Usefulness of different groups of bacteriophages as model micro-organisms for evaluating chlorination

Abstract

Aims: To assess the usefulness of bacterial and viral indicators in chlorination processes and to collect quantitative information necessary for risk assessment analysis in water disinfection processes based on chlorination. Methods and Results: Naturally occurring bacterial indicators, bacteriophages and enteroviruses were determined to evaluate the effect of chlorination in groundwater and secondary sewage effluents. Additionally, the effect of chlorinating on selected bacteriophages, enteroviruses and Escherichia coli was also tested in spiked samples of bottled water and sewage effluents. Results indicate that chlorination inactivates more efficiently bacteria than phages and enteroviruses. Among the human viruses, phages infecting Bacteroides fragilis and selected somatic coliphages belonging to the Siphoviridae family were the most persistent to chlorination. Conclusions: The three groups of bacteriophages studied were all more resistant to chlorination than bacteria and some of the phages were more resistant than enteroviruses. Results presented here indicate that it is very risky to generalize from information obtained with inactivation experiments done with single isolates of any phage or virus. If possible, inactivation studies should be done with naturally occurring populations. Phages offer a good opportunity for studying naturally occurring populations. Thus, the bacteriophages offer a range of resistance to chlorination that may represent most of the viruses that can be found in water. Significance and Impact of the Study: Data reported in this study support the inclusion of bacteriophages as additional indicators of the efficiency of water chlorination processes and water quality.

Stability and Infectivity of Cytolethal Distending Toxin Type V Gene-Carrying Bacteriophages in a Water Mesocosm and under Different Inactivation Conditions

“…This may be due to the fact that it is a tailored phage, which has been described as highly stable under different conditions (1,11,20). The results for Cdt phage inactivation were also in agreement with reports on other E. coli phages, either for thermal treatment (8,20,23), UV treatment (20, 31), or chlorination (10,12,26). Chlorinating water with 10 ppm of chlorine would provide water with no bacteria, which would be considered suitable for consumption according to current practices in many parts of the world.…”

“…Cdt-V phages have been detected in fecally polluted wastewater (2), which suggests a certain prevalence of these phages in the environment and reinforces the hypothesis that they mobilize cdt. Therefore, an important aspect to be considered is the survival and persistence of these phages in different environmental conditions, since this will affect the dissemination of cdt genes.Bacteriophages show a higher resistance to natural and anthropogenic external stress factors than bacteria (6,12,20,25,26). Within the different phage groups, it seems that particular morphologies could lead to improved survival of bacteriophages in certain conditions (25,26).…”

“…Bacteriophages show a higher resistance to natural and anthropogenic external stress factors than bacteria (6,12,20,25,26). Within the different phage groups, it seems that particular morphologies could lead to improved survival of bacteriophages in certain conditions (25,26).…”

Persistence of Infectious Shiga Toxin-Encoding Bacteriophages after Disinfection Treatments

“…Samples were treated with 10 ppm of chlorine supplied as sodium hypochlorite and incubated for 1, 3, 5, 10, and 20 min at room temperature (21°C). Residual chlorine was neutralized by adding 3% (wt/vol) sodium thiosulfate (22) before conducting the infectivity and quantification assays.…”

Bacteriophages as Surrogates for the Fate and Transport of Pathogens in Source Water and in Drinking Water Treatment Processes

“… As process indicators phage groups are often successfully employed as enterovirus surrogates in evaluating the effectiveness of water treatment processes and final product quality. This is the case with filtration and disinfection (Stetler et al, 1984;Payment et al, 1985;Havelaar et al, 1993;Durán et al, 2003;Davies-Colley et al, 2005;Persson et al, 2005;Abbaszadegan et al, 2008).  As comprehensive pathogenic virus indices, phages are not very useful.…”