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PubMed1992

Evaluation of Biken test for detection of Salmonella enterotoxin.

Biken test by using antiserum to purified Salmonella enterotoxin (SE) was standardized and carried out to screen salmonellae for their enterotoxigenicity. As many as 101 strains of Salmonella belonging to 15 different serotypes isolated from foods of animal origin were subjected to Biken test. Of these, 68 (67.32%) were found seropositive. The test correlated with the rabbit ligated ileal loop (RLIL) test completely for the detection of enterotoxin producing salmonellae with 24 test strains. However, 5 of the 13 strains which were negative in the RLIL test, yielded positive results with the Biken test.

Animals↗

PubMed1992

Myoelectric activity of the small intestine in enterotoxin-induced diarrhea of calves.

Electrodes were surgically implanted at 15-cm intervals in the jejunum and ileum of 4 healthy neonatal calves so that myoelectric activity could be recorded on 2 consecutive days. On the first day, each calf received a control treatment, and myoelectric activity was recorded for 340 minutes. Phase I was recorded for a mean of 175.8 +/- 22.8 minutes (51.5%), phase II for 124 +/- 27.4 minutes (36.5%), and phase III for 40.3 +/- 6 minutes (11.9%). On the second day, each calf was treated with approximately 200 micrograms of heat-stable enterotoxin (STa) of Escherichia coli orally. All calves developed diarrhea after the administration of STa. Phase I was recorded for a mean of 92.5 +/- 42.3 minutes (27.2%), phase II for 227.3 +/- 52.5 minutes (66.9%), and phase III for 20.3 +/- 11.4 minutes (6.0%). Increase in phase II and decrease in phases I and III after STa administration were significant (P less than 0.05). Duration of the migrating myoelectric complex was longer after STa administration (median, 64 minutes), compared with the control treatment (median, 54 minutes). Minute rhythms, recorded on the day of toxin administration, ranged from 49 to 153 minutes. There was no difference between the number of migrating action potential complexes on the control days (range, 1 to 10), compared with those on treatment days (range, 1 to 14). These findings are suggestive that enterotoxin-induced diarrhea of calves is accompanied by increased total spiking activity and minute rhythms in the distal portion of the jejunum and ileum.

Animals↗

PubMed1992

[Detection of enterotoxin production in bovine Salmonella isolates].

54 Salmonella-strains (7 serovars) of bovine origin isolated from faecal samples, rectal swabs as well as from organs of emergency-slaughtered or dead animals were tested for enterotoxin production (heat-labile and heat-stable) in rabbit-ileal-loop-assay (RILT), skin-permeability-factor-test (HPT), CHO- and Y1-cell-culture-assay and in baby-mouse-test (BMT). The cell-free supernatants (CFS) were used in the tests. The Y1-cells did not respond to the Salmonella toxins. While the RILT was suitable, the CHO-cell-assay proved to be the most sensitive and easy-to-handle system. The results confirm the frequent occurrence of the biological property of enterotoxin production within the species Salmonella enterica. Therefore, this property is in our opinion not useful as an epizootological marker for salmonellae.

Animals↗

PubMed1992

Raw milk as a source of enterotoxigenic Staphylococcus aureus and enterotoxins in consumer milk.

Staphylococcus aureus strains were isolated from 183 of 300 raw milk samples collected at the Kenya Co-operative Creamery (Dandora). 97 of these 183 trains were assayed for the production of enterotoxin A, B, C and D. Seventy two (74.2%) of these were found to produce either a single or a combination of enterotoxins. Raw milk is a potential source of enterotoxigenic S. aureus in milk and milk products, especially if there is defective pasteurisation.

Animals↗

PubMed1992

[Cloning and expression of the gene for Escherichia coli thermostable enterotoxin].

Gene estA coding for thermostable enterotoxin of Escherichia coli has been cloned. It is shown that in the E. coli strain SA162 this gene is located on the chromosome. Using polymerase chain reaction a site-directed mutagenesis of the cloned gene has been carried out, resulted in a recombinant strain--producer of the thermostable enterotoxin.

