The efficacy of X-ray doses on murine norovirus-1 (MNV-1) in pure culture, half-shell oyster, salmon sushi, and tuna salad

In this investigation, we determined the efficacy of X-ray doses on reducing a human norovirus (HuNoV) surrogate [murine norovirus-1 (MNV-1)] in pure culture, half-shell oyster, salmon sushi and tuna salad. The pure culture (phosphate-buffer saline, pH 7.4), half-shell oyster, salmon sushi and tuna salad were inoculated with propagated MNV-1 virus stock solution. Half-shell oyster, tuna salad, and salmon sushi samples were then air-dried at 22 °C for 30 min (to allow viral attachment) in the biosafety cabinet and then packaged, separately, in sterilized bags prior to X-ray treatments. Samples were treated with 0.0, 1.0, 2.0, 3.0, 4.0 and 5.0 kGy X-ray. The results of plaque assays demonstrated a high susceptibility of MNV-1 to X-ray treatments. Treatments with 4.0 kGy X-ray achieved the reductions of 3.7 log PFU ml−1 in pure culture or 2.7, 2.2, and 2.0 log PFU g−1 in half-shell oyster, salmon sushi and tuna salad, respectively. Treatment with 5.0 kGy X-ray reduced the MNV-1 from, approximately, 5.5 to 2.9 log PFU g−1 in tuna salad or to below detection limit (<2.0 log PFU g−1) in half-shell oyster and salmon sushi. These results indicated that X-ray is a promising antiviral technology for the seafood industry.