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PubMed1975

Heterogeneity of enterotoxin-like protein extracted from spores fo Clostridium perfringens type A.

Enterotoxin-like protein was extracted from spores of three enterotoxin-positive and three enterotoxin-negative strains of Clostridium perfringens type A by urea/mercaptoethanol, alkaline mercaptoethanol and alkaline dithiothreitol. Disc immunoelectrophoresis demonstrated that three distinct enterotoxin-like proteins could be extracted. In 7% acrylamide gels, type I, type II, and type III enterotoxinlike proteins had relative mobilities of 0.52, 0.63, and 0.73 respectively. In contrast to disc immunoelectrophoresis, immunoelectrophoresis in agar gel demonstrated identical electrophoretic properties for the various entertoxin-like proteins. Immunoelectrofocusing experiments gave isoelectric points of 4.43, 4.43, 4.36, and 4.52 for purified entertoxin and type I, type II, and type III enterotoxin-like proteins respectively. Ferguson plots (i.e., log relative mobility versus acrylamide concentration) yielded nonparallel lines which intersected at a nonsieving concentration of acrylamide indicating that the various species of enterotoxin-like protein differed in size. Estimation of the molecular weight of purified enterotoxin and the three species of enterotoxin-like protein was done by comparing the slopes obtained in Ferguson plots with those obtained using proteins of a known molecular weight. Molecular weights of 38000, 36500, 23000, and 15400 were obtained for purified enterotoxin, type I, type II, and type III enterotoxin-like protein respectively. Collectively, the evidence indicates that fractionation of the different species of enterotoxin-like protein was due primarily to differences in their size, and that different forms of enterotoxin-like protein can be extracted from spores of different strains of C. perfringens type A.

Clostridium perfringens↗

PubMed1975

The effect of staphylococcal enterotoxins on the primary in vitro immune response.

Staphylococcal enterotoxins, like several plant lectins, have been shown to stimulate mitogenic activity and lymphokine production in lymphocytes. The effect of enterotoxins A and B on the primary in vitro plaque-forming cell (PFC) response of mouse (C57BL/6) spleen cells to sheep red blood cells (SRBC) was examined. PFC responses in 4- or 5-day cultures were inhibited greater than 90% by 0.1 mug enterotoxin A and by 3- to 6-mug enterotoxin B when the toxins were added to the cultures either at the time of SRBC addition or 24 hr before. Both enterotoxins A and B were shown to be T lymphocyte mitogens. Kinetic data indicated that the enterotoxins (10 mug) inhibited the PFC response as early as day 3, but were relatively more inhibitory at days 4 and 5. The PFC response was inhibited when enterotoxins were added to cultures at the same time as antigen or a day later; it was enhanced when added at day 2; and it was unaffected when added at day 3 of 4-day cultures. Further, the presence of enterotoxin A during the first 24 hr of culture and subsequent removal was still as effective in inhibiting the PFC response as when it was present throughout the culture period. The PFC inhibitory properties of enterotoxins appear, then, to affect some early event(s) in the in vitro immune response. Alpha-methyl-D-mannopyranoside blocked the PFC inhibitory effect of concanavalin A (con A), but it had no effect on enterotoxin A. The two mitogens appear, then, to react with different receptors on the lymphocytes or to differ in the dynamics of their reactivity. The effects of staphylococcal enterotoxins on the PFC response of spleen cells were remarkably similar to those reported for lectins such as con A. Enterotoxins are structurally simpler than con A and should therefore be quite useful in studying various biologic activities of lymphocytes.

Animals↗

PubMed1974

Polymyxin B-Induced Release of Low-Molecular-Weight, Heat-Labile Enterotoxin from Escherichia coli.

