[Epizootological assessment of the possibilities of importing plague from Vietnam to Russia].

To assess whether the plague microbe with vectors or carriers can be imported from Vietnam to Russia, the authors consider the specific features of pathogen circulation in this country's biotopes varying in anthropogenic transformation. The idea that there were natural foci of plague in Vietnam dominated until the late 1990s. The small rat Rattus exulans that inhabits open stations and ensures a parasitic contact with the synanthropic representatives of the fauna was considered to be a major carrier. The recent years have provided conclusive proofs that plague foci are absent in Vietnam wild nature. Anthropurgic foci develop in the network of localities whose conditions are favorable to the existence of synanthropic rodents and the fleas Xenopsylla cheopis. Cases of the plague pathogen, FI antigen and its antibodies being detected in wild mammals are due to their parasitic contacts with synanthropic rats in the agrocultural area around the localities with running epizootias. These contacts are provided by X.cheopis only. Since 2003, there have been no reports on the incidence of human plague or its pathogen isolation from environmental objects in Vietnam. However, all conditions and prerequisites for the formation ofanthropurgic plague foci remain in this country. Further epizootological monitoring is required for appropriate services to rapidly and adequately respond if the epizootological or epidemiological situation of this infection changes.

[Natural foci of plague in India: epizootological characteristics].

In the first half of the 20th century, India was responsible for the incidence of plague in both Asia and the world. The early 21st century was marked by two new epidemic outbreaks of plague (in 2002 and 2004) in this country. The major characteristics of plagues in India, activation of which is a cause of new epidemic outbreaks and necessitates a continuous epizootological monitoring, are analyzed. Historical experience shows that lower focus on surveillance of natural foci of plaque, dissemination of unjustified views on sanitation of endemic areas, and much less their lack, can cause unpredictable epidemiological complications and considerable costs. More scrupulous attention should be given to the importation of goods from North and South India (where there were outbreaks of plague in 1994, 2002, and 2004) to Russia mainly in September to March.

[Modeling of interaction between Yersinia pestis and Tetrahymena pyriformis in experimental ecosystems].

Modeling of interaction Yersinia pestis-Tetrahymena pyriformis in artificial soil ecosystem (ASE) containing soil of burrows of main carrier from Gorno-Altayski natural plague reservoir, as well as in physiological solution (PS) and in Hottinger broth (HB). Optimal proportion of bacterial and protozoa cells was possible to obtain and depended from virulence of Y. pestis and environmental conditions. In ASE at 18-22 degrees C association was the most stable under the microbial burden of 100 microbial cells (m.c.) per infusorian. Resistance of plague agent to phagocytosis by T. pyriformis was determined by strain's virulence. Avirulent strain Y. pestis [cyrillic letter: see text]-2377 was rapidly eliminated by protozoan in HB, PS and in ASE under the burden of 10 m.c per infusorian. Y. pestis [cyrillic letter: see text]-3443 with selective virulence compared with [cyrillic letter: see text]-2377 preserved in association longer in any tested medium. Highly virulent Y. pestis [cyrillic letter: see text]-3448 was the most resistant to phagocytosis by T. pyriformis.

[Plague in China. Threat of transmission to regions of Siberia and Far East].

In China plague has been officially registered from 1754 (638 epidemics with total number of cases 2.5 millions and case-fatality rate 87.5%). Endemic areas started to form on the south of the country and then the disease gradually spread on seaside provinces, where to the end of the 19th century, due to reach of island territories and large international seaports, was characterized by pandemic spread. Epidemic manifestations of plague in China were observed during more than 200 years in 23 out of 36 administrative areas affecting continental and North-Eastern regions of the country, which are immediately adjacent to border of Russia. Pneumonic plague in Manchuria clearly demonstrated the role of transport communications in transmission of this deadly infection and possibility of its spread on border regions of Siberia and Far East. Lengthy country's border, intensive migration flows, large-scale international integration, developing of near-border trade, simplification of policy for transboundary traveling are the reasons for differentiated number of sanitary protective measures on administrative borders of Siberia and Far East.

[Clonal structure of Yersinia pestis populations in experimental soil ecosystems].