Amino Acid Sequence↗

PubMed1992

Staphylococcal enterotoxin-mediated human T-T cell interactions.

Staphylococcal enterotoxins (SE) are known to stimulate a large proportion of T cells. SE bind to MHC-class II molecules on APC and a particular segment of certain TCR V beta and V gamma gene products. Resting human T cells do not express HLA class II Ag and therefore cannot present SE to T cells. Activated human T cells, however, do express HLA-DR, -DP, and -DQ Ag and could consequently serve as APC for SE. As such, local immune responses to SE might be regulated and/or abrogated by SE-mediated T-T cell interactions leading to T cell destruction. We have investigated if such SE-mediated T-T cell interactions can occur in vitro using human cytolytic TCR-alpha beta+ and TCR-gamma delta+ T cell clones. We demonstrate that the TCR-alpha beta+ T cell clones can efficiently present staphylococcal enterotoxin A (SEA) to each other: T cell clones coated with SEA are lysed by SEA-reactive T cell clones but not by a SEA-nonreactive T cell clone. Furthermore, the SEA-reactive TCR-alpha beta+ clones (but not the SEA-nonreactive clone) destruct themselves in the presence of SEA at low concentrations of SEA (less than 0.01 microgram/ml). Also, SEA-coated T cell clones can induce proliferative responses although such responses are much weaker than those induced when B cells are used as stimulator cells. In contrast, the SEA-reactive TCR-gamma delta+ T cell clones are resistant to autokilling in the presence of SEA and they do not lyse SEA-coated TCR-gamma delta+ targets. However, such targets can be lysed by TCR-alpha beta+ effector cells. These results indicate that TCR-gamma delta+ cells are relatively resistant to lysis and that during local nonspecific immune responses triggered by SE, which induces HLA-class II expression by the responding T cells, SE-mediated T-T cell interactions may play a role in the regulation and/or abrogation of these immune responses.

Antigens, Bacterial↗

PubMed2004

[Large-scale, acute, bacterial gastroenteritis caused by the enterotoxin of Staphylococcus aureus after a barbecue].

UNLABELLED: EPIDEMIOLOGICAL OBSERVATION: On a warm day, during a barbecue that was attended by over 100 guests, a large number became rapidly ill with signs of acute gastroenteritis within a few hours after eating the prepared food. The characteristic symptoms were nausea, vomiting, syncope and in some cases in a later stage, diarrhoea. Sixty patients were transferred to hospitals. INVESTIGATION: Investigation revealed that the cause of this outbreak of gastroenteritis was an enterotoxin-A-producing strain of Staphylococcus aureus in a noodle dish. Both the food residues and the faeces from patients contained genotypically identical strains of S. aureus. They all had the gene for the gastroenteritis-inducing enterotoxin A from S. aureus. CONCLUSION: This case shows that the timely involvement of the different health authorities responsible for intervening in explosions of food poisoning is crucial for the clarification and treatment of such large-scale outbreaks. In the investigation of this outbreak, the municipal health authority co-operated with regional laboratories and the Food and Consumer Product Safety Authority/Inspectorate for Health Protection and Veterinary Public Health.

Acute Disease↗

PubMed2004

[Molecular microbiology and clinical features of Staphylococcus aureus enterotoxins].

The authors review the novel data available in the literature and their experimental results about the enterotoxins of Staphylococcus aureus. Their genetics, phylogenetics, biological characteristics, as well as mechanisms of action are dealt with. Furthermore, pathogenesis, pathomechanism, immunology, major symptoms and signs, diagnostics, management, possible outcomes, and epidemiology of the Staphylococcus aureus enterotoxin-associated human diseases are hereby reviewed.

Bacterial Toxins↗

PubMed2004

Cloning and expression of Vibrio cholerae virulence gene, accessory cholera enterotoxin (ace).

