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V I Pushkareva

Publications and source records attributed to V I Pushkareva.

At least 19 recordsLinked to original sources
PubMed1992

[Pseudomonads as parasites of protozoa].

The experimental study of the interaction of Tetrahymena pyriformis with different microorganisms of the genus Pseudomonas, isolated from the soil, was made. The study revealed that T. pyriformis phagocytosed some Pseudomonas pigment-forming species (P. cepacia, P. putida, P. fluorescens, P. pirkettii). The most pronounced cytopathogenic effect was produced by P. cepacia. The dynamic observations of the ultrastructural features of interaction between P. cepacia and protozoa were made. Even at early stages of this interaction some types of parasitiferous phagosomes containing both intact bacteria capable of multiplication by binary division and Pseudomonas cells exhibiting different degrees of destruction were registered. In several phagosomes morphologically intact bacteria differing in their cell-wall profiles and the density of their cytoplasm and nucleotide were present simultaneously. More dense cells with sinuous cell-wall membranes were more virulent. By hour 18 one giant parasitiferous vacuole was formed by fusion of smaller phagosomes, which subsequently broke up, liberating a new generation of bacteria. In infected cells disturbances in the structure of their mitochondria and macronucleus appeared. During the first 2 days of the joint cultivation of P. cepacia and T. pyriformis the accumulation of bacteria occurred due to the selection and multiplication of digestion-resistant bacterial cells, which ensured the resistance of this Pseudomonas population in association with protozoa.

Animals↗
PubMed1991

[An experimental study of Yersinia in plants].

Y. enterocolitica and Y. pseudotuberculosis have been experimentally found to penetrate into plants (cabbage, salad, pea, oat) from infected soil and water and to remain in different plant organs (roots, seeds, leaves) up to 30 days (the term of observation). The processes of S-R dissociation in Yersinia cultures isolated from plants, as well as changes in some enzymatic properties, have been established. In the test on Infusoria the cytotoxic action of strains isolated from plants has been noted. The possible role of plants in carrying pathogenic bacteria from the soil to the surface ecological systems and the subsequent infection of animals and humans is discussed.

Animals↗
PubMed1990

[An analysis of the mechanisms of interpopulation interaction of Yersinia with Tetrahymena pyriformis infusorians at the cellular and subcellular levels].

The mechanisms of interaction between the populations of Yersinia and T. pyriformis have been analyzed on the cellular and subcellular levels. As shown in this investigation, Yersinia, when phagocytized by T. pyriformis, may undergo morphological changes, remain unchanged and also multiply, destroying the host cell in the process.

Animals↗
PubMed1990

Analysis of factors which determine the existence of Yersinia pseudotuberculosis in a saprophytic phase.

Data are presented on the effects of a variety of abiotic and biotic environmental factors on the existence and changes in the numbers of Y. pseudotuberculosis. Experiments with sterile soil showed that Y. pseudotuberculosis populations were resistant over a wide range of major abiotic factors: temperature (0-30 degrees C), humidity (15-50%), pH (5.9-9.0). Although exerting some effect on the duration of different growth phases, the above abiotic factors did not influence, within the tested range, the general nature of populational dynamics of the microbe. Comparative experiments carried out in sterile and natural soil specimens using an RNA-polymerase mutant warranted the conclusion that the numbers of Y. pseudotuberculosis in soil (water) are largely controlled by the biotic components of ecosystems, including microflora and microfauna. Y. pseudotuberculosis was shown to exist in the environment (vegetable storehouses and substrate of rodent nests) in association with bacteria belonging to the family Enterobacteriaceae as well as the genera Acinetobacter and Pseudomonas. Endosymbiotic relationships are described between Y. pseudotuberculosis and the free-living infusorian Tetrahymena pyriformis which sustains microbial populations in the soil (water).

Animals↗
PubMed1990

[Yersinia in the water of wells near an area of irrigation with the effluents from a swine-breeding farm complex].

Water taken from wells situated in the zone of irrigation with sewage water from a swine-breeding complex was studied. In 25.4% of samples Y. enterocolitica and Y. intermedia were detected. In winter and spring months twice as many strains were isolated in comparison with the number of strains isolated in summer and autumn. No Yersinia were isolated from control water samples taken from wells remote from the irrigation zone. The epidemiological relationship between a case of Yersinia infection and the use of infected well water was established.

Agriculture↗
PubMed1986

[Immunogenicity of a chemical typhus vaccine and of a corpuscular radioantigen obtained from Rickettsia prowazekii].

The protective activity of chemical typhus vaccine and R. prowazekii corpuscular radioantigen (CRA) was studied. Guinea pigs were immunized with doses of 32 and 48 antigenic units. Antibody production was assayed in the complement fixation test. On days 7, 15, 21, 30 and 60 after immunization the animals were challenged with R. prowazekii introduced in an amount of 10(5) minimum embryonal infective doses (MEID). On day 30 some of the animals were challenged with 10(3) MEID of R. typhi. The results demonstrated that both preparations were highly immunogenic and capable of protecting most of the animals from 10(5) MEID of R. prowazekii. Immunity developed earlier after immunization with CRA. The guinea pigs immunized with CRA, purified in percoll density gradient, and challenged with 10(3) MEID of R. typhi on day 30 showed a high level of cross immunity. In all control animals high fever and periorchitis were observed.

