Interrelationships between the virulence and the presence of M-protein in hemolytic streptococcus group A]

Experiments on mice demonstrated that of hemolytic streptococci A M types 2, 3, 12, 22, 46, and 49 characteristic is the absence of parallelism between their virulence for mice and the presence of M+-colonies in the microbial population. There was also a greater virulence for mice of M-variants. The established changes in serological properties of the cultures passaged in vitro were brought to the acquisition of polyagglutinability by the passage cultures, and to the loss of type-specific protection by the immune sera against these cultures. A possibility of acquisition by passage cultures of a factor determining their high virulence for mice, nonidentical to M-protein, is discussed.     

Monoclonal antibodies to different antigens of skin epithelium obtained by immunizing mice with streptococcus group A antigens

Monoclonal antibodies (MCA) were obtained by immunization of BALB/c mice with streptococcal group A protein antigens of the cellular wall, or with whole microbial cells. In immunofluorescence test, MCA react with different skin epithelial structures (basal, suprabasal or all the epidermal layers). The majority of MCA belong to autoantibodies. The same MCA revealed no cross-reactions with streptococcal antigens in immunoenzyme and inhibition tests. MCA reacting with epithelial cells are, apparently, obtained as a result of polyclonal activation of the autoreactive clones by streptococcal antigens.     

Regulation of virulence by a two-component system in group B streptococcus

Group B Streptococcus (GBS) is frequently carried in the gastrointestinal or genitourinary tract as a commensal organism, yet it has the potential to cause life-threatening infection in newborn infants, pregnant women, and individuals with chronic illness. Regulation of virulence factor expression may affect whether GBS behaves as an asymptomatic colonizer or an invasive pathogen, but little is known about how such factors are controlled in GBS. We now report the characterization of a GBS locus that encodes a two-component regulatory system similar to CsrRS (or CovRS) in Streptococcus pyogenes. Inactivation of csrR, encoding the putative response regulator, in two unrelated wild-type strains of GBS resulted in a marked increase in production of beta-hemolysin/cytolysin and a striking decrease in production of CAMP factor, an unrelated cytolytic toxin. Quantitative RNA hybridization experiments revealed that these two phenotypes were associated with a marked increase and decrease in expression of the corresponding genes, cylE and cfb, respectively. The CsrR mutant strains also displayed increased expression of scpB encoding C5a peptidase. Similar, but less marked, changes in gene expression were observed in CsrS (putative sensor component) mutants, evidence that CsrR and CsrS constitute a functional two-component system. Experimental infection studies in mice demonstrated reduced virulence of both CsrR and CsrS mutant strains relative to the wild type. Together, these results indicate that CsrRS regulates expression of multiple GBS virulence determinants and is likely to play an important role in GBS pathogenesis.     

The role of non-type-specific protein antigens of the cell wall in Streptococcus group A in developing delayed hypersensitivity

The role of the type-nonspecific (TNS) cell-wall antigens of group A streptococci has been determined. The study has been made on guinea pigs sensitized with whole microbial cells or HCl extracts containing TNS antigens. To determine delayed hypersensitivity, the in vitro cytotoxic test on adhering lymph-node cells in the autologous system has been used. The study has shown that sensitization with group A streptococci of different types or with TNS antigens induces the development of delayed hypersensitivity to TNS antigens (or antigen), common for different types of group A streptococci, but specific for this group. HCl extracts containing TNS antigens can be recommended as the preparation for testing delayed hypersensitivity to antigens, specific for group A streptococci.     

Relationship between the presence of K- and O-antigens and the behavior of salmonellae in a culture of macrophages]

It was shown on experimental models (mice and in kerato-conjunctival reaction) in comparative study of spontaneous stable salmonella mutants that disturbances in the process of synthesis of K- or O-antigens led to the weakening or the loss of the bacterial virulence. In the study of the behavior of the salmonella mutants it was revealed in the culture of phagocytizing macrophages that a reduction of the cytotoxic action of bacteria was connected with the changes of the somatic O-antigen, whereas the capacity of salmonella to reproduction inside the macrophages correlated with the presence of surface K-antigen.     