Polymyxin B-induced release of enterotoxin from Escherichia coli strain H-10407 was demonstrated. Incubation of E. coli cells derived from 6-h cultures with polymyxin caused the rapid release of enterotoxin with a molecular weight of approximately 20,000, as estimated by the gel filtration technique. The rapidity of the release of enterotoxin indicates that it probably resides in the periplasmic space of the cell. The low-molecular-weight enterotoxin possessed vascular permeability factor and diarrheagenic activities, both of which were found to be heat-labile. The permeability factor activity of this enterotoxin was neutralized by antisera prepared against crude E. coli enterotoxin, Vibrio cholerae enterotoxin (choleragen), and V. cholerae toxoid (choleragenoid), respectively. Supernatant fluids of 6-h E. coli cultures did not contain this molecular form of enterotoxin but did contain very high-molecular-weight, heat-labile enterotoxin. Incubation of cells derived from older (18 h) cultures with polymyxin caused the release of both low- (20,000) and high-molecular-weight forms of enterotoxin. We concluded that either the 20,000-dalton form of heat-labile enterotoxin is not released by E. coli under in vitro growth conditions or that enterotoxin released in this form is rapidly destroyed or inactivated.

Journal Article↗

PubMed1988

Structural analysis of staphylococcal enterotoxins B and C1 using circular dichroism and fluorescence spectroscopy.

Secondary and tertiary structural parameters of two functionally and serologically related proteins, staphylococcal enterotoxins B and C1, have been determined by using circular dichroism and fluorescence spectroscopy. The secondary structures derived from the respective far-UV circular dichroic spectra were 9.5% alpha-helix, 55.0% beta-pleated sheets, 16.5% beta-turns, and 19.0% random coils for enterotoxin B and 15.0% alpha-helix, 38.0% beta-pleated sheets, 25.5% beta-turns, and 21.5% random coils for staphylococcal enterotoxin C1. The values matched well with the secondary structures derived from the amino acid sequences (Chou and Fasman method). Seven antigenic sites have been predicted for both staphylococcal enterotoxins B and C1 by using the hydrophilicity and the secondary structure information. Three of these antigenic sites appear similar. Fluorescence quantum yield of the single tryptophan residue (Trp-197) of both the enterotoxins showed the tryptophan residue in staphylococcal enterotoxin B to be approximately 46% more fluorescent than in staphylococcal enterotoxin C1. Tryptophan fluorescence quenching by the surface quencher I- and the neutral quencher acrylamide revealed that the single tryptophan residue in each of the enterotoxins is buried in the protein matrix and is not accessible to the surface quencher I-. The tryptophan residue in staphylococcal enterotoxin C1 is 14% less accessible to acrylamide than in staphylococcal enterotoxin B. The data, in general, reflect several similarities and significant differences between the two related enterotoxins.

Amino Acid Sequence↗

PubMed1992

Enterotoxin residues determining T-cell receptor V beta binding specificity.

Superantigens such as the staphylococcal enterotoxins bind to major histocompatibility complex (MHC) class II molecules and activate T cells through a specific interaction between the V beta region of the T-cell antigen receptor (TCR) and the toxin. The TCR beta-chain alone is sufficient to produce the interaction with the enterotoxin-class II complex. Identification of the regions of enterotoxins that interact with TCR has so far proved equivocal because of difficulties in distinguishing between direct effects on T-cell recognition and indirect effects resulting from alteration of binding to class II. For example, amino-terminal truncations of SEB abrogated T-cell stimulation whereas carboxy-terminal truncation of SEA stopped its mitogenic activity. The most comprehensive study to date, accounting for both enterotoxin binding to class II and enterotoxin interactions with the TCR, identified two functionally important regions for SEB binding to TCR. Although the amino-acid sequences of staphylococcal enterotoxins A and E are 82% identical, they activate T cells bearing different V beta elements. We have assayed the binding of cells coated with these enterotoxins to soluble secreted TCR beta-chain protein and find that V beta 3 binds enterotoxin A but not E, whereas V beta 11 binds enterotoxin but not A. To map the amino-acid residues responsible for these different binding specificities, we prepared a series of hybrids between the two staphylococcal enterotoxins. We report that just two amino-acid residues near the carboxy terminus of the enterotoxins are responsible for the discrimination between these molecules by V beta 3 and V beta 11.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed2006

Prevalence of enterotoxin and toxic shock syndrome toxin genes in Staphylococcus aureus isolated from milk of cows with mastitis.

