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At least 955 records · Page 53Linked to original sources

PubMed1982

[Method of obtaining an erythrocyte diagnosticum for detecting Cl. perfringens type A enterotoxin].

Erythrocytic immunoglobulin diagnostic reagent for detecting Cl. perfringens enterotoxin in the indirect hemagglutination test has been obtained. The diagnostic reagent has been prepared on the basis of antibodies of Cl. perfringens enterotoxin with the use of acroleinized tanned sheep red blood cells. The indirect hemagglutination test with this reagent is characterized by high specificity and sensitivity (the method permits to detect enterotoxin protein at a concentration of up to 0.005 microgram/ml). The preparation thus obtained is stable and ensures highly reproducible results.

Animals↗

PubMed1983

High levels of heat labile Escherichia coli enterotoxin in bacterial cell sonicates of agar grown cultures.

Escherichia coli heat-labile enterotoxin from 5 strains of human and animal origin was detected in broth cultures and agar-plate culture sonicates by using CHO and Y-1 adrenal cells and rabbit intestinal loop assay. Cell sonicates possessed higher levels of heat-labile enterotoxin than supernatants of broth cultures. Highest levels of heat-labile (LT) enterotoxin were detected in the sonicates of cultures grown on blood agar, followed by those grown on MacConkey, and lactose agar respectively.

Agar↗

PubMed1984

Enterotoxin production by Yersinia enterocolitica in food samples.

Milk and cold meat samples were contaminated with 7 various serogroups of Yersinia enterocolitica strains. The infected food samples were incubated under different conditions of growth, at different temperatures and for different periods of time, then the number of colony forming units was determined and enterotoxin production was assayed by the suckling mice test. The Y. enterocolitica strains multiplied well under varying conditions of growth, but enterotoxin production could be detected only in the meat samples when incubated under shaking at 25 degrees C for 48 h. It may be assumed that performed yersinia enterotoxin is absent from food stored under normal conditions.

Animals↗

PubMed1983

[Presence of enterotoxin D in Staphylococcus aureus strains isolated from food products].

Studied was the capacity of 243 S. aureus strains to produce enterotoxin D after they were isolated from food products. It was found that 3.3 per cent of the strains produced enterotoxin D, the simultaneous production of A and D toxins being established in 2.5 per cent of the cases. The detection of an enterotoxin of such antigenic type pointed to its demonstration in cases of food intoxication as well as when hygiene control of food products was carried out.

Animals↗

PubMed1983

Pathogenicity tests with strains of Edwardsiella tarda: detection of a heat-stable enterotoxin.

A total of 25 strains of Edwardsiella tarda isolated from various sources in different parts of the world between 1968 and 1982 was subjected to enteropathogenicity tests. A heat-stable enterotoxin was detected in three strains (12%). Whereas culture filtrates gave doubtful results, concentration of toxin by ultrafiltration led to net fluid accumulation in the suckling mouse test and the rabbit ligated ileal loop assay. The enterotoxin resisted heating to 60 degrees C (30 min) and 100 degrees C (15 min). Neither cell elongation nor cytotoxic effect were observed in the Chinese hamster ovary cell assay. No strain caused keratoconjunctivitis in the guinea pig eye model. There was no correlation of enterotoxigenic strains and a typical pathology. With regard to the usual clinical pattern of E. tarda enteritis, which primarily appears to be invasive, it is suggested that enterotoxin production might be of secondary pathogenetical importance, comparable to toxin production in salmonellosis, shigellosis, and Yersinia enterocolitica infection.

Animals↗

PubMed1981

A simple procedure for isolation and purification of A-type staphylococcus enterotoxin.

A new procedure is presented for the isolation and purification of A-type staphylococcus enterotoxin. Homogeneous enterotoxin preparation was obtained by purification in 2 phases. In radial double agar-gel immunodiffusion the smallest precipitating dose of the isolated and purified enterotoxin was found to be 1.4-0.7 micrograms protein and 0.4-0.1 micrograms nitrogen. In cat experiments the dose giving a positive reaction was 2 micrograms protein or 0.5 micrograms nitrogen calculated for kg body weight.

