The persistence of viruses in biofilms from water distribution systems

This research aimed to investigate whether water distribution system biofilms could act as a potential reservoir for viruses. Model water distribution systems were set up in the laboratory and biofilm formation was monitored. Two model viruses, bacteriophage lambda and poliovirus, were introduced into the system and their interactions with the two phases of the biofilm model (planktonic and sessile) were followed over a period of time using molecular detection methods and traditional culture procedures. In the planktonic phase both viruses decreased in number eventually disappearing, while in the sessile phase some viral adsorption was initially apparent but this too disappeared with time. In some cases the virus persisted in the sessile phase for longer than it did in the planktonic phase but this was not reproduced consistently. Enumeration of virus showed no correlation between viral numbers in the two phases indicating that much of the virus was being destroyed or inactivated by the biofilm. The similar patterns observed for both viruses showed that this was a non-specific reaction by the biofilm and observations of virus in biofilm leachate alone suggested the biofilm matrix or its continual production of leachate was responsible. Molecular methods, as distinct from culture methods, revealed that poliovirus remained present in the model for the entire duration of every experiment. This suggested that the detrimental actions of the biofilm either caused virus inactivation or promoted its physical destruction to levels lower than the detection limits of the traditional culture methods.