Efficiency of glass wool adsorption-elution technique for the recovery of enteric viruses from water

Abstract

One of the major obstacles to human health relates to unsafe water and poor sanitation. Faecal contamination of source and drinking water introduces enteric pathogens which result in disease outbreaks. Therefore monitoring the occurrence of human pathogens in source water and drinking water is necessary in order to limit the prevalence of environmentally transmitted infectious diseases. Knowledge of pathogen loads in source waters provides the basis for establishing treatment requirements and health standards stipulated by water regulatory authorities and assists in determining the efficacy of water treatment plants. Water quality monitoring and public health assurance is performed routinely by enumerating faecal indicator bacteria. Studies have demonstrated that there is no relationship between current bacterial indicator detection and the presence of enteric pathogenic viruses in treated and source water. There is therefore a need to monitor the levels of pathogenic enteric viruses in surface waters, irrigation water, sewage effluent as well as treated drinking water for public health safety and quality assessment. However due to the low concentration of viruses in water matrices and presence of inhibitors, efficient concentration methods from large quantities of water are essential. The analysis of water for enteric viruses is a two stage process: the first step is to apply efficient viral recovery and concentration procedures from large volumes (10–1000 ℓ) of water followed by viral detection. Glass wool adsorption-elution is a cost-effective and practical viral recovery method for use in resource-limiting settings. The main objective of this study was to determine the efficiency of the glass wool adsorptionelution method for the recovery of viruses of different genera from large water samples (10 ℓ) of different quality by a step-by-step evaluation of its performance using seeding experiments. Standard curves were prepared using quantitative reverse transcription-polymerase chain reactions (RT-PCR)(for RNA viruses) and PCR (for DNA viruses). The efficiency of recovery (EOR) of glass wool between tap water and turbid surface water was compared for six enteric viruses by examining the recovery and loss of viruses at each stage of the process. The generalised linear statistical model was applied to compare the EOR of each virus in each water type and results clearly indicated that the EOR varied for each virus type and was higher for tap water than for turbid surface water for each virus. There was extensive loss of virus in the flow through and this was also higher for the turbid water than the tap water. In this study it was also demonstrated that mengovirus behaved similarly to the pathogenic enteric viruses and was therefore a suitable process control to monitor viral recovery and nucleic acid extraction when recovering and detecting enteric viruses from environmental matrices using glass wool adsorption method. It was also demonstrated that EOR of glass wool for turbid surface water was underestimated as the poor sample quality affected the quantitative molecular detection assays. Adenovirus was shown to be a suitable indicator for virus contamination of water. Modification of the glass wool column preparation did not result in significant difference in EOR but an increase in the amount of glass wool used resulted in reduction in EOR. There were no significant differences between the two polyethylene glycol/sodium chloride (PEG6000/NaCl and PEG8000/NaCl) precipitation methods applied to the secondary concentration of the viruses, but it should be noted that the former has the disadvantage of overnight incubation. The EOR of glass wool was shown to be influenced by pH of the sample. The optimal sample pH for the recovery of hepatitis A virus in turbid surface water was pH 6.0. The study provides valuable new data on the EOR of enteric viruses using the glass wool adsorption-elution technique where virus quantities could be traced from seeding to detection by molecular-based methods.