Enhancement of norovirus detection rates in oysters and other food samples by using bacterial treatment

Abstract

Factors such as low recovery rate and food contaminants may be responsible for the difficulty of detecting Norovirus (NV) by PCR in foodborne outbreaks. To detect NV more efficiently, we introduced a bacterial treatment, in which concentrated samples were incubated overnight with Klebsiella oxytoca at 35°C before RNA extraction using the standard protocol. Recovery rates of NVs (G I/8 or G II/13) added to food suspensions in the modified method were compared with those in the standard method by quantification of NV RNAs using real-time PCR. Recovery rates in the modified method were 8.6% for GI/8 and 11.6% for GII/13 in 18 oyster samples and 13.9% for GI/8 and 19.6% for GII/13 in 15 other food samples, while those in the standard method were 0.3% for GI/8 and 0.5% for GII/13 in the oyster samples and 1.9% for GI/8 and 7.9% for GII/13 in the other food samples. These results indicate that the bacterial treatment increase the recovery of NV from foods such as oysters, suggesting that the modified method will be useful for NV detection in food samples.