[The rapid method for differentiating bacteria of Listeria strain].

An integrated indicator medium has been designed to differentiate Listeria bacteria from other microorganisms, which may be used at the first stage of diagnosis of the causative agent of listeriosis. The application of this medium makes it possible to simplify and to accelerate the detection of Listeria in the examination of different samples of foodstuffs, environmental objects, clinical material and to extend the range of Russian indicator culture media for the differentiation of this microorganism.

[Differentiantion of Listeria monocytogenes strains isolated in the Far East and European part of Russia on the basis of polymorphism of genes encoding invasion factors].

Forty Listeria monocytogenes isolates obtained in European and Far East regions of Russia were differentiated on the basis of polymorphism of 5 markergenes. Total length of concatemers obtained after sequencing of internal fragments of genes inlA, inlB, inlC, inlE and prs was 3029 b.p. Comparative analysis of concatemers' sequences revealed 237 variable nucleotides. Totally, 25 sequence types were revealed, and isolates from European and Far East regions belonged to different types. On the dendrogram isolates split on 2 clusters, which correspond to early described phylogenetic lines of L. monocytogenes specie. Isolates obtained in European and Far East regions formed independent subclusters within main clusters. Fifteen clinical isolates of L. monocytogenes belonged to 7 different types. Analysis of epidemiologic data on time and place of isolates obtaining suggested that isolates of the same sequence type are epidemiologically related and might represent one strain; index of discrimination for proposed typing method was calculated as 0.982.

[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.

[Adaptive ultrastructural changes in soil-resident Yersinia pseudotuberculosis bacteria].

After the prolonged residence (from 1 month to 2 years) in flow soil columns at 6 - 8 degrees C and 18 - 20 degrees C a complex of ultrastructural changes was detected in Y. pseudotuberculosis bacteria, depending on temperature, the duration of residence in the soil and, to a definite extent, on the strain. They were manifested in the form of cell-wall changes, the formation of the capsule and intercellular slime, changes in the ribosomal saturation of cytoplasm and the conformation state of DNA in the nucleoid zone. As the result of adaptation to nutritional deficit storage substances were accumulated in the form of electron-dense inclusions (polyphosphates) and pseudovacuoles (poly-beta-oxibutyric acid). Temperature influenced the process of mitotic division and the state of chromatin in bacteria. The described ultrastructural changes Y. pseudotuberculosis may be regarded as natural adaptive reaction to the altered conditions of their residence.

[Microbiological characterization of Listeria monocytogenes isolated from different sources in the Primorsky Territory].

The results of the bacteriological study of material, taken from humans, rodents, hydro-bios and environmental objects (including foodstuffs) in the Primorsky Territory, for the presence of L. monocytogenes bacteria are given. 83 bacterial strains of the genus Listeria were isolated. As revealed in this study, 25 of these strains belonged to L. monocytogenes (30.12%), 8 strains--to L. innocua (9.6%), 6 strains--to L. seeligeri (7.2%) and 2 strains--to L. ivanovii (2.4%). The greatest number of L. monocytogenes was isolated from foodstuffs and environmental objects. Some biological properties of L. monocytogenes were studied, the degree of their pathogenicity and sensitivity to antimicrobial preparations were determined.

Effect of temperature on synthesis of polyphosphates in Yersinia pseudotuberculosis and Listeria monocytogenes under starvation conditions.

It was found that at low temperature (6-8 degrees C) in the absence of nitrogen supply and at the presence of phosphate ions in the medium, Yersinia pseudotuberculosis and Listeria monocytogenes are able to actively synthesize reserve substances as polyphosphates. Most of the bacterial polyphosphates are alkali-soluble, especially at the preliminary stage of cell growth (lag-phase). This is proved by electron microscopic studies of ultrastructure of model microorganisms. During a long starvation period under conditions of carbon and energy source deficit, L. monocytogenes and Y. pseudotuberculosis consume this biopolymer for biosynthetic and bioenergetic processes.

[Investigation of relationships between marine diatoms and the bacterium Listeria monocytogenes].

Relationships between marine diatoms and the bacterium Listeria monocytogenes have been studied by routine algological methods and high-resolution video-enhanced differential interference contrast light microscopy. The study showed that the relationship between the listeria and the benthic diatom Navicula sp. has a parasitic character, whereas the relationship between the listeria and the planktonic diatom Phaeodactylum tricornutum is protocooperative.

[Experimental study on impact of salmon milt DNA on T-cellular immunity].

The impact of a biologically active food supplement containing salmon milt DNA on cellular immunity was experimentally studied. It was shown that the DNA had a dose-dependent stimulating effect on lymphocyte transformation, stimulated the DTH response and protected from experimental listeriosis infection.

[Influence of temperature on the variability of Listeria monocytogenes in the course of its prolonged existence in soil-packed water-circulating columns]. / Vliianie temperatury na izmenchivost' Listeria monocytogenes pri dlitel'nom obitanii v protochnykh pochvennykh kolonkakh.

The capacity of L. monocytogenes for prolonged existence in the soil at different temperatures (18-20 degrees C and 6-8 degrees C) has been shown. The viability of these bacteria in the soil depends both on their properties and the temperature factor. Low temperatures (6-8 degrees C) ensure, on the whole, the stable preservation of the biological properties of the bacteria. More pronounced variability of L. monocytogenes at a temperature of 18-20 degrees C is an adaptive property, ensuring high ecological plasticity of the bacteria and their prolonged existence in the soil.

