Studies on the hexose region of the lipopolysaccharide from a low virulence strain of Salmonella typhimurium.

The structure of the hexose region of the lipopolysaccharide from M206 strain, a mutant of Salmonella typhimurium having reduced virulence, was partially determined. Immunological tests indicated cross-reactions of anti-(M206) antiserum with wild-type C5 and Ra mutant strains. Data obtained on chemical composition, periodate oxidation, acetolysis, methylation and analysis by gas chromatography/mass spectrometry show that M206 type lipopolysaccharide contains the common core polysaccharide of Salmonella which was substituted in position 4 of the subterminal glucose unit by a disaccharide: D-glucosyl 1----3 D-galactose. This substitution is probably related to the slight virulence of M206 strain.

Influence of metabolic and physical factors on production of diacetoxyscirpenol by Fusarium sambucinum Fuckel.

Fusarium sambucinum Fuckel 8099-1 was grown on Czapek-Dox peptone-supplemented medium at 15 degrees C for 14 days, and the cultures were investigated for diacetoxyscirpenol (DAS) production by liquid-liquid extraction and gas chromatography. The addition of 150 mg of sorbic acid, a tricarboxylic acid cycle inhibitor, per liter stimulated both fungal growth and DAS production. Among the beta-hydroxy-beta-methylglutaryl coenzyme A precursors tested, isovaleric acid completely inhibited fungal growth and DAS production, ethyl isovalerate did not support a significant increase in DAS production, and L-leucine partially inhibited DAS production, showing that L-leucine and isovaleric acid catabolisms do not induce trichothecene biosynthesis. Solid particles (cork powder) were necessary for DAS production in stationary cultures but did not influence DAS production in shaken cultures. Shaking strongly stimulated DAS production and fungal growth.

[In vitro activity of an extract of Yersinia enterocolitica 0:3 biotype 4 on lymphoblastic transformation]. / Etude in vitro de l'activité d'un extrait de Yersinia enterocolitica 0:3 biotype 4 sur la transformation lymphoblastique.

Effects of an extract from Y. enterocolitica 0:3 biotype 4 on mouse splenocytes and human lymphocytes cultures were examined. Low doses had a mitogenic action on splenocytes, while high doses inhibited tritiated thymidine incorporation into the cells. With human lymphocytes only inhibitory effect was observed.

[Destruction and cutaneous decontamination of diacetoxyscirpenol (mycotoxin from the trichothecene group) by sodium hypochlorite]. / Destruction et décontamination cutanée du diacétoxyscirpénol (mycotoxine du groupe trichothécène) par l'hypochlorite de sodium.

Sodium hypochlorite was used to suppress diacetoxyscirpenol cutaneous toxicity; mice skin can be decontaminated with "Eau de Javel" (1 p. 100 free chlorine) if application is performed less than 15 min. after contact with toxin.

[Effect of temperature on diacetoxyscirpenol production and on sporulation in a liquid culture of Fusarium sambucinum]. / Influence de la température sur la production de diacétoxyscirpénol et sur la sporulation d'une culture liquide de Fusarium sambucinum.

F. sambucinum grown for 14 days on peptone supplemented Czapek medium produced higher amount of diacetoxyscirpenol at + 15 degrees C than at + 25 degrees C or at temperature kept successively at + 15 degrees C (day) and + 5 degrees C (night). There was no correlation between the spores number and the toxin level, but toxin synthesis began only with sporification and then continued until the 14th day.

[Experimental infection of mice by Salmonella typhi inoculated orally: influence of immunosuppressive therapy]. / Infection expérimentale de la Souris par Salmonella typhi inoculée par voie buccale: influence des traitements immunodépresseurs.

Various immunosuppressive treatments were used in order to induce a Salmonella typhi infection in mouse by oral route. Neither low protein diets nor administration of mucin, iron, streptomycin or silica could modify animal's sensitiveness, but, cyclophosphamide injections enhanced lethal effect of bacteria, while silica increased the number of bacteria in the blood and the spleen.

[Experimental cholera in monkeys]. / Etude du choléra expérimental chez le singe.

The immune response to Vibrio cholerae was studied in baboons, rhesus monkeys and marmosets inoculated by the oral, intraintestinal or intravenous route with various strains of V. cholerae. Sera were collected from all animals on days 2, 6, 10, 17, 24, 32, 45 and 60 after infection. Serum protein, immunoglobulins (IgA, IgG, IgM), GOT, and alkaline phosphatases were determined. The results showed that baboons and rhesus monkeys were not susceptible to cholera infection under these experimental conditions. However, we were able to induce a lethal cholera infection in cotton-topped marmosets. In baboons and rhesus monkeys serum IgG levels decreased significantly following inoculation with V. cholerae; however, the ratio of GOT, alkaline phosphatase and antibodies against toxin were only slightly modified.

[Evolution of mouse intestinal and blood immunoglobulins after oral route vaccination]. / Evolution des immunoglobulines intestinales et sériques de la souris après vaccination par voie orale.

The authors have studied the mice immunoglobulins level after vaccination by oral route with a killed-pathogenic strain of Salmonella typhimurium and an avirulent mutant of the same bacteria. The obtained results show an increase of the intestinal IgA and IgG1 levels and a slighter one of sera IgG between the 10 th and 30 th day following immunization. No correlation was observed concerning the IgM, IgG and IgA levels and the mice protection against a challenge of pathogenic bacteria.

Compared efficiency of a killed vaccine of Salmonella typhimurium, a live vaccine and an antigenic fraction in oral immunization of mice.

In an attempt to determine the best method of immunizing mice by oral route against Salmonella typhimurium, the animals were vaccinated by means of a killed-pathogenic strain, an avirulent mutant of the same bacteria, and a protective antigen removed from the supernatant culture of this mutant. After changing doses of vaccines and the interval between vaccination and challenge, the results obtained show the superiority of the live vaccine and protective antigen with regard to the killed one. Under our experimental conditions enteral vaccination appears to be more effective than the parenteral one.

[Protection by oral vaccination of mice with an avirulent live strain of Salmonella typhimurium]. / Etude de la protection de la Souris après vaccination par voie orale à l'aide d'une souche avirulenie vivante de Salmonella typhimurium

Before determining the quantity of mouse intestinal secretory IgA after oral vaccination, we have tried to find the best conditions of immunization with an avirulent S. typhimurium strain given by oral route. The results show the superiority of the live vaccin with respect to the heat-killed one.