Bacteriophage Monitoring in Drinking Water: Do They Fulfil the Index or Indicator Function?

Abstract

2,187 drinking water samples from various locations in northern part of Israel were tested for bacteriophages presence/absence. Three major groups of bacteriophages were monitored (as related to bacterial host) : Somatic coliphages (host E.coli CN13), F-specific coliphages (host E.coli F+ amp), and Bacteroides fragilis phages (host B.fragilis HSP40). Simultaneously, monitoring of total coliforms and fecal coliforms has been performed. Correlation between bacteriophage group types and the standard water indicators such as coliforms and fecal coliforms was poor. The poor correlation may be attributed to dilution factor (large distance from the pollution source) and/or disinfection process. Presence frequency of the three bacteriophage groups was : 11.5 % somatic coliphages, 6.46 % F-specific coliphages and 5.48 % B.fragilis phages. Bacteriophages' presence plotted against presence of total coliforms, fecal coliforms, or both, revealed that F-specific coliphages and B.fragilis phages are closely related, whereas somatic coliphages group is different. Concentrates of several high volume water samples were tested for enteric viruses and B.fragilis phages presence correlation. All the samples were found negative for both parameters, however positive samples have not been detected. It is expected that continuous monitoring of drinking water for enteric viruses and concurrently for bacteriophages, will elucidate the index potential of bacteriophages. Bacteriophages presence in drinking water points to inadequate water treatment or contamination during the supply practice. Using human specific bacteriophages such as B.fragilis phages, will enable us to differentiate between pollution sources that contaminate drinking water. Future studies should be focused on phages presence as related to health risk assessment, similarly to human pathogens (bacteria, viruses and protozoa). Based on the collected data, F-specific and B.fragilis phages indicate towards reliable future index-organisms of drinking water pollution by sewage.