Enterotoxigenicity of Salmonella strains of various origins

The study of the enterotoxigenicity of S. typhimurium with the use of the skin test on rabbits (to detect the delayed permeability factor) has revealed that these strains produce an enterotoxin similar to Escherichia coli thermolabile enterotoxin (TLE). Study of the enterotoxic activity of lysates obtained from 39 S. typhimurium strains and 5 S. dublin strains by sonication has revealed that 87% of S. typhimurium strains and all S. dublin strains produce an enterotoxin similar to E. coli TLE, as demonstrated by all tests used in this investigation, while 59% of S. typhimurium cultures and all S. dublin strains have been positive when tested for the capacity of producing the rapid permeability factor. "Hospital" strains and polyresistant cultures isolated from the environment (phagovar 20) are characterized by a higher rate of producing an enterotoxin similar to E. coli TLE, detected by the tests used in this investigation (90%), than antibiotic-sensitive strains of different origin (78%).     

The enterotoxigenic capacity of hemolysin-producing strains of Proteus isolated in acute intestinal infections in children

The capacity of P. mirabilis and P. vulgaris strains isolated in acute enteric infections in children for producing enterohemolysin, a new type of hemolysin, has been shown. The relationship between the capacity of Proteus cultures for producing enterohemolysin and their capacity for inducing toxic secretory reaction on a ligated loop on the small intestine of rabbits in the absence of known thermostable and thermolabile antitoxin in bacteria.     

Trial of different nutrient media for the production of an intracellular thermolabile enterotoxin by Escherichia coli strains H74-114 and 86

The conditions of cultivation, ensuring the maximum accumulation of intracellular thermolabile enterotoxin in the cultures of two E. coli strains of different origin, have been studied. Culture media manufactured in the USSR have been selected and the conditions of cultivation, necessary for obtaining intracellular thermolabile enterotoxin in preparative amounts, have been established. Under these conditions the yield of thermolabile enterotoxin in 1.4 mg per 1 liter of culture medium for strain H74-114 and 1.0 mg per 1 liter of culture medium for strain 86.     

Antibiotic sensitivity and pathogenetic factors of hospital strains of Pseudomonas aeruginosa isolated from patients treated in a resuscitation unit]

Strains of Pseudomonas aeruginosa were isolated from patients treated in the Centre of Thermal Affections in 1985-1989. It was shown that 72.9, 59.3, 33.8 and 54.2 per cent of the isolates were sensitive to cefotaxime, tobramycin, gentamicin and polymyxin, respectively. The study of pathogenicity factors of the isolates revealed that 83 per cent of the strains produced thermolabile enterotoxin, 79.6 per cent of the strains had adhesive activity and 71.1 per cent of the strains produced hemolysin. The study detected combinations of various pathogenicity factors. 42.3 per cent of the isolates had both adhesive and enterotoxigenic properties. Adhesiveness and hemolytic activity were shown by 13.5 per cent of the strains. 16.9 per cent of the strains produced both enterotoxin and hemolysin. Adhesive activity, enterotoxigenicity and hemolysin production were observed in 6.7 per cent of the strains. It was noted that the strains of P. aeruginosa resistant to polymyxin mainly produced enterotoxin (18.6 per cent) and those resistant to cefotaxime had adhesive activity (34.0 per cent).     

Modification of a method of passive immune hemolysis on a solid medium for detecting the production of thermolabile enterotoxins by Vibrio cholerae and Escherichia coli strains

A modification of the passive immune hemolysis method for the determination of the production of thermolabile enterotoxins by V. cholerae and E. coli is proposed. This modification permits the use of solid culture media. Experiments with cholera enterotoxin have demonstrated that the sensitivity of the modified method is 8-10 times higher than that of the Elek method. Similar results have been obtained with the use of the proposed method in the study of the capacity of different V. cholerae and E. coli strains for producing enterotoxins. The results obtained with the use of this method have been found to correlate with those obtained by means of the skin test and passive immune hemolysis in a liquid medium. We have used the modified method in the study of the production of thermolabile enterotoxin in transconjugants obtained by the hybridization of E. coli strain GA 107 carrying plasmid pCG86 which determines the synthesis of thermolabile and thermostable enterotoxins and E. coli strain K12 C600 R. The results obtained in the study of toxin formation in 99 transconjugants, carried out with the use of the proposed method, the skin test and passive immune hemolysis, have been shown to coincide.     

