Application of Next-Generation Sequencing to Evaluate the Profile of Noroviruses in Pre- and Post-Depurated Oysters

The development of procedures for the efficient removal or inactivation of noroviruses from contaminated oysters is of great interest in oyster production. However, there is a critical limitation for evaluating the depuration efficacy of presently available procedures, as no suitable cell culture system currently exists to cultivate noroviruses. Thus, we applied a next-generation sequencing (NGS) technique to characterize norovirus genotypes in pre- and post-depurated oysters. As a result, we revealed the diversity of noroviruses in pre- and post-depurated oysters. Although the applied depuration procedure could reduce the number of bacterial agents to the level recommended by the Japanese Ministry of Health, Labour and Welfare, no significant changes were observed in the detection rate and the proportion of norovirus group (G) I and GII genotypes. To our knowledge, this is the first report to evaluate the profile of noroviruses in pre- and post-depurated oysters, specifically with respect to norovirus removal, using NGS; the findings imply that the removal of noroviruses from oysters through depuration is not presently sufficient. Further studies are needed to develop a more suitable depuration procedure for removing and/or inactivating noroviruses from contaminated oysters.