Animals↗
PubMed1985

Histological changes in mouse liver and spleen caused by different Coxiella burnetii antigenic preparations.

The effect was examined on mouse liver and spleen (inbred line A) of intraperitoneal (i.p.) inoculation of phase I Coxiella burnetii (C.b.) cells either untreated or treated with chloroform-methanol (CM) mixture in comparison to the trichloracetic acid extract (TCAE) from phase I C.b.) cells. The phase I C.b. cells were highly toxic as manifested by marked hepatosplenomegaly accompanied with hyperplastic, degenerative and necrotic changes in the liver. By contrast, phase I CM--treated C.b. cells and TCAE were nontoxic as evidenced by the absence of any distinct pathological changes in mouse viscera.

Animals↗
PubMed1980

[Macrophage migration inhibition reaction in Marseilles fever].

Delayed type hypersensitivity (DTH) was studied in the macrophage migration inhibition test, antibody titers in the CFT and functional activity of spleen macrophages, obtained from guinea-pigs infected with R. conori, in cell cultures. No direct correlation between antibody synthesis and functional macrophage activity accompanied by the development of DTH was revealed. The most pronounced protective function of macrophages could be observed during the decrease of antibody titers and the extinction of DTH.

Animals↗
PubMedDate not supplied

[Effect of blue-green alga (Cyanobacteria) and their exometabolites on formation of resting forms and variability of Yersinia pseudotuberculosis].

Research, carried out with the use of bacteriological methods and polymerase chain reaction, revealed that the transformation of Y. pseudotuberculosis, associated with blue-green algae Anabaena variabilis, into resting (noncultivable) forms took shorter time than in soil extract containing no algae. The exometabolites of "old" cultures of these algae sharply accelerated the formation of resting Y. pseudotuberculosis forms. The influence of the algae and the products of their metabolism was manifested far more intensively at 22 degrees C than at 4 degrees C. After passage through infusoria resting Y. pseudotuberculosis forms, preserved in the mucous covering of cyanobacteria, partially reverted into vegetative forms, capable of growing on solid culture media. The revertants essentially differed from the initial vegetative forms by having lower enzymatic activity, agglutinability and cytopathogenicity, as well as by the loss of plasmid p45. The probable role of blue-green algae, widely spread in soils and water reservoirs, in the processes of reversible transformation of Y. pseudotuberculosis vegetative and resting forms, closely connected with seasonal changes of temperature conditions.

Biological Factors↗
PubMedDate not supplied

[Ecological-genetic mechanisms of the transition of Salmonella typhimurium to the dormant state in the environment].

The dynamics of vegetative and dormant (noncultivable) of S. typhimurium cells of two isogenic strains in association with microalgae Scenedesmus quadricauda and under the action of the exometabolites of the algae at different stages of their growth was studied using in parallel bacteriological method and PCR. The study revealed that at the stage of active growth green algae and their metabolic products maintain the survival of salmonellae (strain TR = 1) vegetative forms in water at an optimum temperature. Low temperatures induced their gradual (3 weeks) transition to the dormant state. The exometabolites of old dying algae induced the rapid (several hours) and complete transition of the bacterial population (TR = 1) to noncultivable state. In our experiments the insertional mutation in gene pqi (strain PhoA = 8), inducing the defect of transmembrane protein and disturbances in the transition of salmonellae to dormant state, led to stable existence (lasting 7 months, i.e. the whole term of observation) of vegetative cells. The natural inducers tried in our experiments did not lead to the formation of the dormant forms of salmonellae in this mutant strain.

Acclimatization↗
PubMedDate not supplied

[Ultrastructure of Yersinia pseudotuberculosis in the process of their reversible transition into the dormant (non-culturable) state in association with blue-green algae].

The ultrastructural organization of Y. pseudotuberculosis in the process of the transition of vegetative cells into the dormant (noncultivable) state in interaction with blue-green algae of the species Anabaena variabilis was studied by the method of transmission electron microscopy. The use of type specific Y. pseudotuberculosis serum made it possible to identify Y. pseudotuberculosis cells in the bacterial association and to find out whether their antigenic properties remained intact in time. The dormant forms of Y. pseudotuberculosis, recultivated by passage through the axenic culture of unfusoria (Tetrahymena pyryformis), were also studied with the use of electron microscopy. The revertants were found to be at different stages of restoration of their typical morphological characteristics and antigenic properties were partially retained. The fine structure of Y. pseudotuberculosis cells in the initial culture was shown to be similar to that of the revertants of dormant forms, morphological criteria of the dormant cell ultrastructure were established. The cyclic processes of reversible transition from vegetative forms to dormant ones in bacterial populations under the influence of hydrobios is regarded as an adaptive mechanism of their existence in the environment.