Production of cytotoxin VT in enteropathogenic and non-enteropathogenic Eschericha coli strains of porcine origin

Abstract We have investigated the production of verotoxin (VT) in 55 enteropathogenic and 48 non-enteropathogenic Escherichia coli strains of porcine origin, belonging to 48 serotypes. VT cytotoxin was only produced by seven out of the eight enteropathogenic strains with serotypes O138:K81, O139:K82, O141:K85ab and O141:K85ac. Five haemolytic non-enteropathogenic E. coli , four with serotypes O75:K-, O75:K95 and O2:K2, and one not typable, synthesized a new thermolabile product not related with enterotoxin (LT) or VT, and which induced the formation of multinucleate cells in Vero monolayers.     

Comparison of a competitive enzyme immunoassay kit and the infant mouse assay for detecting Escherichia coli heat-stable enterotoxin

A commercial competitive enzyme immunoassay kit, Escherichia coli ST EIA, was compared with the conventional infant mouse assay for sensitivity and specificity in detecting E. coli heat-stable enterotoxin. Thirty-one of 46 strains of E. coli tested were positive by both assays, while 15 strains were negative. The sensitivity of the ST EIA kit was up to 64-fold lower than the infant mouse assay.     

Detection of enterotoxic strains of Escherichia coli in children with diarrhea treated at the Child Health Center 1986-1988

Studies on detection of enterotoxigenic strains of E. coli were carried in 1986-1988. During this time 2324 rectal swabs from children with diarrhoea symptoms were tested. On the whole 701 E. coli were selected. The ability to produce thermolabile enterotoxin by E. coli strains was evaluated by three methods: Elek test, passive immunohemolysis and ELISA. Among selected E. coli strains enterotoxigenic strains accounted for 21.8% in 1986, 16.3% in 1987 and 28.2% in 1988.     

Interrelation of the enterotoxigenic properties and the antigenic structure of Escherichia

The enzymatic signs and serological characteristics of Escherichia enterotoxigenic strains isolated from patients with acute intestinal diseases and from healthy persons were studied. The cultures were subdivided into 24 enzymatic variants and classified with 48 serogroups and 61 serovars. The enterotoxigenic properties of the strains were compared with their serological characteristics and enzymatic signs. The strains, isolated from different persons and classified with the same serovar, belonged to the same variant with respect to the type of enterotoxin they produced (only thermostable enterotoxin, only thermolabile enterotoxin, or both), were similar in the degree of their toxigenicity and belonged, as a rule, to the same enzymatic variant. The data on the presence of manifest interrelation between the enteropathogenicity of Escherichia and their structure, as well as on the stability of the enterotoxigenic properties of these organisms, indicate that in acute intestinal diseases the determination of Escherichia enterotoxigenic strains can be carried out by common bacteriological techniques with the use of specific agglutinating sera.     

Enterotoxigenic Escherichia in patients with acute intestinal infection

Out of 4,082 Escherichia strains isolated from 989 hospitalized patients with acute enteric infections 2,979 strains belonged to 139 O-groups and the remaining strains could not by typed with O-sera (O1-O164) or were in the serological R-form. 19.3% of the strains isolated from 354 patients showed a positive reaction for thermolabile enterotoxin (TLET) determined in the radioimmunoassay. Escherichia with pronounced reaction for TLET were isolated from 5.5% of the patients. The serological picture of Escherichia with a positive reaction for TLET comprised 78 O-groups, showed practically no variations in children of different age and adult patients and was related to the intensity of reaction for TLET. The number of enterotoxigenic Escherichia greatly varied within individual O-groups: from 3.1 +/- 3.63% (O11) to 100 +/- 9.81% (O114) of the total number of known strains in these O-groups. In most O-groups the number of enterotoxigenic strains varied from 10% to 50%. The most widely spread serovars of etiologically important enterotoxigenic Escherichia belonged to 24 O-groups and were often isolated as monocultures. The capacity for producing TLET (and, probably, some other antigenically related substances) in widely spread among Escherichia; still, the determination of enterotoxicity is a necessary, but not sufficient criterion of their etiological importance in acute enteric infections.     

Characteristics of the B subunit of a thermolabile Escherichia coli enterotoxin produced by the A-B+ E. coli strain

The preparation and identification of B subunit of thermolabile enterotoxin produced by A-B+ gene-containing strain are described. The E. coli strain studied is shown to produce protein identical in its molecular properties and antigenic specificity to B subunit obtained from the whole thermolabile enterotoxin. Partial antigenic affinity between B subunits of thermolabile enterotoxin obtained from different sources and B subunit from cholera enterotoxin has been established in immunochemical studies. Electrophoretic and immunochemical analysis has confirmed the absence of A-subunit admixtures in B-subunit preparation obtained from /A-B+/E. coli strain.     