Two basic tendencies--formation of latent (uncultivable) form (LF) and hemin storage variability--has been revealed during study of clonal structure dynamics of Y. pestis populations in artificial soil ecosystems in long-term incubation conditions. Y. pestis populations disappeared within 3 - 6 months at 18 - 22 degrees C, whereas at 4 - 8 degrees C a subsequent replacement of vegetative cells on LF, which are capable to prolonged survival (up to 22 months) in soil with ability to reversion in the presence of abundance of nutrients, has been observed. Bacteria of virulent strain retained all determinants of pathogenicity when reverted to LF, whereas bacteria of avirulent strain (defective on plasmid of Ca-dependence), on the contrary, undergo further degradation that resulted in loss of a pgm locus and gradual disappearance of population. LF revertants of highly virulent strain restored properties of initial population and were highly virulent.

[Genotyping of Yersinia pseudotuberculosis isolated in Siberia and Far East].

Genotypic characteristics based three main factors of pathogenicity (presence of resident plasmids [pYV, pVM], gene of toxin-superantigen ypm and nine genes for high pathogenicity island [HPI]) of 212 strains of Y. pseudotuberculosis isolated in Siberia and Far East were studied. It was shown that strains of Y. pseudotuberculosis with one of two variants of plasmids 82:47 MDa and 47 MDa (60.8% and 31.6% respectively) are predominated. Gene ypmA was detected in 96.2% of isolated strains. Eight strains had none of the ymp gene variants. HPI were detected in 96.2% of isolated strains. Obtained characteristics of Y. pseudotuberculosis allowed to determine the dominating genogroup pWYV+, ypmA+, HPI- (95.8% of strains) that cause systemic infection.

[Evolution of the epidemiology of cholera].

The problems of the evolution of cholera at the stages of its pandemic spread are described. A short characterization of endemic zones in the countries of Asia, Africa and Latin America, stipulating the preservation of infection and the appearance of periodic epidemics in the world, is presented. Special attention is paid to the genesis of epidemic outbreaks in endemic and introduced foci of cholera, differing in the specific features of their formation and the accumulation of the epidemic variant of the infective agent in aqueous habitat. The role of the ecosystem of surface water reservoirs in the prolonged survival of cholera vibrios is evaluated. The necessity of the detailed study of the mechanisms and forms of existence of serogroup 0139 vibrio in open water reservoirs is substantiated. In the system of epidemiological surveillance on cholera the microbiological monitoring of environmental objects assumes the leading importance.

[The population variability of Yersinia pestis in soil samples from the natural focus of plague].

Three Y. pestis strains were found to exist in the experimental soil ecosystem at a temperature of 4 degrees - 8 degrees C for a longer period (10 months, the term of observation) than at room temperature (3.5 months). Y. pestis population structure was characterized by relative stability in strains of the subspecies altaica and heterogeneity in the strain of the main subspecies, manifested by the loss of the pgm locus by vegetative cells and the preservation of pgm+ variants in the latent (uncultivable) form (LF). In the populations of all strains uniformity in calcium dependence, the tendency towards a decrease in the synthesis of factor 1, nutritional requirements in amino acids was observed. An important factor of the preservation of Y. pestis in the soil was LF formation. At room temperature this process quickly resulted in the death of the population. At 4 degrees - 8 degrees C A. pestis altaica avirulent strain could be inoculated onto solid nutrient media for a two-fold longer period (for 4 month) than the strain with selective virulence and for 5.5 months longer than Y. pestis pestis highly virulent strain.

[Ecological regularities of the existence of pathogenic Yersinia in soil ecosystems].

In this review the data on the ecology of pathogenic Yersinia in soil ecosystems, based on prolonged observations, were analyzed and summarized. In contrast to saprophytic species, ubiquitously spread in nature, pathogenic representatives of the genus Yersinia occurred only in the soil of natural foci and of these, Y. pestis were found only in the soil of burrows of the main carriers. The complex of abiotic and biotic factors (temperature, humidity, chemical composition, interactions in biocenosis) which determined the possibility of the existence of Yersinia in the soil environment and the preservation of their pathogenic properties was considered. Special attention was paid to their geno-phenotypic variability as the main factor of the adaptation of the causative agents of plague, pseudotuberculosis and intestinal yersiniosis in the environment.

[Experimental non-culturable Vibrio cholerae eltor and its biological properties]. / Eksperimental'noe poluchenie nekul'tiviruemykh form Vibrio cholerae eltor i kharakteristika ikh biologicheskikh svoistv.

