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S Schlecht

Publications and source records attributed to S Schlecht.

11 recordsLinked to original sources
PubMed1979

[Protective role of Salmonella R mutants in Salmonella infection in mice (author's transl)].

NMRI mice were immunized with acetone-killed bacteria of 6 salmonella R mutants, 5 homologous and 6 heterologous Salmonella S forms and 3 E. coli R mutants. The animals were then challenged with graded amounts of live S. typhimurium. The results show that the protection obtained was dependent on the number of immunizing injections and on the time interval between them. Thus in the case of Salmonella R-mutants two immunizations increased the LD50 of challenge by an index of two (log 10) compaired to one immunization. A third immunization led to only a small further increase, the protection however, was longer lasting. A 3 fold immunization with two Salmonella typhimurium mutants, one SR- and one Ra form, led to a protection comparable to that obtained with S form bacteria. In contrast to the R-mutants, with Salmonella typhimurium S form a high degree of long-lasting protection was achieved already after a single immunization, and was not increased significantly by repeated injections. In animals immunized with Salmonella typhimurium S form the difference between non-lethal and 100% lethal challenge dose varied by a factor of 10 (one injection dose). In contrast, in animals immunized with Salmonella R mutants the above differences were more gradual extending over 3, 4 or more infection doses. This was also true for animals immunized with lower doses of S. typhimurium S form and for the non-immunized control animals. For comparison the protective effect of heterologous Salmonella S forms and of E. coli R-mutants was studied. These were found to be less effective in affording protection to Salmonella typhimurium than the above Salmonella R forms. The various strains used for immunization may be placed in the following sequence in order of decreasing protection: Salmonella typhimurium S form, Salmonella R-mutants, heterologous Salmonella S forms, E. coli R mutants. In a parallel investigation the antibody inducing properties of Salmonella R mutants and heterologous Salmonella S forms were studied. In all cases homologous hemaglutinating antibodies to all the strains used for immunization were detectable. In immunization with Salmonella R mutants in addition to homologous titres, agglutinating antibodies to Salmonella typhimurium S form were also produced in significant amounts. There was, however, no correlation between the time of appearance of protection and that of appearance of antibodies nor between the hight of antibody titres and degree of protection. The detection of agglutinins to the infecting microorganisms represents therefore no valid criterium for the effectiveness of R mutants and heterologous Salmonella S forms as protective vaccines. From the present results it is concluded that in addition to the O antigen one or more further cell components exist which are involved in rendering animals immune to Salmonella typhimurium and probably also to other Salmonella S form bacteria.

Agglutination Tests↗
PubMed1976

Antigenic determinants of murein lipoprotein and its exposure at the surface of Enterobacteriaceae.

Murein lipoprotein from the outer membrane of Escherichia coli could be fixed to erythrocytes without pretreatment of the erythrocytes. Passive hemagglutination or immune hemolysis could thus be used as sensitive assays to determine antibodies against lipoprotein. In rabbit antisera prepared against whole cells of E. coli, Salmonella, Arizona, and Shigella antibodies against lipoprotein were present. The respective titers were lowest in encapsulated smooth strains and highest in rough mutants. Antisera against deep rough mutants showed even higher anti-lipoprotein titers than anti-R-lipopolysaccharide titers. Correspondingly,absorption of lipoprotein antibodies with enterobacterial strains was most pronounced with deep rough mutants and lowest with smooth strains. Lipoprotein becomes increasingly an immunogen as well as an antigen the more sugar residues are missing in the lipolysaccharide on the cell surface. In wild-type cells lipoprotein is buried in the outer membrane; its exposure in mutant cells is related to defects at the cell surface.

Animals↗
PubMed1976

[Demonstration of antibodies to salmonella-R-antigens in sera of patients suffering from salmonelloses (author's transl)].