Relationship between the presence of microfilaments and the cell cycle of HeLa cells in synchronus culture]

Some cytoplasmic organelles have showed characteristic variations which are related to the different cell cycle phases, in thymidine synchonized HeLa cells in culture. In these cells, the most modified organelles were intracytoplasmic membranes (endoplasmic reticulum) and microfilament arrangements. Microfilaments were numerous under the cell membrane, but also some of them were dispersed in dense bundles. These structures were seen around the nucleus, 12-14 h after removal of excess thymidine (G1). They migrated to the periphery of the cell during S and G2. During mitosis, they were directly under superficial membrane-associated microfilaments.     

Variations in virulence between different electrophoretic types of Listeria monocytogenes

A total of 245 strains of Listeria monocytogenes, representing 33 different electrophoretic types (ETs), were examined quantitatively for haemolytic activity. No significant difference was observed in the mean haemolytic activity between different ETs. Eighty four out of 91 strains examined were found to be virulent for chick embryos. Strains belonging to ET 2 and ET 4 were found to be less virulent than strains of other ETs (P = 0.0447). Furthermore, strains from clinical cases were found to be more virulent (P = 0.0002) than strains from foods (the MTD among clinical strains was 2.46 in mean compared with 3.64 among food isolates). The explanation for this may be that more virulent strains are more prone to cause human infection. It is, however, also possible that strains of L. monocytogenes may become more virulent while multiplying in a living organism compared with multiplying in foods.     

Reactions of antibodies to streptococcus group A antigens with fibroblasts of human heart interstitial connective tissue]

The indirect immunofluorescence method was applied to the study of the serum of rabbits immunized with fractions containing nontype-specific antigens of streptococcus, group A, belonging to the cell wall proteins. Antibodies reacting with fibroblasts of the interstitial connective tissue of the human heart were revealed in the sera. On the basis of the experimental results of absorption a supposition was put forward on the presence of a cross-reacting antigen common with the fibroblast antigen in some hydrochloric extracts obtained from streptococci, groups A and C.     

The effect of immunization with Streptococcus group A on the development of delayed hypersensitivity to BCG antigens in mice of different strains]

Antibodies to group A streptococcal polysaccharide (A-PS) have been shown to appear within three weeks after the injection of group A streptococcus culture, heat-killed and treated with pepsin (A-STP), in the blood of not only BALB/c mice, but also CBA mice. As revealed in this study, in BALB/c mice antibodies are mainly active against the group-specific antigenic determinant (AD) of A-PS and in CBA mice, against the rhamnose AD of A-PS, common for streptococci of different groups. This study has revealed that the appearance of antibodies to the rhamnose AD of A-PS in the blood of CBA mice inhibits antigen-specific cytotoxicity, appearing with the development of delayed hypersensitivity to BCG antigens. This effect is not linked with the immunization of the animals with high doses of streptococci. Experiments have shown that the in vitro transfer of the inhibition of antigen-specific cytotoxicity to lymph node cells of normal BCG-sensitized animals may be carried out with lymph node cells of CBA mice, immunized with A-STP and having antibodies to the rhamnose AD of A-PS, but not with the serum containing these antibodies. The mechanisms of this effect are discussed.     

A screening for the presence of four different crystal protein gene types in 25 Bacillus thuringiensis strains

25 different strains of Bacillus thuringiensis, belonging to 18 different serotypes were screened by Southern hybridization analysis for the presence of nucleotide sequences of four different gene types coding for crystal proteins showing different insecticidal spectra. Many but not all strains showed sequences homologous to any of the probes used. Homology with sequences of the gene type present in strain kurstaki HD1 occurred in all positive strains, whereas the other gene types were much less abundant. Sequences homologous to those of gene type VI, coding for a Spodoptera-specific crystal protein, appeared only in strains of serotypes aizawai and entomocidus.