In experiments with the cultivation of V. cholerae eltor under the conditions of high salt concentration, as well as low temperature and deficiency in nutrient substances, uncultivable forms (UF) of toxigenic and nontoxigenic vibrios were obtained. The absence of growth of seeded vibrios after the filtration of samples (with a filter of 0.22 micron), the preservation of specific antigenic determinants and the initial set of genes, changes in the morphology of cells (small size, coccoid form with the flagella retained) confirm the transition of V. cholerae eltor under study into the uncultivable state which, under unfavorable conditions, more rapidly develops in toxigenic vibrios than in nontoxigenic ones. The analysis of the INT-reductase activity of UF disintegrates revealed that they had endogenic respiration whose activity increased (4.5- to 6.5-fold) in the presence of the exogenic intermediates of the Krebs cycle. The uncultivable forms of the vibrios retain genes responsible for pathogenicity, as well as their antigenic determinants.

[Evaluation of the polymerase chain reaction effectiveness in the investigation of out-breaks of pseudotuberculosis]. / Otsenka éffektivnosti polimeraznoi tsepnoi reaktsii pri rassledovanii vspyshek psevdotuberkuleza.

Data on the investigation of pseudotuberculosis epidemic outbreaks with the use of the polymerase chain reaction (PCR), are presented. Specific fragments of Yersinia pseudotuberculosis DNA were detected in 81.25% of patients, in 46.83% of cases confirmed by the isolation of Y. pseudotuberculosis cultures. The study of washings from vegetables and equipment in vegetable stores and kitchens yielded positive results in PCR in 8.52% and the survey of rodents--in 3.85% of cases. In the course of the bacteriological study of these specimens 6 Y. pseudotuberculosis cultures were isolated: 3--from vegetable products, 1--from a Norway rat and 2--from house mice. The coincidence of the data obtained by bacteriological study and PCR showed that the latter method gave objective results, while being capable of ensuring rather rapid analysis. PCR should be regarded as a signal test for the bacteriological search of the definite infective agent in the material under study.

[Impact of Yersinia pseudotuberculosis on the in vitro production of cytokines by whole blood cells of donors]. / Vliianie Yersinia pseudotuberculosis na produktsiiu tsitokinov kletkami tsel'noi krovi donorov in vitro.

The impact of two plasmid (47, 82 MD), single plasmid (47 MD) and non plasmid Y. pseudotuberculosis strains, Y. enterocolitica (47 MD) as well as Y. pseudotuberculosis superantigen (YPM) on the production of interleukin-1 (IL-1), interleukin-6 (IL-6), interferon-alpha (IFN = alpha) and tumor necrosis factor alpha (TNF-alpha) by whole blood cells obtained from donors was studied. All Y. pseudotuberculosis and Y. enterocolitica strains stimulated the production of IFN-alpha, IL-1, IL-6 and TNF-alpha by whole blood cells, but considerably less than Y. pseudotuberculosis lipopolysaccharide and YPM. These data are indicative of the pathogenetic role played by 82 MD plasmid in manifestation of Y. pseudotuberculosis immunosuppressive properties. The maximum stimulation of the production of cytokines was observed under the action of YPM, which confirmed an important role played by this superantigen in the pathogenesis of Y. pseudotuberculosis.

[Epidemiological aspects of leptospirosis in the eastern regions of the Russian Federation]. / Epidemiologicheskie aspekty leptospirozov v vostochnykh regionakh Rossiiskoi Federatsii.

There have recently substantial changes in the basic parameters of Leptospira infection in the eastern regions. The infection is characterized by a pronounced and steady-state rise in morbidity rates, by its trend for urbanization, by the spread of the disease in recreational areas, by a primary role of dogs as sources of infection, by polymorphism and atypical nature of the clinical picture of Canicola leptospirosis, which make its diagnosis difficult. The anthropurgic foci where dogs and pigs are the main sources of pathogenic leptospiras are of the leading epidemiological significance. The optimum package of measures reducing a risk of human infection is recommended.

[Mode of sample preparation for pseudotuberculosis laboratory diagnosis by polymer chain reaction method]. / Sposob podgotovki prob dlia laboratornoi diagnostiki psevdotuberkuleza metodom polimeraznoi tsepnoi reaktsii.