Adaptation variability of Yersinia pseudotuberculosis during long-term persistence in soil.

Adaptation changes in the morphological and biological characteristics of pathogenic Yersinia pseudotuberculosis inhabiting a model soil ecosystem for a long time were studied. Changes in cultural, biochemical, and morphological characteristics of Yersinia and a decrease or loss of virulence were observed under these conditions. The detected changes were phenotypical, i. e. several passages in common nutrient media restored the original characteristics of the strain.

[Epidemiological hazards of low-temperature food storage]. / Ob épidemiologicheskoi opasnosti khraneniia pishchevykh produktov pri nizkoi temperature.

Refrigerator food storage lose its preventive value. This is particularly associated with the specific features of the pathogens of saprozoonosis which can easily adapt to low temperatures and feed deficit. Pseudotuberculosis agents were used to show that saprozoonosis pathogens can live and feed in a warm-blood being and in the environment. Their biological features require new approaches to controlling these infections.

[The biochemical mechanisms of energy support in Yersinia pseudotuberculosis cells at a low cultivation temperature]. / Biokhimicheskie mekhanizmy énergoobespecheniia kletok Yersinia pseudotuberculosis pri nizkoi temperature kul'tivirovaniia.

The object of the study was the first stage of biological oxidation: the transfer of hydrogen electrons to the components of the respiratory chain of Y. pseudotuberculosis cells by NAD and NADF, coenzymes of pyridine-dependent dehydrogenases, having labile redox properties. The study revealed that in the low-temperature cultivation of Y. pseudotuberculosis an increase in the content of NAD and NADF was 1.5- to 2.0-fold greater than that observed at 37 degrees C, which was indicative of the fact that at low environmental temperature pyridine-dependent dehydrogenases played a more important role than at high temperature (37 degrees C). This, in combination with other mechanisms, made it possible for bacterial cells to maintain the level of energy metabolism, necessary for their survival, in the environment with low and constantly changing temperature.

Ultrastructure of Yersinia pseudotuberculosis inhabiting the soil for a long time.

Ultrastructural changes in the population of pathogenic Yersinia pseudotuberculosis inhabiting a model soil ecosystem for a long time were studied. Changes in the bacteria were mainly adaptive until the 8th month of the experiment, their capacity to binary division was preserved. After 9 months cell structure changed: extracellular amorphous matrix appeared, probably due to increased mucus production.

[Effect of cultivation temperature on nucleic acid level in bacteria Listeria monocytogenes and Yersinia pseudotuberculosis]. / Vliianie temperatury kul'tivirovaniia na soderzhanie nukleinovykh kislot u bakterii Listeria monocytogenes i Yersinia pseudotuberculosis.

The relationship between the multiplication of bacteria, the content of nucleic acid and the specific rate of their growth during their batch cultivation in nutrient broth and mineral medium at temperatures of 37 degrees C and 4-6 degrees C was studied in the causative agents of saprozoonotic infections with L. monocytogenes and Y. pseudotuberculosis used as typical representatives of such bacteria. The content of DNA was shown to remain practically unchanged after the alteration of cultivation temperature and the conditions of nutrition. The linear relationship between the content of RNA and specific growth rate was registered both at 37 degrees C and 4-6 degrees C. However a higher content of RNA at low temperatures was found to correspond to one and the same specific growth rate, which was linked with the additional synthesis of this nucleic acid.

Autotrophic assimilation of CO2 and C1-compounds by pathogenic bacteria.

We demonstrate for the first time that the pathogenic bacteria Yersinia pseudotuberculosis and Listeria monocytogenes (pathogens of saprozoonoses) are capable of chemolithoautotrophic assimilation of CO2. Low temperature is favorable for better absorption of CO2 by these bacteria; this is supported by increased enzymatic activity of carbonic anhydrase acting as the supplier of the substrate to the site of carboxylation. Data of radioisotopic methods indicate that assimilated labeled carbon of CO2 is incorporated into all major cell biopolymers. The bacteria can utilize not only CO2, but also other C1-compounds for biosynthesis.

[Highly purified agar for virological, immunochemical and microbiological research]. / Vysokoochishchennyi agar dlia virusologicheskikh, immunokhimicheskikh i mikrobiologicheskikh issledovaniiakh.

A new effective method for the preparation of highly purified agar for microbiological, virological and immunochemical investigations has been obtained and the technology for its production has been developed. The study revealed that the physico-chemical characteristics of newly obtained highly purified agar are much better than those of microbiological agar currently produced in Russia and not inferior to those of the best kinds of agar produced by Difco (USA), Serva and Ferak (Germany). The method of purification is protected by an author's certificate. The production of this agar for medical purposes has been permitted. The manufacturing plant "Medbioagar", created under the auspices of the Research Institute of Epidemiology and Microbiology has now started the serial production of highly purified agar under the name "Primagar". Further increase of the production of the preparation will facilitate its introduction into laboratory practice with the use of modern research methods in the fields of microbiology and virology, molecular biology and genetics, immunology and biochemistry.