The cholera enterotoxin (CT) has been considered a major virulence factor of Vibrio cholerae. The accessory cholera enterotoxin (ace) gene is the third gene of V. cholerae virulence cassette. The gene coding for the Ace toxin was amplified from V. cholerae isolates producing a single band of 314 bp. The presence of ace gene was confirmed by hybridization as well as by sequencing. The gene was successfully expressed in Escherichia coli (LMG194) using expression, pBAD/Thio-TOPO vector. Optimal conditions for expression included choice of host strain, temperature used for culturing, and concentration of antibiotic and arabinose inducer. The Ace protein was obtained from the cell supernatant as a fusion protein with a molecular mass 34 kDa which was detected using an anti V5-HRP epitope tagged antibody.

Base Sequence↗

PubMed2005

[Comparison of antimicrobial resistance patterns of enterotoxin gene positive and negative Bacteroides fragilis isolates].

Some of the Bacteroides fragilis strains produce enterotoxin named fragilysin which is accepted as a virulence factor. In this study, the presence of enterotoxin genes (bft) in clinical B. fragilis strains has been investigated and the antimicrobial resistance patterns of bft positive and negative isolates have been compared. B. fragilis strains isolated from different clinical samples were identified by conventional methods and API 20A system, and the presence of bft genes were searched by using BF3/BF4 primers in polymerase chain reaction. A total of 100 B. fragilis strains of which 50 bft gene positive and 50 bft gene negative were included to the study, and their antimicrobial susceptibilities were determined by agar dilution method as recommended by NCCLS (M11-A4). Of 100 strains, 71 (34 bft negative, 37 bft positive) have been isolated from the stool, and 29 (16 bft negative, 13 bft positive) have been isolated from other specimens (blood, abscess, pleural and peritoneal fluids). beta-lactamase production was detected in 96% of enterotoxigenic B. fragilis (ETBF) and 95% of non-toxigenic strains, and all tested strains were found to be susceptible to amoxicillin/clavulanic acid, imipenem and metronidazole. The resistance rates (with MIC90 values) of bft positive isolates against the other antibiotics were as follows; 96% (256 microg/ml) for ampicillin, 16% (256 microg/ml) for piperacillin, 8% (32 microg/ml) for cefoxitin, 24% (> 256 microg/ml) for clindamycin, 74% (64 microg/ml) for tetracycline and 0% (8 microg/ml) for chloramphenicol. These rates were found as follows for bft negative strains; 95% (256 microg/ml) for ampicillin, 6% (64 microg/ml) for piperacillin, 6% (32 microg/ml) for cefoxitin, 38% (> 256 microg/ml) for clindamycin, 64% (64 microg/ml) for tetracycline and 4% (8 microg/ml) for chloramphenicol. Although the resistance rates and MIC90 values of bft positive strains against the antimicrobials seemed to be higher, there were no statistically significant differences between resistance rates of bft positive and negative strains (P > 0.05; 0.12 and 0.28, respectively).

Anti-Bacterial Agents↗

PubMed1991

[The use of the aggregate hemagglutination reaction and immunoenzyme analysis in determining staphylococcal enterotoxin type D].

Type D purified staphylococcal enterotoxin and anti-enterotoxic serum to it were prepared. IgG isolated from the anti-enterotoxic serum by the affinity chromatography method was used to improve the specificity and sensitivity of the aggregate hemagglutination test (AHAT) and enzyme immunoassay (EIA). The developed AHAT and EIA variants intended for the indication of type D staphylococcal enterotoxin are characterized by a high resolution ability and strict specificity. The suggested methods are simple and may be used for the rapid diagnosis of staphylococcal toxin infections.

Enterotoxins↗

PubMed1976

The effect of enterotoxin of Clostridium welchii (perfringens) type A on fowls.

