of dry-cured raw ham are discussed.

Animals↗

PubMed1992

Detection of Clostridium perfringens enterotoxin gene by the polymerase chain reaction amplification procedure.

The polymerase chain reaction (PCR) procedure was evaluated to see if it is a simple and rapid method to detect Clostridium perfringens enterotoxin gene. The method, involving the use of two synthesised primers and gene amplification by the PCR procedure, detects a DNA fragment of 364 base pairs of C. perfringens enterotoxin gene by gel electrophoresis. The enterotoxin gene of strains was detected by use of purified chromosomal DNA. The supernatant of sporulating cultures in a sporulating medium was able to be used as template DNA. Template DNA can be obtained by merely culturing the strain in DS medium, a sporulating medium, for 48 h at 37 degrees C. All C. perfringens strains showing positive results in the PCR procedure were demonstrated to produce enterotoxin by a conventional method and all strains showing negative results were enterotoxin negative. To detect the enterotoxin gene in stool specimens by the PCR procedure, the specimen was heat-treated for 10 min at 90 degrees C and cultured in a sporulating medium, the supernatant of which was used as template DNA. From the stool specimens showing positive results in the PCR procedure by this method, enterotoxigenic C. perfringens was isolated from the heat-treated specimens. Thus, it is possible to detect enterotoxigenic C. perfringens in stools without isolation of the organism.

Base Sequence↗