Ammonium Sulfate↗

PubMed1980

[Infant mouse test for the assay of thermostable (ST) enterotoxin from Escherichia coli. Histological studies and influence of mice age (author's transl)].

Mices with different ages ranging 1 to 60 days old were inoculated with thermostable (ST) enterotoxin of Escherichia coli, either by intragastric injection through the abdominal wall or by intubation. Doses were proportional to body weight and values obtained for intestines/carcass weight ratios (RI/C) of inoculated mice showed that mice remained susceptible to the enterotoxin up to 16 days old, with RI/C values equal or greater than 0.085. Older mice were completely resistant to ST activity as RI/C values demonstrated. Histological observations showed that whole gut's fixation of inoculated mice was absolutely necessary since any handling of intestinal loops evoked artifactual alterations. Even though, alterations were found, probably of mechanical nature, caused by intestinal distension consequent to the increased fluid volume into gut's lumen. These alterations did not differ from those observed for both cholera and LT-E. coli enterotoxins, characterized by lymphatic and blood vascular dilatation within mucosae lamina propria, eventually shrinkage of lamna propria just below the epithelium as well epithelial's vacuolizations.

Age Factors↗

PubMed1980

Estimation of Vibrio cholerae and Escherichia coli heat-labile enterotoxin by enzyme-linked immunosorbent assay (ELISA).

By Enzyme-Linked Immunosorbent Assay (ELISA) purified cholera and Escherichia coli enterotoxins can be detected as sensitively as by CHO cells. There is a linear relationship between toxin concentrations and extinction values. In plates sensitized with toxins, antitoxins can be titrated with high sensitivity. ELISA cross-titration experiments demonstrate the existing antigenic relationship between cholera toxin and heat labile E. coli enterotoxin. Plates sensitized with either anti-E, coli-IgG or anti-cholera-IgG are suitable for detecting both cholera toxin, and E. coli LT. ELISA seems to be a simple, sensitive and economic method for quantitation of enterotoxins and toxin-specific antibodies.

Antigens, Bacterial↗

PubMed1980

Immunological cross-reactivity of heat-labile enterotoxins produced by enterotoxigenic and enteropathogenic strains of Escherichia coli.

Weanling rats were immunized with a heat-labile enterotoxin contained in whole cell lysate (WCL) ultrafiltrate preparations of enteropathogenic (EPEC) and enterotoxigenic (ETEC) strains or with a purified preparation of heat-labile toxin (LT) from the ETEC strain and then challenged either with viable bacteria of each strain or the purified ETEC LT by means of the ileal ligated loop technique. Immunization with the WCL toxin preparations of either the EPEC or ETEC strain conferred protection against challenge with viable organisms of both strains; immunization with a similar preparation from a nontoxigenic strain did not yield protection. Immunization with either the WCL or purified LT toxin from ETEC strain afforded protection against challenge with the ETEC LT toxin, but immunization with the EPEC WCL preparation did not. The antigenicity of all of the toxin preparations was destroyed by heat-treatment. Possible contributory protective effects of somatic or colonization factor (CFA) antigens present in the WCL were excluded by the findings that protection was afforded against a heterologous somatic serotype, ileal bacterial counts were not reduced in protected animals, and WCL preparations of strains containing or lacking CFA yielded equal protection. These observations indicate that the heat-labile enterotoxin of EPEC strains is antigenic and is immunologically related to a heat-labile toxin present in similarly prepared material from an ETEC strain but not to the conventional LT toxin of ETEC strains. They suggest that the WCL preparation of the ETEC strain contains two heat-labile enterotoxins, one of which is conventional LT and the other of which resembles the EPEC toxin.