Production of cholera-like enterotoxin by Aeromonas hydrophila

A total of 249 strains of mesophilic Aeromonas including 179 A. hydrophila and 70 A. caviae were tested for production of cholera-like enterotoxin by reversed passive latex agglutination (RPLA) assay. A cholera-like enterotoxin neutralized with cholera antitoxin was demonstrated in the culture filtrates from eight (4.5%) of the 179 A. hydrophila strains, while none of A. caviae strains revealed the enterotoxin production in the test. Production of the cholera-like enterotoxin in the eight strains of A. hydrophila was also confirmed by enzyme-linked immunosorbent assay (ELISA).     

State of several parts of immune system in mice, infected by enterotoxigenic bacteria of Enterobacter genus

Influence of thermolabile enterotoxin bacteria of Enterobacter genus on the immune system of mice was studied. Assessment of phagocytic functions of the immune system as well as antigen-presenting functions of macrophages during infection with enterotoxin-producing strains of bacteria from Enterobacter genus revealed pleiotropic effect of the toxin which is characterized by inhibition of antigen-presenting and processing functions of macrophages.     

Dynamics of biologically active enterotoxin release by E. coli]

Accumulation of E. coli enterotoxin in the Finkelshtein's culture medium in growing the cells in a 30-litre reactor was studied. Accumulation of active highly molecular enterotoxin occurred in the course of a 6-hour cultivation of E. coli, strain P-99 (O141: K85ab; K88ab: H4) in the fluid medium under aeration. Oxygen utilization, synthesis and release into the nutrient medium of pyruvic acid, and protein accumulation were observed. The preparation obtained was stable to the lyophylic drying, contained thermolabile and thermostable toxins and marked edema of mouse limbs. The data obtained were of significance for the industrial production of active enterotoxin preparations.     

Escherichia coli isolated from seafood: toxicity and plasmid profiles

Thirty-two Escherichia coli strains were isolated from red snapper (Lutjanus purpureus) and from seabob shrimp (Xiphopenaeus kroyeri). The strains were numbered S1–S16, and F1–F16, which corresponds to the isolation origin from shrimp (S) and fish (F). The isolates were biologically and antigenically characterized by agglutination tests with enteropathogenic E. coli (EPEC)-, enteroinvasive E. coli (EIEC)- and enterohemorrhagic E. coli (EHEC) O157-specific antisera. The ETEC enterotoxins were characterized by GMI-ELISA for enterotoxin LT-1 (thermolabile) and by inoculation of supernatants prepared from newly born mice for enterotoxin Sta. A total of 14 strains produced exotoxins, of which seven were thermolabile (LT) and seven were thermostable (ST). Antimicrobial susceptibility profiles were determined by disc diffusion in agar using ampicillin, cephalothin, cefoxitin, ceftriaxone, imipenem, nalidixic acid, ciprofloxacin, chloramphenicol, gentamicin, nitrofurantoin, sulfamethoxazole–trimethoprim, and tetracycline. Four isolates showed lower susceptibility to some antibiotics, two strains were resistant to ampicillin, tetracycline, and sulfamethoxazole-trimethoprim, and two were resistant to tetracycline and nitrofurantoin. Plasmids were extracted in the four resistant isolates; two of them contained plasmids whose molecular weight varied from low to high. The characterization of LT- and ST-toxin-producing E. coli strains displaying multiresistance and containing plasmids suggests the need for tightening current control measures for the use of antimicrobials. Electronic Publication     

Production of enterotoxins by strains of Escherichia coli isolated from pigs

The production of enterotoxins by 237 hemolytic strains of Escherichia coli isolated from pigs was determined with the use of CTE in CHO. Vero and Hela cells and ILT. More frequent (p less than 0.01) production of enterotoxins, determined by ILT, was found for the serotypes being pathogenic for the animals (63.8% of the strains). No correlation between intensity of ILT and particular serotype was observed. Both the serotypes pathogenic for pigs and other serotypes produced LT enterotoxins and ST toxin. The frequency of LT enterotoxin production was statistically insignificant compared to the frequency of ST enterotoxin production by strains with serotypes pathogenic for the pigs. Strains of E. coli producing only enterotoxin ST belonged both to the pathogenic serotypes as well as to other hemolytic serotypes. The cytotoxic activity of supernatants of E. coli strains with different serotypes isolated from pigs in Vero and Hela cells and simultaneous CTE in CHO cells was observed. This suggests the production by the strains of enterotoxin LT and cytotoxin VT. Seven out of the 96 isolates showing CTE in CHO cells gave no reaction in the ILT in pigs. This suggests the production by these isolates of a toxin (toxins) differing from the E. coli enterotoxins.     