Staphylococcus aureus isolated from milk of cows with mastitis were evaluated for the prevalence of 16 enterotoxin genes (sea-see and seg-seq) and toxic shock syndrome toxin gene (tsst-1). Of 78 S. aureus examined, 73 (93.6%) were positive for one or more enterotoxin genes and these were divided into 36 groups by the presence of different enterotoxin genes. Enterotoxin genes including sen (84.6%), sem (71.8%), sei (60.3%) and sed (52.6%) were found frequently, while seg (24.4%), seq (16.7%), seo (12.8%), and seb (1.3%) were found at lower frequencies. Toxic shock syndrome toxin (tsst-1) gene was detected in 20 (25.6%) isolates and was always found in combination with other enterotoxin genes. The majority (88.5%) harbored more than one enterotoxin gene in different combinations. Eight S. aureus isolates (10.3%) were positive for sed, sei, sem, and sen; six (7.7%) possessed sed, seg, sei, sem, sen, and tsst-1; five (6.4%) had sei, sem, and sen; and four (5.1%) had sei, and sen. One isolate was positive for seb along with other SE genes including sed, seh, sem, sen, seq, and tsst-1. None of the isolates carried other enterotoxin genes (sea, sec, see, sej, sek, sel, and sep). PFGE profiles revealed 15 distinct pulsotypes among the 78 S. aureus isolates evaluated. PFGE and enterotoxin gene profiles did not match with each other because a single pulsotype carried different combinations of enterotoxin genes. The majority of S. aureus isolated from milk of mastitic cows carried newly described SE genes sem, sen and sei along with classical SE genes, sed and tsst-1. This is the first report describing the high prevalence of newly described enterotoxin genes, sem and sen in S. aureus from bovine mastitis. The high prevalence of enterotoxin genes and tsst-1 in S. aureus may be important as it is relevant to udder pathogenicity and food hygiene.

Animals↗

PubMed1999

Studies on the functional site on staphylococcal enterotoxin A responsible for production of murine gamma interferon.

To identify the functional region(s) associated with induction of gamma interferon on the staphylococcal enterotoxin A molecule, native staphylococcal enterotoxin A molecules and 12 various synthetic peptides corresponding to different regions of entire staphylococcal enterotoxin A were compared to induce gamma interferon production in murine spleen cells. The native staphylococcal enterotoxin A molecule induced gamma interferon production, whereas all of the 12 synthetic peptides did not. Pre-treatment of the murine spleen cells with synthetic peptide A-9 (corresponding to amino acid residues 161-180) significantly inhibited the staphylococcal enterotoxin A-induced gamma interferon production, whereas those with other synthetic peptides did not. When native staphylococcal enterotoxin A was pre-treated with either anti-staphylococcal enterotoxin A serum or anti-peptide sera, anti-staphylococcal enterotoxin A serum and antisera to peptides A-1 (1-20), A-7 (121-140), A-8 (141-160), A-9 (161-180) and A-10 (181-200) inhibited the staphylococcal enterotoxin A-induced gamma interferon production. From these findings, the amino acid residues 161-180 on the staphylococcal enterotoxin A molecule may be an essential region for murine gamma interferon production. Furthermore, the neutralizing epitopes may be also located on regions of amino acid residues 1-20, 121-140, 141-160 and 181-200 on the staphylococcal enterotoxin A molecule.

Amino Acid Sequence↗

PubMed1993

Amino acid sequence of heat-labile enterotoxin from chicken enterotoxigenic Escherichia coli is identical to that of human strain H 10407.

The DNA sequence of heat-labile enterotoxin from the chicken enterotoxigenic Escherichia coli 21d strain was determined by direct dideoxy sequencing of polymerase chain reaction (PCR)-amplified DNA and was compared with those of heat-labile enterotoxins from porcine and human enterotoxigenic E. coli strains EWD 299 and H 10407. The structural genes of the A and B subunits of chicken heat-labile enterotoxin were identical to those of human heat-labile enterotoxin from the human H 10407 strain. Moreover, 67 base pairs of the upstream and 60 base pairs of the downstream region of the chicken heat-labile enterotoxin gene were also identical to that of the human heat-labile enterotoxin from strain H 10407. However, the patterns of plasmids from the 21d and H 10407 strains were different. The 21d strain had no band corresponding to the 42-MDa plasmid of the H 10407 strain encoding the heat-labile enterotoxin gene but it had a smaller plasmid. These data suggest that although the DNA sequence of chicken heat-labile enterotoxin is identical to that of human heat-labile enterotoxin, the plasmid encoding the chicken heat-labile enterotoxin gene in the chicken might be different from that encoding the human heat-labile enterotoxin gene in the H 10407 strain.