Animals↗

PubMed1980

[Characteristics and function of enterotoxins of gram negative bacteria (author's transl)].

Several factors are important for the pathogenesis of bacterial intestinal disease: 1. Colonisation of the intestine; 2. exo(= entero)toxin production without penetration into the intestinal wall; 3. invasion of the intestinal wall with or without (?) simultaneous formation of enterotoxin. These factors are of different importance for the various infective agents. Whereas cholera is exclusively caused by an enterotoxin, this is of minor importance for the pathogenesis of Shigella dysentery. The enterotoxins of Vibrio cholerae, Escherichia coli, and Shigella dysenteriae 1 have been intensively studied. Additional enterotoxic substances have been demonstrated in other gramnegative organisms (Salmonella typhimurium, Yersinia enterocolitica, Klebsiella pneumoniae, Vibrio parahaemolyticus, Aeromonas hydrophila), which, however, are not yet characterized sufficiently. Future studies will aim to the elucidation of the structure and function of these toxins on the molecular level, and their importance for the pathogenesis of intestinal disease.

Aeromonas↗

PubMed1981

Genetic labeling of an Ent plasmid that encodes heat-stable enterotoxin of enterotoxigenic Escherichia coli isolated from patients.

Ent plasmids of enterotoxigenic Escherichia coli that encode heat-stable enterotoxin (ST) and both ST and heat-labile enterotoxin (LT) were labeled with a kanamycin- and an ampicillin-resistance transposon, respectively. These transposons were kept stably in the respective Ent plasmids. By monitoring antibiotic resistance we could easily select strains carrying Ent plasmids. Strains carrying the labeled plasmids produced enterotoxins that were immunologically indistinguishable from those produced by the parent strains. Moreover the strain carrying a labeled ST-Ent plasmid produced 16 times more ST than the parent strain.

Ampicillin↗

PubMedDate not supplied

[Identification of staphylococcal enterotoxins].

The important problem of the staphylococcal enterotoxins identification from cultures of Staphylococcus aureus and from foods is discussed in this work. The usefulness and reliability both of the media and methods for the enterotoxins production and of the techniques of identification are examined. For practical purposes is very important to use simple, sensitive, reliable and rapid methods for the identification of staphylococcal enterotoxins.

Enterotoxins↗

PubMedDate not supplied

[Correlation between the output of enterotoxins and heat-stable nuclease by Staphylococcus aureus strains isolated from various environmental matter].

Enterotoxins and thermostable DNase were found to occur concurrently in 94% of Staphylococcus aureus strains isolated during staphylococcal food intoxications. The presence of thermostable DNase in the absence of enterotoxin was detected in 45.6% of the strains isolated from food and in 28.8% of the strains isolated from the nasopharynx of clinically normal people undergoing scheduled examinations. Thermostable DNase was detectable more consistently than enterotoxin which seems likely to be produced only under special conditions. The presence in food of thermostable DNase alone, as revealed by sanitary and bacteriological examination, does not always suggest the presence of thermostable DNase is more closely associated with the staphylococcal strains which are isolated from the found in the food itself, giving rise to staphylococcal food intoxications.

Deoxyribonucleases↗

PubMed1981

A sandwich ELISA method for detection of Staphylococcus aureus enterotoxins.

Staphylococcus aureus enterotoxins A, B, and C, were detected by means of a four-layer sandwich ELISA method. With toxin produced in broth supernatants, this ELISA method had a detection limit of 0.5 ng enterotoxin per ml. Conjoint with enterotoxin, S. aureus most often produces protein A. The protein A will interfere and produce false positive reactions in a sandwich ELISA, by binding nonspecifically the IgG in different layers, simulating the immunospecific toxin binding. With rabbit IgG coupled to Sepharose CL-4B gel, 99% of protein A could be removed from solutions, bringing the level under the interfering limit in the ELISA.