A mode of feces sample preparation was developed for polymerase chain reaction (PCR) assay. It was based on alkaline treatment of the material. This treatment killed the most part of indigenous microflora, whereas Yersinia survived, because it was relatively resistant to alkaline. The mode was tested using human feces artificially contaminated with Yersinia pseudotuberculosis. Positive responses in samples containing 10(3)-10(8) microbial cells per ml were obtained by PCR assay with Yersi and Yers2, Invl and Inv2, YP3 and YP4 primers. Diagnostic efficiency of PCR for patients, small mammals, and washings from environmental objects was 4.75, 1.66, and 2.12 times higher than diagnostic efficiency of bacteriological analysis of these samples, respectively. Positive results in PCR were obtained at the day of the material collection and treatment, whereas Y. pseudotuberculosis was isolated only after 8-20 days. Positive samples in PCR and in bacteriological analysis were found to coincide. A brief scheme of the Y. pseudotuberculosis laboratory diagnosis is suggested. According to this scheme, target-oriented bacteriological assay is performed only in those samples, in which preliminary PCR assay after 1-3 days of incubation gave positive results of Y. pseudotuberculosis DNA detection.

[PCR-detection of markers for epidemiologically-significant strains of Vibrio cholerae 0139, isolated in Siberia]. / PtsR-detektsiia markerov épidemicheskoi znachimosti shtammov Vibrio cholerae 0139, izolirovannykh v Sibiri.

Fourteen V. cholerae 0139 strains were isolated in 1996-1999 in Siberia from the Ob river (Novosibirsk) and bogs and lakes (Irkutsk). The strains were tested in PCR for the key virulence determinants (ctx AB, tcp, acf). The genomes lacked these elements, and therefore the strains were acknowledged avirulent. The results correlate completely with the data of phenotypical analysis, characterizing the pathogenic characteristics of isolated strains.

[Eltor cholera in Latin America]. / Kholera El'tor v Latinskoi Amerike.

Cholera epidemics in South and Central America in the period 1991-1999 are characterized. The mechanisms of existence of Vibrio eltor in environmental objects have been substantiated. The causes and conditions of endemic foci formation which determine the infection spread not only within the countries of the subcontinent, but also far beyond its borders are shown. The effectiveness of cholera control interventions is evaluated.

[Strategies of adaptive changes in Vibrio cholerae in natural water reservoirs]. / Strategiia adaptivnoi izmenichivosti kholernykh vibrionov v prirodnykh vodoemakh.

The currently available data on different variations in cholera vibrio habiting in water reservoirs are summarized. The pattern of variations of the main signs of vibrions is discussed in the context of "typical-atypical-inactive-resting (uncultivable) forms". Emphasis is placed on the reversible pattern and adaptive essence of variation whose basis is clonal and selective processes in the heterogeneous bacterial population. Possible populational mechanisms responsible for the development of epidemic types of cholera vibrions in the aqueous ecosystems as a prerequisite for human morbidity are discussed. The efficiency of ecological and molecular genetic studies for the epidemiology of cholera is recognized.

[Cholera in the Far East of Russia. Communication 1. Epidemiological characteristics of the outbreak of cholera El tor in Vladivostok]. / Kholera na Dal'nem Vostoke Rossii. Soopshchenie 1. Epidemiologicheskaia kharakteristika vspyshki kholery él'tor v g. Vladivostoke.

The materials on the investigation of the outbreak cholera eltor in Vladivostok, caused by the import of infection from China. The leading role of the water route of transmission of this infection is shown due to the contamination of water sources with non-decontaminated sewage water. The complex of antiepidemic measures was carried out, which made it possible to arrest the spread of cholera and liquidate its foci.

[Cholera in the Far East of Russia. Communication 2. Epidemiological characteristics of the outbreak of cholera El tor in Iuzhno-Sakhalinsk]. / Kholera na Dal'nem Vostoke Rossii. Soopshchenie 2. Epidemiologicheskaia kharakteristika vspyshki kholery él'tor v g. Iuzhno-Sakhalinske.

The outbreak of cholera eltor in Yuzhno-Sakhalinsk has been analyzed. The fact of the import of this infection from China and its transmission mainly by the water route due to the intensive contamination of environmental objects has been substantiated. The effective purification decontamination of sewage water plays decisive role on the system of anticholera measures. The conclusion on the necessity of increasing the effectiveness of measures for the sanitary protection of the territory has been made.