Amino Acid Sequence↗

PubMed1995

Proteolytic activity of the Bacteroides fragilis enterotoxin causes fluid secretion and intestinal damage in vivo.

Strains of Bacteroides fragilis that produce an enterotoxin have been implicated in diarrheal disease in farm animals and humans during the past decade. Our laboratory has purified and characterized this enterotoxin as a single polypeptide (M(r), approximately 20,000). Recently, we used PCR to clone and sequence the enterotoxin gene from B. fragilis and showed that it exhibits significant homology with extracellular metalloproteases. Further studies showed that the purified enterotoxin has protease activity. To further characterize the role of this enterotoxin in diarrheal disease, we studied the histological and pathological effects of highly purified B. fragilis enterotoxin in lamb, rabbit, and rat ligated intestinal loops. When the enterotoxin was injected into ligated ileal and colonic loops, there was significant tissue damage and subsequent fluid accumulation. The fluid response in the ileum was greater in lambs than in rabbits and rats, whereas the fluid response in the colon was greater in rabbits than in lambs and rats. Analysis of the intestinal fluid elicited by the enterotoxin revealed an accumulation of chloride and sodium as well as albumin and total protein. Histological examination revealed mild necrosis of epithelial cells, crypt elongation, villus attenuation, and hyperplasia. There was extensive detachment and rounding of surface epithelial cells and an infiltration of neutrophils. Enterotoxic activity was inhibited by the metal chelators EDTA and 1,10-phenanthroline; to some degree, the enterotoxic activity could be reconstituted by the addition of zinc to the chelated enterotoxin. Our results indicate that the enterotoxin elicits a significant fluid response subsequent to tissue damage in the small and large intestine. These data further support the idea that this enterotoxin is an important virulence factor in B. fragilis-associated diarrhea.

Animals↗

PubMed1973

Production of staphylococcal enterotoxins A, B, and C under conditions of controlled pH and aeration.

The production of enterotoxins A, B, and C by nine strains of Staphylococcus aureus has been studied under controlled conditions in a fermenter. The strain to strain differences between staphylococci producing a specific enterotoxin were very marked. Increasing aeration in shake flasks improved both growth and production of all extracellular proteins measured other than that of enterotoxin C, the yield of which was decreased in one strain at high aeration. Silicone antifoam decreased the production of extracellular proteins, although enterotoxin A production from three strains was much less affected than that of enterotoxins B and C. In a detailed study of three strains, production of enterotoxins A and C was considerably greater in a defined amino acid medium than in a casein hydrolysate medium and was optimal for all three enterotoxins between pH 6.5 and 7.3. Changes in the pH or medium used in the fermenter that led to increased enterotoxin production could generally be correlated with a change in growth pattern, showing an extended transition period from exponential to stationary phase. Three out of five enterotoxin-A producing strains produced significantly more enterotoxin at a controlled pH of 6.5 in the fermenter than in shake-flask cultures. The yields with strain 100 were about five times greater than hitherto reported. Since many foods are buffered at pH 6 to 6.5, some strains may, therefore, produce sufficient enterotoxin A to cause food poisoning, although little or none may be produced when grown under normal testing procedures.

Bacterial Proteins↗

PubMedDate not supplied

[Studies of the enterotoxin production capacity of L forms derived from enterotoxic strains of Staphylococcus aureus].

