摘要：Commercial oysters produced in Miyagi Prefecture are randomly selected and tested for noroviruses once per month during the gastroenteritis season from November to March in order to prevent food poisoning. Norovirus genome has been detected by reverse transcription real-time PCR according to the Enforcement Regulation of Food Sanitation Law of Japan (notification method). However, negative samples which were certified according to the positive criterion in the notification method ( i.e. >10 genome copies in each duplicate PCR well) were turned out to be positives by nested real-time PCR, where the partial RdRp-capsid N/S region was pre-amplified by conventional PCR. In this study, 894 commercial individual oysters purchased between November 2011 and March 2015 were tested for noroviruses by real-time PCR, and 256 (28.6%) oysters certified as negatives but with amplification curves ( i.e. <10 genome copies per well) were further investigated by nested real-time PCR. As a result, norovirus genome was detected in 73 (28.5%) individual oysters. Our result suggests that oyster samples which give <10 genome copies per well in real-time PCR should be re-tested by nested real-time PCR.