The extent of hemagglutinating antibody titers against Salmonella R-lipopolysaccharides in 189 sera of 119 human beings suffering from various salmonelloses was estimated. When compared to serum specimens of 137 healthy persons a significant rise in the number of Ra- and Rb2-titer containing sera was observed. It was further found that titers directed against chemotypes Ra, Rb2 and Rc were significantly enhanced in height when compared to the control group. Sera of healthy persons and patients did not show significant differences in Rd1-, Rd2- and Re-titers, respecively. The results indicate that the innermost part of the LPS core in Salmonella S-forms is considerably less (or even none) immunogenic in respect to antibody formation. R-titers in sera from patients suffering from salmonelloses as well as from healthy persons were predominantly directed against Ra-, Rb2- or Rc-LPS structures; the Ra-titer being the most frequent one in both groups. More detailed analyses on sera from patients suffering from salmonelloses revealed a somewhat lower content of R-titers in the early stage of infection. Furthermore in typhoid fever changes in the height of Ra-titers paralled the usual course of O-titers and in gastroenteritic infections the course of illness, respectively. The immunogenicity of the LPS core, however, was less expressed than that of the O-polysaccharides as revealed from a comparison in extent and height of R- and O-titers. Frequently the salmonelloses sera showed titers against several R-antigens. In such cases Ra-titers mostly occurred either together with Rb2-titers alone or concomitantly with both Rb2- and Rc-titers. In absorption experiments it could be demonstrated that two types of antibodies had been formed, those directed against terminal sugar residues in R-lipopolysaccharides and others with specificties against internal partial structures of the core.

Antibodies, Bacterial↗
PubMed1975

Immunological responses to Salmonella R antigens. The bacterial cell and the protein edestin as carriers for R oligosaccharide determinants.

Responses in rabbits to heat-killed Salmonella minnesota R mutants (chemotypes Ra, Rc and Re) were heterogeneous with respect to the amounts and specific haemagglutinin activities (SHAA) of IgM and IgG antibodies produced to each mutant. Amounts of antibodies in IgM and IgG fractions of sera were determined by quantitative precipitation. For comparison, antibodies were also isolated using an R oligosaccharide-specific immunoadsorbent and quantitated spectrophotometrically. SHAA (haemagglutinating units/mg antibody) of IgG antibodies were similar for all three mutants. In contrast, the Ra mutant induced IgM antibodies with the highest SHAA, while the Re mutant induced IgM antibodies 10-fold lower in activity. The ratio of the amount of IgM/IgG produced was approximately 1/1 for both the Ra and the Rc mutants, while the ratio for the Re mutant was about 1/2. Salmonella R oligosaccharide-protein conjugates (chemotypes Rb2, Rc and Re) were prepared, and the responses to these antigens were compared with those to the heat-killed mutants. The conjugates were specific for the given chemotype, and they were strongly immunogenic when incorporated into Freund's complete adjuvant and administered intramuscularly. Haemagglutinin titres were relatively high, but amounts of antibodies were considerably reduced when the conjugates were administered intravenously without adjuvant. Rabbits immunized with the conjugates in the same manner as with heat-killed R mutants produced predominantly IgM responses in all three cases.

Adsorption↗
PubMed1975

[Growth and lipopolysaccharide content of salmonellae grown in submersed cultures according to the batch-method. 2. Communication: influence of growth phases on lipopolysaccharide synthesis (author's transl)].

The paper describes cultivations of 4 Salmonella S-forms and 1 SR mutant, performed in complex medium under constant conditions of temperature, pH and aeration. The experiments show that lipopolysaccharide (LPS) biosynthesis underlies quantitative differences with the growth phases, resulting in changes in the LPS content of the cell masses. During the exponential phase a decline takes place in the percentage of LPS contained by the 4 S-forms. In addition, in the phase of delayed growth acceleration, 3 of these strains exhibit temporary, complete stagnation in LPS formation. When the cultures enter the stationary phase, LPS biosynthesis also discontinues. The SR-mutant differs from the S-forms especially in that the rate of LPS synthesis and with it, the percent lipopolysaccharide content of the cells, increase greatly in the exponential growth phase. The causes and effects of the changes observed are discussed.

Cell Division↗
PubMed1975

[Chemical and serological characterization of Salmonella lipopolysaccharides from different phases of growth (author's transl)].

