The investigation was concerned with wild gram-positive and gram-negative microorganisms (E. coli spp., Klebsiella spp., Salmonella spp., and the nonfermentative bacteria Pseudomonas spp.) isolated from the waters of different types, as well as museum cultures (E. coli strain 1257, E. coli strain 675, Salmonella enteritidis ATCC 5765, Staphylococcus aureus 906, and Pseudomonas aeruginosa ATCC 10145). The wild strains were isolated from water when conducting experimental and field studies; these are able to survive in the waters disinfected by various procedures (a guanidine-containing disinfectant in non-toxic concentrations; photo-activated decontamination with sensitizers; exposure to magnetic and ultrasound waves). The cytotoxic, adhesive, and invasive activities of the bacteria isolated from environmental water objects increased on their cultivation on nutrient growth media, by simulating their possible effects in man. The developed experimental approach makes it possible to estimate the hazard of potentially pathogenic bacteria in one test trial, by applying the BGM cells and may be used to assess the microbial risk.
The authors have constructed a mathematical model for the cause-and-effect relationship between acute enteric infection (AEI) morbidity and the levels of water bacterial contamination and the properties of microorganisms. New procedures were proposed to calculate a risk for water-borne AEI depending on the sanitary-and hygienic conditions of water use and the degree of water contamination in the direct isolation of the causative agents of pathogenic and opportunistic infections, which allow the calculation and prediction of the occurrence of AEI at the individual and population levels.
The paper estimates the epidemic value of indicators for microbial contamination of waters from their main supply sources (waters from the Tsimlyansk Reservoir and the Nizhni Don River and drinking waters from the towns of Azov and Tsimlyansk) in the Rostov Region. The Tsimlyansk Reservoir water met the SanPiN 220.127.116.110-00 requirements for the normalizable indices of total coliform bacteria (TCB) and thermotolerant coliform bacteria (TtCB) in 54% of the samples; glucose-positive coliform bacteria (GPCB) and Salmonella were isolated in 100 and 60%, respectively. The Azov drinking water that met the SanPiN 18.104.22.1684-01 requirements for TCB and TtCB) was found to contain GPCB, Klebsiella, and Pseudomonas aeruginosa in 5.7, 4.8, and 3% of the samples, respectively Direct detection of pathogenic and potentially pathogenic microorganisms and the integral GPCB index are of the greatest prognostic value in assessing a microbial risk for waterborne enteric infections.
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.
Summary. The paper provides comparative characteristics of water quality in the assessment of a risk for intestinal infections in drinking water use. It has shown that of the greatest predictive value is direct detection of potentially pathogenic microorganisms, as well as the integral indicator determined by glucose fermentation, such as glucose-positive coliform bacteria. Estimation of the per cent of nonstandard samples of water before its entering the distribution network and in the latter, including glucose-positive Escherichia coli GPEC, is recommended. The samples containing GPEC in a quantity of more than 2 CFU/100 ml should be singly taken into account.
Due to intensive anthropogenic pollution of water environment generally accepted indicators of epidemic security of water bodies - common bacteria and thermotolerant coliform bacteria do not always permit to obtain an objective characterization of bacterial contamination of tap water. From the point of view of authors the integral index - glucose positive coliform bacteria most adequately reflect the sanitary-hygienic and epidemiological situation of water bodies. In monitoring for bacterial quality of tap water it is advisable to determine glucose positive coliform bacteria, that will provide the relevance of estimation of the epidemiological safety of water use. According to the method developed by the authors the calculation of the index of population risk of acute intestinal infections occurrence in dependence on the quality of tap water in Azov and Tsimlyansk towns.