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Biomedical subjects

K B Grabovskaia

Publications and source records attributed to K B Grabovskaia.

At least 19 recordsLinked to original sources
PubMed1990

[Preparation of immune sera to group A streptococcus lipoteichoic acid].

A method is described for the preparation of sera highly active in reactions with Group A Streptococcus lipoteichoic acid. Ultrasound-destroyed biomass of Streptomyces levoris K-3053 strain is used as the antigen. This strain was isolated in studies of soil Streptomyces; it contains sufficient amounts of nonglycosylated glycerolteichoic acid of the first-third types, that is identical in structure to polyglycerophosphate skeleton of Group A Streptococcus lipoteichoic acid.

Immune Sera↗
PubMed1990

[Group B streptococci in neonatal pathology: pathogenetic mechanism, diagnosis and prevention].

Group B streptococci have recently attracted the attention of researchers as the causative agents of human neonatal disease. They are currently encountered much more frequently than it was believed previously. Various types of adult pathogen carriers have been described; this accounts for the numerous sources and pathways of infection transmission, both vertical and horizontal. The transmission risk depends on many factors, vaginal colonization in the parturient being of special import. The level of the pathogen adhesion to the barrier epithelium is reflective of the tissue sensitivity to infection. Increased sensitivity of the vaginal epithelium to B streptococci adhesion in association with the intake of some contraceptives has been found. The adhesive activity of avirulent streptococci B strains is shown to be higher than in the virulent strains, which is especially important in mixed virus bacterial infections. The streptococcal infection of high mortality is underlain by activation of persisting avirulent streptococci B that manifest their pathogenicity as a result of the virus-specific modifications in the host cell membrane. During 1985-1987, in Leningrad Institute of Gynecology and Obstetrics over 80 strains of streptococci B were isolated, the leading serotypes being Ia/C, Ib/C, II/C, III/R. Only 54% of the studied pregnancies attended with the streptococcus carriage had a favourable neonatal outcome. The strain serotypes from maternal isolates and abortuses fully correlated. Further improvement of the laboratory diagnosis and means of the pathogen and its carriers identification is a current priority.

Bacterial Adhesion↗
PubMed1989

[Dynamics of early morphologic shifts in the bronchopulmonary system in intranasal infection of mice with streptococcus group B].

When mice are intranasally infected with avirulent and virulent B streptococci, one may single out 2 phases of microbe interaction with bronchopulmonary tissue: 1) streptococcal adhesion, epithelial detachment and causative agent phagocytosis occur within the first 2 hours; 2) hematogenic phagocytes are involved in the process 5 or more hours later. Unlike avirulent streptococci, virulent ones frequently lead to the formation of destructive foci and are less actively phagocytized. On infection with avirulent strain, the microbes seed from the lung during 24 hours. The phagocytotic index and mean alveolar macrophage destruction values are in excess of the similar values seen in polymorphonuclear leukocytes, becoming lower on day 6 of postinfection.

Adenylyl Cyclases↗
PubMed1989

[The role of fibronectin in the streptococcal adhesion process].

The work shows that fibronectin obtained from human plasma is capable of binding with streptococci of different groups with almost equal effectiveness. Fibronectin bound to bacterial cells inhibits the adhesion of group A streptococci onto vaginal cells, but it produces no effect on the adhesion of group B streptococci. The binding constant of fibronectin 125I is equal to 10(6) -M-1, which indicates that the level of the specificity of interaction is not sufficiently high.

Bacterial Adhesion↗
PubMed1989

[Fatal synergism of viral-bacterial infections (a model of influenza-streptococcal infections)].

A model of virus-bacterial infection involving A (PR-8/34) influenza virus and group B streptococcus is proposed to demonstrate the cyclic manifestations of fatal synergism of the causative agents correlating with either the cyclic detection of influenza virus antigens in the infection focus on administration of avirulent streptococcal Fos4 strain, or with the time-course of activity shown by natural killers on administration of virulent streptococcal Fos8 strain. Based on the presented data on the cyclic character of fatalities, whose dynamics varies only slightly with the biological properties of the second agent, a conclusion has been derived on (1) the simultaneous influence of various factors in the formation of the mechanisms of infection transformation, (2) the capability of the cell receptor apparatus to respond to an external stimulus which is the most important of these mechanisms, and (3) the effects of the biological properties of the causative agents on the fatal effect manifestations.

Animals↗
PubMed1989

[Comparative aspects of adhesion of group A and B streptococci to human epithelium].

The international and original research data on the adhesion of group A and B streptococci are over-viewed. Based on the conducted studies, a conclusion has been drawn on the polyfactor pattern of pathogenic streptococci adhesions. The polyfactor pattern of adhesion is manifested in (a) different ranges of tissue sensitivity to streptococci adhesion, (b) a correlation between the adhesiveness and particular phenotypes (M(+)-M-; OF(+)-OF- in group A streptococci, TSA(+)-TSA- in group B streptococci), (c) different sensitivity of adhesives to proteolytic enzymes, and (d) interaction with fibronectin. M-protein was found to be involved in specific pyogenic streptococcal adhesion to the pharyngeal epithelium, which opens up new vistas for the search of approaches to the prevention of mucosal colonization. The participation of lipoteichoic acid (LTA) in group A and B streptococci adhesion in different tissues was shown The involvement of proteins in group B streptococcal adhesion was suggested by indirect evidence, which needs to be confirmed by direct isolation of an adhesive. It is suggested, that different quantitative combinations as well as structural organization of protein complexes and LTA in the streptococcus cell wall may determine the strain and species specificity of pathogenic group A and B streptococci interaction with host tissues.

Bacterial Adhesion↗
PubMed1988

[Biological properties of Streptococcus group B: the interrelations of the virulence in mice, the adhesion to human epithelial cells and the production of type-specific antigen].

