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S A Ermolaeva

Publications and source records attributed to S A Ermolaeva.

13 recordsLinked to original sources
PubMed2005

[The contribution of system regulation of pathogenicity-determining genes expression to the virulence of facultative intracellular parasites].

Bacteria which belong to the group of facultative parasites are capable of intensive proliferation both outside the organism and inside eukaryotic cells, thus often causing severe human and animal illness. The necessity of quick adaptation to the alteration of conditions after intrusion into the macro-organism gave rise to the development of complex genetic systems, regulating the activity of various gene groups. The review, written by the example of two pathogen bacteria, the gram-positive Listeria monocytogenes and the gram-negative Legionella pneumophila, illustrates up-to-date data that concern system regulation of genes, coding pathogenicity factors, as adaptive response of a bacterium to changes in outer conditions within the infectious process.

Animals↗
PubMed2005

[A new complex approaches for the identification of Listeria isolated during production of fermented sausages].

Distribution L. monocytogenes and other Listeria spp. in raw meat and during manufacturing of fermented meat products is investigated. The high contamination of raw materials and semi finished foods--in 36.5% of samples, ready-to-eat sausages--31.8% by Listeria spp. is established. Detection L. monocytogenes in 9.7% cases from the surfaces of equipment indicates the intensive circulation of listeriosis agents on meat plants. For identification 49 isolated strains the approach providing application of most informative for L. monocytogenes phenotypical tests (mobility, ability to haemolysis, presence of specific lecithinase) and assay based on PCR of DNA sites, coding phospholipase, factors of invasion and citotoxicity is used. Efficiency of this circuit is confirmed with positive results PCR with species-specific for L. monocytogenes primers to genes PIcA and ActA only at strains, having lecithinase and haemolysis activity. Application of the given approach has allowed to reduce in three times number of the cultures initially identified as L. monocytogenes on a complex of biochemical tests.

Colony Count, Microbial↗
PubMed2001

[Genetic mechanisms of Listeria monocytogenes virulence].

Current data on genetic determinants of virulence in Listeria monocytogenes and on factors affecting their expression are reviewed. The role of the PrfA protein, the only known transcriptional regulator that directly affects virulence gene expression and mechanisms responsible for the activity and/or concentration of this protein in the cell are considered. Detailed information of outer signals modulating the level of virulence factor expression is provided. Data that favor the involvement of autoregulatory processes in the expression of virulence genes are considered, and a model of regulation to explain these data is proposed.

Gene Expression Regulation, Bacterial↗
PubMed2000

[Changes in the virulence factor expression level in Listeria monocytogenes under various environmental conditions].

Effects of chelators Chelex-100 and activated charcoal on the production of proteins responsible for virulence of Listeria monocytogenes, facultative intracellular parasite were studied. Bivalent cation chelator Chelex-100 stimulates the production of only thiol-dependent hemolysin listeriolysin O. The presence of activated charcoal, a nonspecific chelator, in culture medium stimulated the expression of listeriolysin O and other main virulence factors by increasing the level of their transcription.

Bacterial Proteins↗
PubMed1998

[Ultrastructural and immunocytochemical study of Listeria monocytogenes with varying levels of pathogenicity factor production].

Wild and mutant strains of Listeria monocytogenes are examined by electron and immunoelectron microscopy. The mutant strain was characterized as a strain with a high level of production of pathogenic factors. No essential morphological criteria permitting the differentiation between wild and mutant Listeria strains were detected. Addition of activated charcoal to nutrient medium resulted in similar morphological changes in both strains. Enlargement of cells, a thicker cell wall, and changes in the cytoplasm structure are objective morphological signs of functional activity of bacteria with a higher level of pathogenic factor production. Indirect immunocytochemical method demonstrated the localization of specific phosphatidyl inosityl phospholipase C.

Bacterial Proteins↗
PubMedDate not supplied

[Autoregulation of expression of secreted proteins in Listeria monocytogenes].

The spectrum of proteins secreted by L. monocytogenes greatly depends on the composition of the cultivation medium. The introduction of activated charcoal (AC) into brain heart infusion (BHI) leads to the secretion of a number of additional proteins with mol.wt. ranging between 20 and 100 kD, whose production is not observed in pure BHI. The effect depends on the absorption capacity of AC: when adsorption capacity is reduced due to a decrease in the concentration of AC or its preliminary saturation with the components of the cultivation medium a drop in the level of the production of additional proteins is observed. The preliminary treatment of the medium with AC with its subsequent elimination prior to inoculation doses not change the spectrum of secreted proteins, though greatly inhibits the growth of L. monocytogenes. The data obtained in this investigation indicate that the effect produced by AC is based on the elimination of some product of L. monocytogenes vital activity from the cultivation medium; this product acts as the autoregulator of the synthesis of a number of secreted proteins.