The production of enterotoxin by L-forms obtained from strains of Staphylococcus aureus (10 enterotoxin A-producing strains, 7 enterotoxin B, 2 enterotoxin C and 1 which produced both enterotoxins A and C) has been studied by agar-gel diffusion technique. Using a proper technique, enterotoxin could be detected for 4 L-forms; 3 of these produced the same enterotoxin as parent strain (2 enterotoxin A and 1 enterotoxin B). As regards the other L-form, obtained from strain of St. Aureus which produced both enterotoxins A and C, only enterotoxin A could be detected.

Enterotoxins↗

PubMed1981

Analysis of the near-ultraviolet circular dichroic spectra of staphylococcal enterotoxins A, B and C.

The near-ultraviolet CD spectra from 260 to 300 nm of staphylococcal enterotoxins A, B and C were resolved empirically into Gaussian curves. Each spectrum contained the same six components with maximum ellipticities at virtually identical wavelengths. The rotatory strength of the bands of enterotoxin A, however, differed significantly from that of enterotoxins B and C. Each Gaussian curve was identified as corresponding to a prominent CD transition of an aromatic chromophore: two phenylalanine bands from its 1Lb transition (0-0 and 0 + 930 cm-1); four tyrosine bands from its 1Lb transition (the 800 cm-1 primary vibronic progression) with the weakest of these overlapping a phenylalanine band; and one 1Lb tryptophan band. At alkaline pH, tyrosylate CD bands arose, centered at 247-249 nm and at 295-298 nm. The intensity of the 295-298 nm bands indicated that most of the tyrosine CD in the neutral enterotoxins was contributed by buried residues. The tryptophan contribution to the CD of enterotoxin A was positive, while that of B and C was negative. Also indicative of a different milieu was the ready oxidation of the A toxin by N-bromosuccinimide and the unavailability of the single tryptophan residue in the other two toxins to this reagent. The environment of the disulfide bond was markedly diverse in the three enterotoxins. Enterotoxin C was refractory to reduction by mercaptoethanol under conditions where enterotoxins B and A were readily reduced. The contribution of the disulfide of enterotoxin B to its CD spectrum was positive with an intensity of about 9000 deg . cm2 . dmol-1 and was centered near 273 nm. The difference spectrum between native and reduced enterotoxin A was much smaller and appeared to be conformational in origin.

Circular Dichroism↗

PubMed2005

Distribution of newly described enterotoxin-like genes in Staphylococcus aureus from food.

Extensive analysis of the Staphylococcus aureus genome has allowed the identification of new genes encoding enterotoxin-like superantigens (SEls). Some of these are thought to be involved in staphylococcal food poisoning, while others do not elicit any emetic effect. The potential impact of these members of the enterotoxin-like family on the human organism seems to rely mainly on their superantigenic activity. In this paper the distribution of the genes coding for enterotoxin-like superantigens in S. aureus isolated from food was studied. Fifty isolates of S. aureus were examined and 27 were shown to be enterotoxigenic. Only 9 of the 27 strains carried genes encoding enterotoxins SEA-SEE. In 18 SEA-SEE-negative strains the presence of newly described enterotoxin genes was detected. All SEA-SEE-positive strains simultaneously carried genes of new SEls. We show that the gene encoding SElH (staphylococcal enterotoxin-like enterotoxin H) was the most frequently detected (n=14), while genes encoding SElI together with SElG accompanied by the other genes of the egc locus were detected in three strains. We also detected the presence of three less investigated genes: sep, sel, and sek. These genes were present in eight, two, and one isolate, respectively. In one strain, sep was accompanied by genes of other SEls, while in the remaining seven it was the only enterotoxin-like gene detected. The high prevalence of newly discovered enterotoxin genes, including the genes encoding emetic toxins, was demonstrated in food-derived strains. This supports the need for additional work on its role in food poisoning and, alternatively, to monitor its presence in S. aureus isolated from food. Our results suggest that yet unknown genetic elements encoding enterotoxin genes may exist.

Base Sequence↗

PubMed1988

Immunogenic and antigenic characteristics of Salmonella heat-labile enterotoxin.