The results presented in this work confirm the possibility of selecting the subpopulations of group B streptococci by the passage of these microorganisms through mice. This process was accompanied by the accumulation of cells with a high level of type-specific antigen (TSA). The passage of group B streptococci in the presence of type-specific antibodies led to the selection of avirulent microorganisms with low TSA production and high adhesiveness. These data may be considered to be the indirect evidence of the screening effect of TSA contained in the capsule of group B streptococci with respect to the ligand structures of these microbes. This suggestion is confirmed by the behavior of the variants of group B streptococci, obtained in the course of this investigation, on virus-infected tissue when TSA+ strains lost their ability to recognize viral polypeptides serving as receptors for TSA- variants of the streptococci.

Adult↗
PubMed1988

[A comparison of 2 methods for determining the hydrophobicity of Streptococcus groups A and B].

A simple method for the evaluation of the hydrophobic properties of streptococci, pathogenic for humans, by their adherence to polystyrene and a modified method for measuring their hydrophobic properties by their sorption on hexadecane have been developed. The results obtained in the evaluation of the hydrophobic properties of streptococci by these two methods have been compared and the complete correlation of these results in classifying the cultures as hydrophobic and hydrophilic has been shown. For the first time the differences in the hydrophobic properties of different strains of group B streptococci have been established.

Adsorption↗
PubMed1987

[Effect of the influenza A virus on the sensitivity of mice to infection caused by Streptococcus group B].

Study of the capacity of group B streptococci for causing the development of infection in mice has revealed the virulence of the cultures for mice to be determined by the serovar of the streptococcus, the infective dose, and the amount of type-specific polysaccharide. Under the conditions of mixed viral-bacterial infection, influenza A virus was shown to influence the development of bacterial infection in the animals in two ways: to increase the virulence of an avirulent strain and to decrease the pathogenicity of a virulent one in streptococcal monoinfections. Simultaneously with viral infection, the stimulation of the multiplication of an avirulent strain in the lungs of mice was observed, while in the control groups of the animals the elimination of bacteria from the lungs was registered. No additional accumulation of the infective virus in the lungs of mice in the presence of streptococci was found.

Animals↗
PubMed1984

[Adhesion of group B streptococci to vaginal epithelial cells].

The work presents the results of studies on the optimum and standard conditions for the in vitro determination of the adhesiveness of group B streptococci with epithelial cell suspensions. Vaginal epithelium has proved to be the most convenient and adequate system for studying the adhesiveness of group B streptococci. The optimum infective dose of these bacteria has been found to range from 50 to 200 cocci per cell. The characteristics of the adhesion of group B streptococci to vaginal epithelium are highly reproducible and exhibit low dependence on the time of the incubation of the bacteria with epithelial cells; fluctuations in the adhesiveness of the cultures in the definite range of pH shifts are seemingly determined by the serotype of the strains.

Adult↗
PubMed1977

[Interaction of group A streptococci with a culture of HEp-2 cells].

An initial stage of the interaction of the virulent (matt) and avirulent (glossy) strains of group A streptococcus with the human epithelial tissue (Hep-2) was studied. M+ and M- variants of three strains of group A streptococcus belonging to serological types 2 and 4 possessed different biological activity against the Hep-2 epithelial cells in the monolayer. M+-variant actively affected the great majority of the cells of the monolayer, multiplied of their surface and formed microcolonies. M--variant affected only an insignificant number of cells and failed to multiply on them. In difference from M+-streptococci, the activity of M+-variants is explained by their capacity to adhere to the surface of the animal cells irreversibly. This process started immediately and terminated by 1 1/2 hours of the microbial incubation in vitro with the Hep-2 monolayer. Trypsin treatment of M+-streptococci sharply diminished their capacity to adhesion, this apparently being the result of M-protein digestion. The data presented point to the important role played by M-protein in the phenomenon of the streptococci adhesion to the epithelial cells.

Cell Line↗
PubMed1977

[Characteristics of the virulence of a strain of S. typhimurium and its glycerin mutant in a HEp-2 cell line model].

Sensitivity of the HEp-2 cell culture to the infection with the virulent salmonella strains was shown; active penetration and multiplication of bacteria in the monolayer cells indicated this. Gly 90, a glycerine mutant defective by glycerokinase, obtained under the action of ethylmethanesulphonate, displayed a distinct difference from the initial virulent strains of salmonella by decreased invasive properties and the absence of any capacity to multiplication in the epithelial cells. The data on the avirulence of the glycerine mutant obtained on a model in vitro confirmed the observations carried out in vivo in intraperitoneal infection of albino mice (LD50 = 1-10(7) cells) and in keratoconjunctival infection of guinea pigs.

Animals↗
PubMed1977

[Experimental study, using a pulmonary model, of the pathogenic properties of genetically related strains of Sh. flexneri, differing in their ability to cause keratoconjunctivitis].

Complex microbiological and morphological study of the genetically connected Sh. flexneri strains, avirulent by keratoconjunctival test showed that the greatest extent of the virulent loss was revealed in shigellae with mutation in the area glpK-gene: they lost the capacity to penetrate into the cells of the bronchial epithelium, to resist local leukocytic reaction and to produce an injurious action on the pulmonary vessels. Shigellae with the replaced kcpA- gene area mostly lost the capacity to penetrate into the epithelial cells of mouse bronchi and were eliminated from the epithelium by the 9th hour after the administration. Xyl--avir-hybrids obtained from crossing of Sh flexneri with the streptomycin-resistant E. coli K12 donors were characterized by the loss of the capacity to prolonged reproduction in the organism of mice with the retention of the capacity to penetration into the epithelium, of the influence on the development of the leukocytic reaction and of the damaging effect on the pulmonary capillaries.

Animals↗