Investigation of norovirus contamination in commercial oysters in Beijing

Abstract

Objective To investigate the contamination of norovirus in oysters sold in Beijing and to analyze the molecular characteristics. Methods From February, 2014 to March, 2015, 56 samples were collected from a seafood market in Beijing. Each sample was consisted of 5 oysters, totally 280 oysters. Norovirus nucleic acid was detected by Real-time RT-PCR. Norovirus capsid protein region was amplified by semi-nested RT-PCR from positive specimens. PCR products were sequenced directly. BioEdit 7.0.9.0 software was used for sequence alignment, and MEGA 6.06 software was used to construct the phylogenetic tree. Results The detection rate of norovirus was 37.50% (21/56), including twenty strains of genogroup GII and one mixture strain of genogroups GI and GII. The detection rate of norovirus was the highest in winter (75.00%, 15/20), followed by autumn (3/12) and spring (3/16), and no detection in summer. Six norovirus-positive samples were successfully sequenced. Four GII.17 strains, one GII.3 strains, and one mixture strain of GII.18 and GII.4 Sydney 2012 strain were identified. Conclusions Norovirus contamination existed in some oysters sold in Beijing, indicating a risk of foodborne illness. Key words: Oyster; Norovirus; Semi-nested RT-PCR; Genotype