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 di$culty of detecting Norovirus (NV) by PCR in foodborne outbreaks. To detect NV more e$ciently, we introduced a bacterial treatment, in which concentrated samples were incubated overnight with Klebsiella oxytoca at 35ῒ 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 8.6ΐ for G I/8 and 11.6ΐ for G II/13 in 18 oyster samples and 13.9ΐ for G I/8 and 19.6ΐ for G II/13 in 15 other food samples, while those in the standard method were 0.3ΐ for G I/8 and 0.5ΐ for G II/13 in the oyster samples and 1.9ΐ for G I/8 and 7.9ΐ for G II/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.

Detection of norovirus in food samples collected during suspected food‐handler‐involved foodborne outbreaks in Tokyo

“…To clarify the source of infection in serial outbreaks of food poisoning affecting 1193 individuals in Tokyo in February 2017, sample pretreatment with the bacterial culture method was useful to detect NoV in shredded dried laver seaweed (Somura et al ). Although the mechanism underlying the contribution of bacteria in increasing viral recovery rates and obliterating PCR inhibitors is yet unclear, the combined use of the bacterial culture method and ultracentrifugation increases the NoV recovery rate in comparison with ultracentrifugation alone (Akiba et al ).…”