Vero cytotoxin production and HeLa cell adherence of enteropathogenic Escherichia coli of infantile diarrhoea in Iran

A total of 70 enteropathogenic Escherichia coli (EPEC) strains belonging to 11 serogroups, isolated from infantile diarrhoea in Tehran, Iran, were tested for the production of verocytotoxin (VT), enterotoxin, and also for their adherence to HeLa cells. In total 55 (78.5%) strains were either VT (32 strains) or enterotoxin (23 strains) producers, and of these 8 strains produced both VT and enterotoxins. 57 (81.4%) strains showed either Localized (LA) or Diffuse adherence (DA) or both types of adhesion (LA/DA) on HeLa cells, with strains showing LA/DA in the same preparations being dominant (32 strains), followed by those showing LA (14 strains) and DA (11 strains). Among adherent EPEC, 26 (37.1%) strains belonging to the serogroups 020, 086, 0119, 0125, 0126, 0127 and 0128 also produced VT. These findings suggest that production of VT and enterotoxin is an important factor in the pathogenesis of EPEC diarrhoea in Iran and that the combination of adherence and production of toxins is a common feature of EPEC strains which cause diarrhoea in this country.     

Enzyme immunoassay system for detection of staphylococcal enterotoxin,type C

An enzyme immunoassay (EIA) system for detection of staphylococcal enterotoxin, type C, has been developed. The sensitivity of the system is 1 ng/ml. The optimum EIA parameters have been worked out. The absence of false positive results with heterologous toxins confirms the specificity of the assay system. The possibility of the detection of staphylococcal enterotoxin, type C, in staphylococci isolated from different sources has been shown.     

Immunofluorescent Detection of Enterotoxin B in Food and a Culture Medium

Both Staphylococcus aureus strains 243 and S-6 cells producing enterotoxin B and free enterotoxin in food and culture medium were rapidly demonstrated by using the fluorescent-antibody technique. Comparison of cell fluorescence and enterotoxin B production determined by double gel diffusion showed that an estimation of enterotoxin production could be made by observing the degree of cell fluorescence. The fluorescent-antibody technique was used to determine whether cells were producing enterotoxin under varying nutritional and environmental conditions: NaCl concentration, culture aeration, and time and temperature of incubation in Brain Heart Infusion broth and shrimp slurries. At the various NaCl concentrations, the fluorescence of cells was found positively associated with enterotoxin B production only during the first 12 hr of growth. As the NaCl concentration was increased from 0 to 10%, the fluorescence of cells and toxin production decreased. Maximum for cell fluorescence and enterotoxin production was observed at 37 C. Little or no difference in cell fluorescence and enterotoxin production with both strains was found between Brain Heart Infusion broth and shrimp slurry cultures. All results obtained with the fluorescent-antibody technique were verified with double gel diffusion for enterotoxin detection and quantitation.     

Variation in the behaviour of enterotoxigenic Staphylococcus aureus after heat stress in milk

The survival of several strains of Staphylococcus aureus after heat stress in different menstrua was not logarithmic and F-values were determined to express their resistance to heat. Of the strains tested, Staph. aureus 234 (enterotoxin B) was the most heat resistant and Staph. aureus 790 (enterotoxin E) was the most heat sensitive. Buffalo milk gave the best protection to all the strains of Staph. aureus against heat, followed by cow's milk; phosphate-buffered saline gave the least protection. Soyabean casein digest agar gave maximum recovery of survivors followed by brain heart infusion and Baird-Parker medium. At 50 degrees C there was no marked variation in coagulase production by the surviving strains but at 55 and 62.5 degrees C there was complete loss of coagulase activity. There was a decreased deoxyribonuclease (DNase) production by all the strains of Staph. aureus after heat stress. Heat-treatment at 55 and 62.5 degrees C resulted in loss of enterotoxin production by all the survivors except S6 and 234, the surviving cells of which still produced enterotoxin B after heat treatment at 55 degrees C. Most of the survivors regained lost characteristics such as coagulase, DNase and enterotoxin production after four to five passages through BHI which suggests that subculture of Staph. aureus recovered from heat-processed milk is necessary to avoid false results.