[A comparative study of experimental and commercial serological tests for detection of antibodies in humans with tularemia.]

Experimental serological tests were developed to determine anti-tularensis antibodies in humans in immunochromatography formats (LF-test LPS Ft15) and enzyme immunoassay (ELISA LPS Ft15) using as an antigen highly purified LPS F. tularensis 15 NIIEG. Analysis was conducted of the sensitivity and specificity of the developed tests and commercial tularemia antigen «RNGA-Tul-AG¼ (production Stavropol research anti-plague Institute) in comparison with the commercial reference antigen, registered in the Russian Federation for the quantitative determination of human IgG tularemia - «ELISA classic Francisella tularensis IgG¼ SERION, Germany (IgG SERION ELISA). A study of human blood serum vaccinated against tularemia showed that the sensitivity and specificity of detection of anti-tularemia antibodies by «ELISA LPS Ft15¼ were 97.7 and 100%, compared with «ELISA IgG series¼. When determining antitularemia antibodies with the diagnosis «LF-test LPS Ft15¼, these parameters were compared to «ELISA IgG series¼ 94.3 and 100%. The sensitivity and specificity of «RNGA-Tul-AG¼ made compared to the «IgG ELISA, SERION¼ of 59.1% and 80%.

Chitin and Products of Its Hydrolysis in Vibrio cholerae Ecology.

The role of chitin and its hydrolysis products generated by Vibrio cholerae chitinases in mechanisms of its adaptation in water environments, metabolism, preservation, acquisition of pathogenic potential, and its epidemiological value are reviewed. Chitin utilization by V. cholerae as a source of energy, carbon, and nitrogen is described. Chitin association promotes biofilm formation on natural chitinous surfaces, increasing V. cholerae resistance to adverse factors in ecological niches: the human body and water environments with its inhabitants. Hydrolytic enzymes regulated by the corresponding genes result in complete chitin biodegradation by a chitinolytic catabolic cascade. Consequences of V. cholerae cell and chitin interaction at different hierarchical levels include metabolic and physiological cell reactions such as chemotaxis, cell division, biofilm formation, induction of genetic competence, and commensalic and symbiotic mutual relations with higher organisms, nutrient cycle, pathogenicity for humans, and water organisms that is an example of successful interrelation of bacteria and substratum in the ecology of the microorganism.

[Cholera Vibrio biofilm: production, characterization and role in reservation of causative agent in water environment].

AIM: Experimental production, characterization and evaluation of the role of cholera vibrio biofilm. MATERIALS AND METHODS: 33 strains of Vibrio cholerae eltor O1 and V. cholerae O139 of various epidemic significance and origin were studied in a series of experiments by bacteriologic, microscopic (light-optic, luminescent, scanning electron microscopy), molecular genetics, spectrophotometric and statistical methods. RESULTS: Formation of a biofilm involving inter-cellular bonds, pili and extracellular material and variability of the microorganism (RO-phenotype and transition into uncultivable forms) was shown at various temperature and substrate conditions. A more pronounced ability to form biofilms was detected for strains isolated from environmental samples compared with isolated from clinical material regardless of their epidemic significance. Toxigenic strains of eltor biovar (from surface reservoirs during cholera outbreaks) have demonstrated the highest parameters of optical density compared with toxigenic clinical isolates and non-toxigenic O1 and O139 serogroup cultures. The presence of mbaA1 and mbaA2, vpsR, toxR, hapA genes is common for strains that form a biofilm. CONCLUSION: The data obtained confirm the role of biofilm in reservation of cholera vibrio strains of various epidemic significance in saprophytic phase of microorganism existence.

[MALDI-TOF mass-spectrometric analysis in the accelerated identification of the Vibrio genus microorganisms].

The goal of this work was to develop methodological approaches to identification of the Vibrio genus representatives using the MALDI-TOF mass-spectrometric analysis technologies. The aspects of the biological safety in sample preparations for mass-spectrometric analysis were studied, reference spectra of six typical V. cholerae strains were developed. Identification of 55 strains, representatives of the Vibrio genus, including 45 V. cholerae strains with different epidemic importance, was performed using the MALDI Biotyper 3.0 basis comprising V. cholerae reference spectra. The possibility of reliable definition of the tested strain taxonomic belonging to the species level was demonstrated. Thus, the results completely corresponded to the data of classical microbiological identification. Stability and reproducibility of the offered research method was experimentally shown. The results allow identification of the Vibrio genus representatives to be implemented with the use of the mass-spectrometric analysis as an effective method that defines a species belonging of the basic Vibrio genus representatives in the shortest-terms.

[Molecular-genetic analysis of the epidemical strains of the Vibrio cholerae El Tor isolated from the Siberian and maritime regions of Russia].

The detection of the biotype-specificity, pathogenicity determinants, and sequencing of the ctxB gene and the ctxAB promoter was carried out for analysis of the Vibrio cholerae El Tor strains genome structure. The strains (n = 90) were isolated during cholera epidemic outbreaks in Siberia and the Far East. All toxigenic Vibrio cholerae El Tor strains were divided into two groups: the first group included strains isolated during 1970s: they had the genotype ctxB3+rstREl+rstRCl-rstC+TLC+tbr4. All epidemic dangerous El Tor biotype strains isolated in 1990s belonged to the second group. The strains were characterized as atypical variants because of classical genotype (ctxB1) ctxB gene harboring. The second group fell into three genotypes according to the set of genetic markers (ctxB, rstR, rstC, TLC, tbr). It was suggested that the set of genetic determinants could be used as a marker for epidemiological analysis of spreading of atypical ET strains. The comparative analysis of genome structure enables to suggest possible ways of pathogen evolution.

[Detection of "hybrid" Vibrio cholerae eltor strains during epidemic complications in Syberia and Far East].

AIM: Biotyping of Vibrio cholerae eltor isolated during epidemic complications of cholera in Syberia and Far East by phenotypic and genotypic properties complex. MATERIALS AND METHODS: 45 strains of V. cholerae were studied. Phenotypic analysis was performed by using a complex ofbiovar determining tests. Genotyping was performed by detecting ctxAB, tcpA, toxR, rstRgenes, and ctxB gene structure analysis. RESULTS: All the V. cholerae during epidemiologic complications in Syberia in the 1970s belong to eltor biovar by phenotypic properties and have eltor specific alleles of tcpA and rstR genes, and ctxB of the third genotype in the genome. In the 1990s the strains were phenotypically matching eltor biovar, but had genetical determinants of both eltor(tcpAE1, rstRE1) and classical (ctxB1, rstR(Cl) biovar. CONCLUSION: The cause of epidemic complications of cholera in Syberia in the 1970s was V. cholerae eltor with typical eltor biovarphenotypical and genotypical properties. In the 1990s cases of introduction into the region of "hybrid: V. cholerae eltor strain were ascertained, developing into acute cholera outbreaks in several cases.

[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.