MITIGATION OF NOROVIRUS IN OYSTERS USING MICROBIAL AND CHEMICAL STRATEGIES

Abstract

Noroviruses (NoVs) cause gastroenteritis worldwide and can bind to histo-blood group antigens (HBGAs), found in oysters, contributing to NoV bioaccumulation. This thesis explored three strategies to reduce NoV in shellfish: (i) degrading HBGA-like substances with fucosidase-producing bacteria; (ii) blocking NoV by fucoidan; and (iii) inactivating NoVs using photosensitisers. Bifidobacterium bifidum reduced the blocking ability of HBGAs in oyster extracts, but unexpectedly, increased NoV binding and accumulation in oysters. LAB of oysters were screened, and Lactobacillus sakei reduced type A antigenicity but did not significantly reduce NoV in live oysters. Fucoidan was able to protect the cells from Tulane virus (TV, a surrogate for NoVs), but was not able to block the virus, therefore, it cannot be applied to oysters. Finally, photosensitizer Rose Bengal was encapsulated in alginate microbeads and coated with chitosan, resulting in significant reductions of bacteriophage MS2, TV, and Vibrio parahaemolyticus in both in vitro and in vivo.