Chemical and serological investigations were carried out on lipopolysaccharides of 4 Salmonella S-forms and of 1 SR-mutant, extracted from bacteria at different ages of culture (early exponential to stationary growth phase). The results show that the fatty acid composition of Lipid A (lauric-, myristic-, palmitic-, and beta-hydroxy-myristic acids) does not undergo any significant change during the growth of the cultures. However, there are differences in the molar ratios of the fatty acids from strain to strain. In all phases of growth Lipid A is substituted by basaloligosaccharide, to the same extent, as can be seen from the constant ratios of beta-hydroxy-myristic acid: heptose. Serological experiments (haemagglutination inhibition tests, absorption of antibodies by LPS-coated erythrocytes) showed that in no case the basaloligosaccharide is completely substituted by O-specific chains and that basaloligosaccharide exhibits free R-antigen structures which are mainly of chemotypes Ra, Rb and Rc, for the SR-mutant only of types Ra and Rb. There is no demonstrable dependence upon the phases of growth. In the O-specific polysaccharide chains the sugars of the main chain and the side bound dideoxy sugars (abequose and tyvelose) show a constant 1:1 molar ratio in all phases. In the case of S. typhimurium, antigen factors 1, 4 and 12(2), the biosynthesis of which is controlled by modifying oaf genes and/or by a lysogenic phage, are of a somewhat weaker expression in the exponential phase than in the latter phases of growth. In the SR-mutant, lipopolysaccarides with (low) serological O1 and O12(2) activity are only extractable by the phenol/water method, but not by the PCP method. In three out of four S-forms, changes occur in the length of the O-specific polysaccharide chains, whereas the number of repeating units of the fourth strain remains almost unchanged. The lipopolysaccharides of the SR-mutant contain in all phases of growth about one repeating unit. In all strains the covering of the cell surface by lipopolysaccharide molecules changes during the course of growth, as can be seen by comparing the relative cell surface and the content of Lipid A fatty acids of the bacteria. Lipid A synthesis in the 4 S-forms is reduced in the exponential phase and/or in the phase of delayed growth acceleration. The extent of biosynthesis of the carbohydrate moiety of lipopolysaccharides is independent of that of Lipoid A. In the SR-mutant, Lipoid A and Polysaccharide are formed in increased amounts in the exponential growth phase.

Cell Wall↗
PubMed1975

Reactivity of lipopolysaccharides from various salmonella SR and R chemotypes Ra-Re mutants with concanavalin A.

Lipopolysaccharides from different R mutants of Salmonella minnesota and Salmonella typhimurium belonging to chemotypes Ra to Re, as well as from three SR mutants of Salmonella typhimurium were selected for a study of their precipitability with Concanavalin A. Predictions as to the outcome of the reaction could be made since both the chemical structure of the Salmonella R lipopolysaccharides and structural requirements for a positive reaction with Concanavalin A are well established. Precipitation studies in the immuno-electrophoretic assay and in the microcapillary test were carried out with alkali-treated lipopolysaccharides as untreated lipopolysaccharide is too highly aggregated to allow a sufficient migration in agarose layers. Lipopolysaccharides of all mutants--except the SR mutants--were obtained by the phenol/chloroform/petroleum ether method in order to avoid contaminations by glucans or glycogen which are known to occur in phenol/water extracted lipopolysaccharides and which would lead to erroneous results. Additional precipitation studies were carried out with two other lectins of different polysaccharide specificity: Wheat Germ Agglutinin and Soybean Agglutinin. As expected, lipopolysaccharides of chemotypes Ra, Rb1, and RcP- mutants reacted strongly with Concanavalin A, whereas no reaction was demonstrable with lipopolysaccharides of chemotypes Rb2, Rb3, Rd and Re mutants. The lipopolysaccharide of an RcP+ mutant unexpectedly failed to precipitate unless it was dephosphorylated with HF. This artificially prepared RcP-lipopolysaccharide showed a strong reaction, thus demonstrating that negative charges in the direct neighborhood of reactive sugar units as in RcP+ LPS may prevent precipitation with Concanavalin A. No reactivity demonstrable by precipitation could be obtained using either Wheat Germ Agglutinin or Soybean Agglutinin with alkali-treated lipopolysaccharide even of those chemotypes which had the supposedly reactive sugar in a terminal position, such as N-acetyl-D-glucosamine in Ra mutants (Wheat Germ Agglutinin) or D-galactose in Rb2 or Rb3 mutants (Soybean Agglutinin).

Acetylgalactosamine↗