Lethal doses of enterotoxin of Clostridium welchii (perfringens) type A injected intravenously into young fowls caused immediate lassitude, with partial recovery, followed by death seven to 35 h after inoculation. Lesions found were ascites, hydropericardium, oedema of the muscles, hepatic congestion, urate deposits on the peritoneum and the pericardium, and intestinal hyperaemia. Sublethal doses produced no clinical signs or lesion. The LD50 of this enterotoxin was 74-84 mug/kg of body weight.

Animals↗

PubMed1991

[The effect of the synergistic action of enterotoxin on the specific protective complex of Shigella sonnei].

The study has first established that enterotoxin enhances the protective potency of S. sonnei specific protective complex. This effect has been revealed both in experiments of the oral immunization of mice and in experiments of the conjunctival immunization of guinea pigs and depends on the dose of enterotoxin used in the experiment. The increase of protection has a specific character. These observations open prospects for further enhancement for the protective properties of S. sonnei specific protective complex, which should be taken into consideration in developing the vaccinal preparation.

Animals↗

PubMed1991

Mutation of the disulfide loop in staphylococcal enterotoxin A. Consequences for T cell recognition.

The hallmark of T cell responses to staphylococcal enterotoxins (SE) and other super-Ag is a selective stimulation of cells expressing particular TCR-V beta segments. Our previous studies suggested that the disulfide loop in SE is critical for their interaction with the TCR. To investigate this concept in further detail we constructed disulfide loop mutants of staphylococcal enterotoxin A (SEA), and examined these altered toxins for mitogenicity, class II MHC binding, and V beta specificity. We found that substitutions of either Cys-96 or Cys-106 decreased mitogenicity by 100-fold without significantly affecting class II binding or resistance of the molecule to proteolysis. Several mutants lost the capacity to stimulate V beta 11+ cells, except a Cys-106----Gln mutant for which V beta 11-stimulatory activity was increased. By contrast, mutants containing Cys----Ala substitutions acquired the capacity to stimulate V beta 6+ cells. Despite these effects of V beta specificity, all mutants retained the predominant preference of SEA for V beta 3+ cells. Neither exchange of regions flanking the loop in SEA with corresponding residues in SEB, nor conversion of the entire loop region of SEA to that of SEE, were associated with transfers of V beta specificity. Our results suggest that the disulfide loop in SEA contributes to toxin avidity for the TCR, rather than specificity for particular V beta.

Amino Acid Sequence↗

PubMed1991

Guinea-pig ileal loop assay: a better replacement of the suckling mouse assay for detection of heat-stable enterotoxins of Escherichia coli.

The suitability of guinea-pig ileal loop assay (GILA) for the assay of heat-stable (ST) enterotoxin was confirmed. Secretory response against Escherichia coli heat-stable enterotoxin in this model was determined in terms of dilatation index (DI). DI equal to 0.50 or more was considered as a positive secretory response. Kinetics of fluid accumulation and the titration of toxin in guinea-pig ileal loop suggest uniform secretory response throughout the small intestine and 31.5 microgram of crude ST toxin as the minimum effective dose to induce a DI of 0.5. Guinea-pig intestine was found sensitive to both methanol soluble (STa) and methanol insoluble (STb) toxins of E. coli and so was considered superior to the existing suckling mouse assay (SMA), which is known to be sensitive only to STa toxin. In addition, GILA was also found to be more suitable and economical as at least 10 strains together with the positive and negative controls can be tested in one animal, whereas in SMA, four suckling mice were needed to test a single strain. Hence, in SMA individual susceptibility among mice cannot be ruled out. GILA was considered to be an alternative to the presently available test, SMA, in the determination of ST toxin of E. coli.

Animals↗

PubMed1991

Enterotoxin production & mouse virulence of clinical isolates of Salmonella typhimurium strains.