Adsorption↗

PubMedDate not supplied

[Experimental study of enterotoxin type A persistence in canned goods].

Canned "Sprats in Oil" were infected experimentally with staphylococci which give rise to type A enterotoxin. It has been shown by the serological method that the enterotoxin localizes in the form of @nests" at sites of infection with staphylococci and their reproduction. Scientifically grounded sterilization regimes used nowadays in industry ensure complete inactivation in canned foods of staphylococcal enterotoxin, if any, before sterilization.

Animals↗

PubMed1980

Enterotoxin production of Yersinia enterocolitica strains.

Eighteen Yersinia enterocolitica serogroup O3, rhamnose negative strains isolated in Hungary from human enteritis, have been studied for enterotoxin production. Freshly isolated strains cultivated at 25 degrees C produced heat stable (ST) enterotoxin demonstrable in sucking mice, whereas strains isolated earlier and maintained in subculture lost their toxin producing capacity. No heat labile enterotoxin (LT) was found in the filtrate of the cultures or in their sonicated lysate. The ST of one strain exerted a dilating effect on the intestinal loop of rabbits. Strains cultured at 37 degrees C produced no toxin. Toxin production was demonstrable in Syncase medium but not in the modified Sakazaki medium. None of the strains caused keratoconjunctivitis; three strains elicited mild conjunctivitis in guinea pigs.

Culture Media↗

PubMed1994

Incidence of heat-labile enterotoxin-producing Escherichia coli detected by means of polymerase chain reaction amplification.

Diarrhoea can be caused by many different organisms, some of which are notoriously difficult to identify. One of these is enterotoxin-producing Escherichia coli. Recently a new diagnostic technique that uses polymerase chain reaction DNA amplification was developed for detection of the 'A' subunit of the labile enterotoxin-producing E. coli gene. This technique was used to evaluate the incidence of heat-labile (LT+) enterotoxin-producing E. coli in the causation of diarrhoea. The results from this study showed that LT+ E. coli is a cause of diarrhoea in the western Cape and that 5.3% of non-diagnosed diarrhoea patients in Tygerberg Hospital were infected with this pathogen. This represented less than 1% of the total number of cases of diarrhoea investigated in this hospital. The peak coincides with the wetter months in this locality and the infection rate is lower than that reported in most other countries. Given the low incidence of occurrence of this organism we do not recommend routine implementation of the diagnostic procedure. However, this test may be useful at times, e.g. to ascertain the source of a diarrhoea epidemic.

Adult↗

PubMed1993

Role of CD8 in staphylococcal enterotoxin B-mediated lysis by cytotoxic T lymphocytes.

Recent evidence has suggested that recognition of superantigens such as the staphylococcal enterotoxins by CTL occurs independently of the accessory molecule CD8. These conclusions are based on the observation that antibodies to CD8 do not appear to be effective inhibitors of T cell lysis that is mediated by enterotoxin. This is in contrast to the well-known inhibitory effects of anti-CD8 antibodies on T cell activation by most peptide/class I complexes. In this study, we show that lysis of staphylococcus enterotoxin B (SEB)-bearing target cells by the mouse alloreactive CTL clone 2C is inhibited by anti-CD8 antibodies. SEB-mediated lysis by a polyclonal population of mouse CTL was also inhibited by anti-CD8 antibodies, but only under conditions where the SEB concentration is low. Inhibition occurs even when class I negative Daudi cells are used as targets. Thus, the observed inhibition does not appear to be due to the prevention of intercellular interactions between CD8 and class I molecules but is probably a consequence of preventing the intracellular association of CD8 and TCR. At the high ligand densities used in most previous studies, very few of the CD8/TCR complexes may be required for activation. Under these conditions, lysis may appear to be CD8 "independent" because 1) there are a sufficient number of preexisting CD8/TCR complexes for activation; or 2) prohibitively high concentrations of antibody would be needed to saturate unassociated CD8.

Animals↗