S MEISTER¹, M KLINGER¹, T KOHN<sup>1

1</sup>ENAC, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland

Human enteric viruses are a leading cause of waterborne disease outbreak worldwide. Their environmental persistence and resistance to disinfection treatments are two main factors that can influence the dissemination of these viruses, thus increasing the risk of person-to-person transmission. In this study, we isolated and characterized the resistance pattern for several environmental viruses, with the long-term goal of understand the molecular mechanisms underlying resistance and persistence. To obtain environmental isolates, we implemented a method allowing an efficient isolation and concentration of enteric viruses from Lausanne and Minneapolis wastewater treatment plant influents. Single strain viruses were isolated by BGMK cells plaque assay and further characterized by sequencing. In this manner, five Coxsackieviruses B5 (CVB5) and one Coxsackievirus B4 were isolated for further experiments. Several disinfection treatments were used to test the inactivation kinetics of our isolates: UV-C light, Simulated sunlight, Free-chlorine, Chlorine dioxide, and Heat. Their respective inactivation rate constants were measured and compared to CVB5 Faulkner and Echovirus 11 laboratory strains as well as MS2 bacteriophage, a frequently used surrogate. Interestingly MS2 exhibited the most extreme disinfection behaviour, with a low susceptibility for UV-C and sunlight and a high susceptibility for free-chlorine and chlorine dioxide. In contrast, CVB5 isolates shared a more homogenous susceptibility to all disinfectants, though the lab strain was typically less resistant. In addition, a pronounced resistance pattern to chemical disinfectants could be observed in two of our isolates (L3 and L18). This pattern was also observed in heat inactivation experiments, with L3 exhibiting the strongest thermal resistance. In conclusion, we can highlight different resistant patterns even among highly related viruses, possibly due to the high mutation rate of these RNA viruses. In future work, the sequencing of the whole virus genome could help us to understand the molecular mechanisms involved in this resistance, as well as the disinfection cross-resistance observed among our isolates.