The intramuscular immunization of rabbits with enterotoxin of S. weltevreden failed to provide protection against challenges with homologous Salmonella enterotoxin as well as heterologous enterotoxins (cholera toxin or E. coli LT). Similar results were obtained in rabbits immunized with cholera toxin, choleragenoid and E. coli LT. However, Salmonella antitoxin contained neutralizing antibodies against Salmonella enterotoxin (but not against cholera toxin) and thus was capable of neutralizing Salmonella enterotoxin when tested for skin permeability reaction. Immunodiffusion experiments showed that antitoxin prepared against the enterotoxin of one of the strains of S. weltevreden formed precipitin bands with enterotoxin preparations of 5 strains of S. weltevreden and 2 strains of S. anatum. However, Salmonella antitoxin failed to form precipitin bands with enterotoxins of other heterologous Salmonella species (S. dublin, S. enteritidis, S. hindmarsh and S. newport), cholera toxin and E. coli LT. The immunoelectrophoretic studies corroborated the results obtained by double immunodiffusion experiments. However, both Salmonella and cholera toxins migrated electrophoretically toward the cathode and resembled globulin in this respect. Salmonella enterotoxin, though immunogenic, yet proved unprotective through the parenteral route and appears to be antigenically distinct from cholera and E. coli enterotoxins.

Animals↗

PubMed1986

Detection of staphylococcal enterotoxins by enzyme-linked immunosorbent assays and radioimmunoassays: comparison of monoclonal and polyclonal antibody systems.

Murine monoclonal antibodies reactive with at least one of the serological types of staphylococcal enterotoxin were examined for use in assay systems for the detection of enterotoxin at the level of 1.0 ng of enterotoxin per ml. An antibody sandwich enzyme-linked immunosorbent assay was devised for each toxin type by identifying an effective antibody pair. One antibody (the coating antibody) was coated onto a polystyrene plate and removed the enterotoxin from the test solution; the second antibody (the probing antibody) was conjugated to horseradish peroxidase and detected the captured toxin. Enterotoxins A and E could be detected in the same system by the use of cross-reacting monoclonal antibodies. All subtypes of enterotoxin C could be detected in one assay system. Two effective systems were described for each of types B and D. Each of these systems, when compared with the homologous enterotoxin-specific polyclonal rabbit antibody systems, was found to compare favorably. The monoclonal enzyme-linked immunosorbent assay systems for the detection of enterotoxins A and C2 were examined for a variety of food extracts; no abnormal interference could be detected from these extracts. The monoclonal antibody systems were also compared with the homologous enterotoxin-specific polyclonal serum for the detection of enterotoxin by the competitive radioimmunoassay (RIA). Single monoclonal antibodies generally did not perform as well in the RIA as did the homologous toxin-specific polyclonal serum. However, pools of monoclonal antibodies were prepared that approached the sensitivity and precision of the polyclonal system for the detection of each toxin by the RIA.

Animals↗

PubMed1995

Identification and purification of a new staphylococcal enterotoxin, H.

A staphylococcal enterotoxin which elicited an emetic response in monkeys but did not share antigenic determinants with any of the identified enterotoxins was identified and purified from Staphylococcus aureus FRI-569. The emetic activity of this new enterotoxin was neutralized only by antibodies specific to it and not by antibodies to enterotoxins A, B, C, D, and E or toxic shock syndrome toxin 1. Immunodiffusion assays did not detect cross-reactivity between this new and all the other identified enterotoxins. The purification procedure involved removal of the enterotoxin from culture supernatant fluids by batch adsorption with CG-50 resin, CM-Sepharose FL ion-exchange chromatography, and Sephacryl 100 HR and Bio-Gel P-30 gel filtration. The molecular weight of this enterotoxin, 27,300, determined by gel filtration on Sephacryl 100 HR agreed with the molecular weight, 28,500, determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The apparent migration of this enterotoxin determined by SDS-PAGE did not shift in the presence of a disulfide reducing agent, indicating that it is composed of a single-chain protein. The N-terminal amino acid sequence of the enterotoxin was determined to be Glu-Asp-Leu-His-Asp-Lys-Ser-Glu-Leu-Thr-Asp-Leu-Ala-Leu-Ala-Asn-Ala-Tyr- Gly- Gln-Tyr-Asn-His-Pro-Phe-Ile-Lys-Glu-Asn-Ile, which did not match the N-terminal sequences of any known proteins. The isoelectric point of the enterotoxin determined by isoelectric focusing was about 5.7.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1978

Interaction of polymorphonuclear neutrophils with Escherichia coli. Effect of enterotoxin on phagocytosis, killing, chemotaxis, and cyclic AMP.

