Infectivity and nucleic acid persistence of P22 and PP7 virus surrogates in synthetic water matrices under different environmental conditions

Abstract

The persistence of waterborne virus persistence in surface waters may pose a risk to human health. To assess their persistence and mitigate exposure risks in aquatic environments is essential to understand how they (or their surrogates) interact with suspended sediments under different environmental conditions. These sediment particles can adsorb viral particles, influencing their transport, sedimentation, and persistence in aquatic environments. This study evaluated the decay of two virus surrogates, P22 (DNA phage) and PP7 (RNA phage), for enteric DNA and RNA viruses, respectively, in water environments. The phages decay was analyzed using synthetic water matrices with two sediment concentrations (0.5, and 5 g/L), two temperatures (12 and 25 °C), and two electrical conductivities (130 and 1300 μS/cm). Kinetic parameters were calculated using a first-order decay model to estimate phage persistence. Both plaque assays and real-time PCR (qPCR) revealed longer phage persistence at 12 °C than at 25 °C. High sediment concentrations accelerated the decay of both infectious phages and nucleic acids, particularly at 25 °C. High electrical conductivity (1300 μS/cm) exerted a protective effect on PP7 at 25 °C, preserving infectivity and RNA integrity, while it had no impact on P22 persistence. P22 DNA persisted longer than infectious P22, whereas PP7 RNA exhibited similar behavior to infectious PP7. Manual resuspension of sediments resulted in only minor recovery of phages. The results suggest that both sediment and water chemistry must be considered when monitoring enteric viruses in aquatic environments. Additionally, qPCR-based approaches may be useful for studying RNA viruses, especially for viruses that are difficult or impossible to culture, providing complementary information on viral genome stability. However, for DNA viruses, combining culture-based and molecular assays is recommended to better understand decay patterns of both infectious particles and viral genomes. These findings, although limited to virus surrogates in synthetic water matrices, have important implications for designing monitoring strategies to control waterborne viral transmission.