Adaptation, Physiological↗
PubMedDate not supplied

[Experimental evaluation of interaction between Yersinia pestis and soil infusoria and possibility of prolonged preservation of bacteria in the protozoan oocysts].

The character and outcome of interactions between Y. pestis (vaccine strain and soil infusoria Tetrahymena pyriformis (axenic culture) were under experimental study. The parallel use of the bacteriological method and PCR test systems made it possible to follow the dynamics of Y. pestis cells (strain EV) with different plasmid profiles in their interaction with infusoria, as well as their passage into the protozoa cysts. The study revealed the complete utilization of Y. pestis cells lacking virulence factors by infusoria. The presence of plasmids of virulence influenced only the duration of complete bacterial phagocytosis. A drop in the temperature of cultivation to 2 degrees C induced the mass and rapid encystment of infusoria. In the PCR analysis specific DNA fragments of Y. pestis cells, preserved in the latent (uncultivable) state, were detected in the cysts of protozoa within the period of up to 14 months, while the results of bacteriological studies were negative. The data thus obtained are discussed with regard to the possible mechanisms of the existence and prolonged reservation of Y. pestis in the soils of natural foci with participation of protozoa.

Animals↗
PubMedDate not supplied

[Variability of the clonal structure of Yersinia pseudotuberculosis population under different conditions].

In a series of experiments the dynamics of the clonal structure of Y. pseudotuberculosis population was evaluated by cytopathogenicity in soil extract, as well as in associations with blue-green algae (cyanobacteria) and infusoria, under different temperature conditions. In all variants of experiments made at low environmental temperature (10 degrees C) a considerable part of Y. pseudotuberculosis clones (25-40%) was found to be cytopathogenic, while at 22 degrees C such clones were absent or had low cytopathogenicity. At the same time experiments made under the same temperature conditions (10 degrees C) showed the variability of the clonal structure of the bacterial population in different associations and sterile soil extract, as well as at different periods of the experiments. At low temperatures Y. pseudotuberculosis virulent (cytopathogenic) clones, in contrast to avirulent ones, were characterized by the presence of virulence plasmid p45, as well as high urease and catalase activity. The results of the experiments are discussed from the viewpoint of the clonal concept of bacterial populations and their pathogenicity.

Animals↗
PubMedDate not supplied

[Biocenosis of the natural foci of sapronotic infections (the results of 15-year observations)].

The summarized results of original studies, carried out in 1988-2003 by scientists of the Gamaleya Research Institute of Epidemiology and Microbiology, are discussed. The part dealing with the regularity and mechanisms of the circulation of pathogenic bacteria in the biocenosis of soil and water reservoirs includes the following subjects: population and intracellular interactions with protozoa; the evaluation of different representatives of hydrobios as hosts and the transmission along trophic biocenotic chains; the effect of algae and their metabolic products on bacterial populations; the possibility of the colonization of higher plants from the soil and the subsequent infection of rodents; the variability and clonal structure of bacterial population in its interaction with protozoa and plants; the chain of Yersinia circulation in agrocenosis. The part dealing with the mechanisms of the prolonged reservation of causative agents includes such subjects as the reversible transition of bacteria into the latent (uncultivable) state in soils and water reservoirs, as well as the biological inductors of this process; the prolonged preservation of latent bacteria in the cysts of protozoa and blue-green algae; the indication of causative agents in the natural foci of plague and pseudotuberculosis. On the basis of the original investigations and the data of literature new theoretical review in the field of the natural foci and the epidemiology of sapronotic infections have been formulated.

Adaptation, Physiological↗
PubMedDate not supplied

[Burkholderia cepacia under different ecological conditions: the amount and variability of the bacterial population].

In a series of prolonged experiments with the use of the bacteriological method and PCR analysis the amount and state of B. cepacia population, associated and not associated with infusoria Tetrahymena pyriformis, were dynamically evaluated under different conditions: in water, brain heart broth, soil extract and at different temperature (4 degrees C and 25 degrees C). In soil extract at 25 degrees C B. cepacia existed in the vegetative state for the period of up to 3 months, while at 4 degrees C, in the absence of protozoa, the transition of these microorganisms into the uncultivable forms occurred in 9 days, and they could be detected only with the use of PCR. Protozoa maintained the existence of the vegetative bacteria for as long as 2 months, and in 3-4 months uncultivable forms of B. cepacia cells were registered. In water at low temperature B. cepacia disappeared in 2 months, evidently, eaten up by infusoria. The population variability of B. cepacia under different conditions of their existence was established: S-R dissociation, a decrease in biochemical activity, growth deceleration. A high level of cytopathogenicity in B. cepacia pigment-forming clones was noted. In the process of transition into the uncultivable state pigment formation in B. cepacia population decreased up. The ecological plasticity and multi-pathogenicity of B. cepacia as phytopathogens and the causative agents of human diseases are discussed.

Animals↗