Submitted to: Applied and Environmental Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/15/2014
Publication Date: 4/1/2014
Citation: Ye, M., Li, X., Kingsley, D.H., Jiang, X., Chen, H. 2014. Inactivation of human norovirus in contaminated oysters and clams by high-hydrostatic pressure. Applied and Environmental Microbiology. 80:2248-2253. Interpretive Summary: The Porcine Gastric Mucin (PGM) binding assay has been developed to assess inactivation of human norovirus. In this publication, it is applied to high pressure-treated oysters and clams to analyze and compare the inactivation of GII.4 and G1.1 human norovirus strains by high pressure processing, a nonthermal intervention technique for raw shellfish. We show that the more common strain (GII.4) is more sensitive to high pressure processing, and demonstrate that the novel assay can be applied to shellfish samples. We also characterize the inactivation profile of two strains of human norovirus within a shellfish matrix.
Technical Abstract: Human norovirus (NoV) is the most frequent causative agent of foodborne disease associated with shellfish consumption. In this study, the effect of high-hydrostatic pressure (HHP) on inactivation of NoV was determined. Genogroup I.1 (GI.1) or Genogroup II.4 (GII.4) NoV were inoculated into oyster homogenates and treated at 300 to 600 MPa at 25, 6 and 1 degrees C for 5 min. After HHP, samples were treated with RNase and viral particles were extracted by porcine gastric mucin (PGM)-conjugated magnetic beads (PGM-MBs). Viral RNA was then quantified by real-time RT-PCR. Since PGM contains histo-blood group-like antigens which can act as receptors for NoV, deficiency for binding to PGM is an indication of loss of infectivity of NoV. After binding to PGM-MBs, RT-PCR detectable NoV RNA in oysters was reduced from 0.4 to greaer than 4 log by HHP at 300 to 600 MPa. The GI.1 NoV was more resistant to HHP than the GII.4. HHP at lower temperatures significantly enhanced the inactivation of NoV in oysters. Pressure treatment was also conducted for clam homogenates. Treatment at 450 MPa at 1 degree C achieved a greater than 4 log reduction of GI.1 NoV in both oyster and clam homogenates. It is therefore concluded that HHP could be applied as a potential intervention for inactivating NoV in raw shellfish. The method of pretreatment of samples with RNase, extraction of viral particles using PGM-MB binding, and quantification of viral RNA using RT-PCR can be explored as a practical means of distinguishing between infectious and non-infectious NoV.