Twenty five isolates of S. typhimurium from clinical specimens were studied for markers of virulence. Three of five isolates from blood, both isolates from CSF and urine and only two of fifteen isolates from faeces were positive for fluid accumulation in rabbit ileal loop. All these strains produced an enterotoxic principle, antigenically related to cholera coli family of enterotoxins, as detected by latex agglutination and immuno-dot-blot tests. Polymyxin-B treated 6 h cultures yielded the best toxin. All 5 blood isolates, both CSF isolates and one of the two urine isolates showed low LD50 indicating high virulence. The study thus revealed that some strains of S. typhimurium are more virulent and produce more enterotoxins. These strains invade the intestinal mucosa potently and lead to extra-intestinal manifestations. The low virulent strains, on the other hand, are confined to the intestine and cause mild/moderate gastroenteritis. Enzyme assays were done in 5 representative strains of good, moderate and low toxin producers. Catalase and superoxide dismutase assays did not show any correlation with toxin production, thus suggesting that the enzyme production is unlikely to be a reliable indicator of the virulence for S. typhimurium.

Animals↗

PubMed1990

Characterization and genetic restriction of suppressor-effector cells induced by staphylococcal enterotoxin B.

The capacity of the staphylococcal enterotoxins to stimulate all T cells bearing certain (but not all) TCR has generated a great deal of interest. This stimulation appears to involve specific binding of the toxin to class II Ags and subsequent stimulation via the TCR. Previous studies from this laboratory have demonstrated that staphylococcal enterotoxin B (SEB) induces multiple T suppressor cell populations that inhibit both primary and secondary plaque-forming cell responses. Efforts to characterize these suppressor cell populations have demonstrated that the suppressor population active early in the antibody response expresses the Lyt-1-2+ cell surface phenotype, whereas depletion analysis suggests that the population active late in an ongoing response bears the Lyt-1+2+ cell-surface markers. In the present study, enrichment for this late acting effector population with the use of sequential panning with anti-Lyt mAb reveals significant suppressive activity at both the initiation and effector phases of a 5-day Mishell-Dutton coculture. Additional experiments using I-J disparate strains of mice have demonstrated a genetic restriction at the "I-J" gene locus between the cells mediating SEB-induced suppression and their target. Depletion of SEB-primed splenocytes with anti-I-J mAb suggests that both the early and late effector cells bear I-J molecules on their surface. Taken together, these results show that SEB induces suppressor cell populations with properties similar to those exhibited by Ag-specific cell circuits.

Animals↗

PubMed1991

Modified enterotoxin signal sequences increase secretion level of the recombinant human epidermal growth factor in Escherichia coli.

Amino acid substitutions were made in the heat-labile enterotoxin signal sequence of Escherichia coli by recombinant DNA techniques, and their influence on the secretion of recombinant human epidermal growth factor by E. coli was examined. The heat-labile enterotoxin signal sequence is an amino-terminal extension of the octadecapeptide chain and is comprised of three distinct regions: a positively charged amino-terminal region, a central hydrophobic region, and a carboxyl-terminal region with the cleavage site recognized by the signal peptidase. Some alterations in the signal sequence caused a 1.5-3.5-fold increase in the secretion of recombinant human epidermal growth factor. These were the introduction of: (i) polar and small residues into the carboxyl-terminal region (replacement of Pro-1 Leu-3 with Asn-Ala or Ser-Ala), which may give a favorable structure for the recognition and cleavage by the signal peptidase; and (ii) a polar residue into the central hydrophobic region (replacement of Ile-9 with Ser), which may cause an increase of the affinity to the cytoplasmic membrane. In the latter case, a large amount of the unprocessed "precursor" was accumulated. The combination of these modifications, however, did not work additively. An increase in the amino-terminal positive charge (insertion of Lys) had no effect on secretion. These results prove that the level of protein secretion is greatly dependent on the polarity of the carboxyl-terminal region and the hydrophobicity and/or the amphiphilicity of the central region. Moreover, the overall balance of the physicochemical properties of respective regions is important.

Amino Acid Sequence↗