Enterotoxigenic Escherichia coli are associated with noninflammatory diarrhea and stimulate adenylate cyclase activity of mammalian cells, thereby increasing intracellular cyclic adenosine 3',5'-monophosphate (cyclic AMP). Increased concentrations of cyclic AMP in polymorphonuclear neutrophils (PMN) inhibit phagocytosis, candidacidal activity, granule discharge, and chemotactic responsiveness. We examined the effect of enterotoxin on the interaction of human PMN with E. coli. Enterotoxigenic and nonenterotoxigenic strains, including serotypes of E. coli identical except for the presence or absence of the plasmid coding for enterotoxin production, were utilized. Enterotoxigenic and nonenterotoxigenic E. coli, tumbled with PMN, were phagocytized and killed (>97%) equally well, and these strains stimulated PMN hexose monophosphate shunt activity equivalently.However, a chemotaxis assay under agarose demonstrated that filtrates of 10 enterotoxigenic strains were less chemotactic for PMN by 15+/-2% total migration or 46+/-1% directed migration, when compared with 6 non-enterotoxigenic strains (P < 0.001). Inactivation of the enterotoxin by heat (65 degrees C for 30 min) or antibodies formed to E. coli enterotoxin eliminated the inhibitory effect of the enterotoxic filtrates for PMN chemotaxis. Addition of purified E. coli enterotoxin directly to the PMN decreased chemotaxis to E. coli filtrates by 32+/-2% (P < 0.001). These data suggest that the effect was due to the heat-labile enterotoxin. The phosphodiesterase inhibitor, 1-methyl-3-isobutylxanthine (0.1 mM), which potentiates effects due to an increase in intracellular cyclic AMP, further decreased total PMN migration (random plus directed) toward enterotoxic filtrates to 46% of that to nonenterotoxic filtrates (P < 0.001). Addition of cholera toxin (1 mug/ml), which is similar to E. coli enterotoxin, to the PMN inhibited total migration toward nonenterotoxic filtrates by 16+/-2% (P < 0.001). Exogenous dibutyryl cyclic AMP (2 mM) inhibited total PMN migration toward E. coli filtrates by 32% (P < 0.001). PMN intracellular cyclic AMP levels increased by 220% after 2 h of incubation with purified E. coli enterotoxin. The decreased chemotactic attractiveness of enterotoxic E. coli filtrates appears to be related to the ability of enterotoxin to increase cyclic AMP in PMN. Enterotoxin production by E. coli may be advantageous to the microbe by decreasing its chemotactic appeal for PMN.

Blood Bactericidal Activity↗

PubMed1982

An enterotoxin-like protein in Staphylococcus aureus strains from patients with toxic shock syndrome.

An enterotoxin-like protein, tentatively labeled enterotoxin F, was isolated from Staphylococcus aureus strains taken from patients with toxic shock syndrome. Antibodies specific for enterotoxin F were prepared in rabbits. Use of these antibodies showed that 130 (91.5%) of 142 S. aureus strains from patients with toxic shock syndrome produced enterotoxin F. Strains from toxic shock patients in eight other countries were identified as enterotoxin F producers. Only a small number of S. aureus strains from sources other than patients with toxic shock syndrome were found to produce enterotoxin F. Twenty-one of 111 controls had low antibody titers (less than 1:100) to enterotoxin F whereas 86 of 92 toxic shock patients had low acute phase antibody titers (less than 1:100) to enterotoxin F. Eight of 52 patients had serum conversion as shown by an increase in antibody titer to enterotoxin F in sera taken 21 to 60 days after onset of the illness. It may be possible to identify persons susceptible to toxic shock syndrome by measuring their antibody titer to enterotoxin F.

Bacterial Toxins↗