The paper presents the characteristics of microbial communities in the water reservoirs of Eastern Siberia and North and their changes depending on the anthropogenic pollution and analyzes antibiotic resistance in microorganisms. The water contamination with pathogenic viruses was revealed in relation to the man-made load, which may be a criterion for assessing the epidemiological situation on the territories.

In the article results of long-term studying of microbic communities of the largest reservoirs of Eastern Siberia the rivers of Angara, Lena, Selenga, lake Baikal are submitted. It is shown, that in conditions of amplifying anthropogenous influence on an environment there are structural alterations usual microbic communities water objects, the quantity conditional pathogenic gramnegative microorganisms raises, the share antibiotic resistance bacteria is increased.

In the article the results of contamination by viruses of hepatitis A and rotavirus (markers) superficial and underground water sources in large cities of Irkutsk and Chita areas are submitted. Virusological inspection of water objects located in the given territories is shown, that water sources both superficial, and underground type are substantially subject to anthropogenous influence.

The authors of the article analyze morbidity of acute intestinal infections. It has been shown, that distribution of territories by morbidity level of acute intestinal infections of established etiology and by rates of morbidity rise coincides with ranking of these factors by degree of expressiveness of biological properties of pathogens. It is established, that the highest levels of morbidity of acute intestinal infections of established etiology are registered in territories where microorganisms have high resistance to antibiotics, and also tend to increase hemolytic and adhesive activity.

Quantitative relationships were studied between the indicators (common coliform bacteria (CCP), glucose-positive bacteria (GPB), thermoduric bacteria (TDB), coliform bacteria, enterococci, clostridia, coliphages) and the opportunistic (Pseudomonas aeruginosa, Proteus, Klebsiella) and pathogenetic (Salmonella and intestinal viruses) microorganisms at the stages of effluent purification and decontamination, in processes of self-purification in the water reservoirs and of water preparation at water-supplying stations, as well as in the association with the incidence of acute intestinal infections of bacterial and viral genesis in different climatic zones of the country. Salmonella and the opportunistic bacteria of the Enterobacteriaceae family and Pseudomonas aeruginosa were found to be highly resistant to detoxifying agents and environmental factors, adaptable, able to reproduce in pure water, to long survive in underground waters, and to accumulate when water is desalinated at the erections. The cases of intestinal infections were found in the population using the portable water of the standard quality in terms of E. coli, TDB, CCB, and enterococci. In this case only the wider integral index of GPB, which includes the indices of E. coli, TDB, CCB, as well as lactose-negative pathogenic and opportunistic species retains its sanitary significance in terms of all signs and is a reliable indicator of the potential epidemic hazard of drinking water use. Long-term studies have provided evidence for the sanitary value of coliphages as indicators of viral drinking water contamination.

The waters of 25 large rivers falling into the Baikal Lake, their mouth water areas and open Baikal Lake areas to a depth of 500 m were for the first time in the practice of researches on the Baikal Lake were investigated for markers of hepatitis A virus and rotaviruses. The investigations showed an insignificant contamination of surface waters with pathogenic viruses. The antigens of all studied viruses and high values of bacteria from the Escherichia coli group were recorded in the areas exposed to chronic man-made pollution. Data on the seasonal changes in the distribution of enteroviruses indicated their absence in the annual cycle in the pelagic area of the lake, which suggests that viral particle would not accumulate under the conditions of the Baikal Lake over a long period.

As revealed in this study, S. sonnei population is represented by two clusters with respect to the sensitivity to different antibiotics. A higher degree of diversity was observed with respect to the action of streptomycin, kefzol, ampicillin, chloramphenicol and kanamycin in comparison with the action of gentamicin, nevigramon, rafampicin, tetracycline and polymyxin. The level of diversity of S. sonnei with respect to the sensitivity to antibiotics under study underwent essential changes during the calendar year. The distributions obtained study quite closely corresponded to changes in Sonne dysentery morbidity observed within the year period: the first cluster corresponded to the period of morbidity between the seasons and the second one, to the seasonal period of morbidity. The minimal coefficient of diversity fell on May while the maximum--on September. The minimal level of S. sonnei diversity, as a rule, corresponds to the minimum biosystems stability.

The drinking water was tested for viruses in the industrial towns of Eastern Siberia. The findings suggest that extremely poor provision with good quality drinking water is seen in the town of Ust-Ilimsk where there were high levels of pathogenic viruses in the water. The high contamination of drinking water with hepatitis A virus and rotavirus is a cause of higher incidence of intestinal viral infections in the areas under study.