Adsorption↗
PubMedDate not supplied

[Virulence factor expression regulation in Listeria monocytogenes].

The external and internal factors affecting the expression of L. monocytogenes virulence genes are analyzed. The role of protein PrfA, the only known factor directly affecting the transcription of virulence genes, as well as the contribution of other regulatory elements modulating the activity and/or intracellular concentration of PrfA are discussed. The environmental factors which influence the level of expression, such as temperature and the presence of metabolized carbohydrates in the cultivation medium, are analyzed. In addition, the possibility of autoregulating processes (the accumulation of L. monocytogenes-secreted autorepressor in the medium) is discussed and the possible mechanism of their action is suggested.

Animals↗
PubMedDate not supplied

[Listeria pathogenicity factors and their role in pathogenesis and laboratory diagnosis of listeriosis].

The mechanisms of relationships between Listeria and eukaryotic cells on the level of the main biomolecules are analyzed. These mechanisms determine the penetration and multiplication of Listeria and their importance for the pathogenesis of listeriosis. The theoretical and practical aspects of the regulation of the expression of pathogenicity factors in Listeria, connected with the activation of the regulatory protein PrfA and autoregulatory mechanisms, are considered. The elimination of the autorepressor from the cultivation medium results in the activation of the regulatory protein and the induction of the pathogenicity factors. The effective identification method for L. monocytogenes, permitting the differentiation of pathogenic and non-pathogenic Listeria, has been developed on the basis of the study of lecithinase expression in the presence of activated charcoal.

Animals↗
PubMedDate not supplied

[Effect of the constitutive activity of pathogenicity genes in Listeria monocytogenes].

The effect of the constitutive expression of pathogenicity factors in L. monocytogenes was studied on the model of the intraperitoneal infection of mice. The constitutive expression was due to a single amino acid substitution in the transcriptional factor PfrA, the master regulator of L. monocytogenes virulence genes. The effective lethal dose (LD50) for the strain with the constitutive expression of pathogenicity factors was 3 times lower than for the isogenic wildtype strain. When introduced in equal doses, this Listeria strain led to the death of the animals 1-2 days earlier than the wild-type stain. The study revealed that the constitutive expression of pathogenicity factors resulted in faster dissemination of bacteria in the body of the animal during the first 24 hours, but led to their earlier elimination from the internal organs at later stages of infection.

Animals↗
PubMedDate not supplied

[Genes, encoding invasion factors in Listeria monocytogenes strains isolated in the European part and the far east of Russia].

The collection of 76 Listeria monocytogenes strains isolated from humans, animals and food products was screened with PCR to reveal genes, which encode invasion factors of the internalin family. Obtained results demonstrated the correlation between the strain specific polymorphism of the revealed internalin genes and the source of the strain.

Animals↗
PubMedDate not supplied

[Cloning and expression of the phosphatidylinositol-specific phospholipase C gene from Listeria monocytogenes].

The gene for phosphatidylinositol-specific phospholipase C (PI-PLC) of Listeria monocytogenes has been cloned and shown to be expressed in Escherichia coli cells from own as well as from the lactose gene promoter. The recombinant plasmid has been constructed on the basis of pRIT2T vector and carries the hybrid gone. 3-end of which is a fragment of protein A gene of Staphylococcus aureus. 3-end is a gene for phospholipase plcA, both in the same reading frame. The resultant construction is shown to code in Escherichia coli cells for the hybrid recombinant protein A:Pl-PLC. Purified preparation of the hybrid protein and polyclonal rabbit antiserum to it were obtained. The obtained antiserum to the hybrid protein containing phospholipase as en C-end domain has been shown to react specifically to phospholipase in Escherichia coli recombinant strain harbouring the constructed recombinant plasmid as well as the one in the culture fluid of listeria.

Base Sequence↗
PubMedDate not supplied

[Species-specific detection of Listeria monocytogenes by directed DNA amplification].

A highly sensitive species-specific test system which allows detection Listeria monocytogenes in animal tissues is elaborated using the principle of a polymerase chain reaction. The potentialities of its application were studied in the conditions of experimental infection of animals. It is shown that while the procedure of detection is relatively simple and fast, the test system is as sensitive and specific as traditional microbiological methods.

Animals↗