P1-173 Inactivation of GI.6 and GII.4 Human Norovirus by Silver Dihydrogen Citrate

Monday, August 1, 2016
America's Center - St. Louis
Clyde Manuel, North Carolina State University, Raleigh, NC
Matthew Moore, North Carolina State University, Raleigh, NC
Lee-Ann Jaykus, North Carolina State University, Raleigh, NC
Introduction: Human norovirus is the leading cause of viral gastroenteritis worldwide and can remain infectious on surfaces for weeks. Additionally, the virus is resistant to numerous sanitizers and disinfectants. Therefore, there is a need for the development of improved methods for inactivating human norovirus. 

Purpose: The purpose of this study was to investigate the efficacy of a silver dihydrogen citrate (SDC)-containing disinfectant against human norovirus strains GI.6 and GII.4.

Methods: PURE Hard Surface disinfectant (Pure Bioscience, El Cajon, CA) was evaluated using virucidal suspension assays and stainless steel carrier tests according to ASTM International standards. A blend of silver (0.003%) and citric acid (4.846%) in the form of SDC serves as the active ingredients in this product. Inactivation of human norovirus was quantified using RT-qPCR with a prior RNase treatment. Additionally, the impact of SDC against the viral capsid was assessed by transmission electron microscopy, SDS-PAGE/Western blot analysis, and a histo-blood group antigen (HBGA) receptor-binding assay.

Results: Suspension assays showed a 4.0 log reduction in both GI.6 and GII.4 RNA copy number within 5 min exposure. When carriers were used, 30 min of exposure reduced GI.6 and GII.4 RNA concentration by 2.0 and 3.0 log, respectively, indicating human norovirus inoculated onto surfaces was more resistant to SDC than in suspension. Incorporating a soil load into the sample matrix significantly reduced SDC efficacy, which was completely lost for surface-inoculated samples, even after 30 min exposure. Exposure to SDC (30 min) resulted in VLP deformation and aggregation, a 50% reduction in VP1 major capsid protein band intensity, and an 80% reduction in HBGA receptor binding ability.

Significance: These results suggest SDC to work almost exclusively on the capsid of human norovirus. Taken together, the results suggest SDC to be an effective disinfectant for human norovirus when used on pre-cleaned surfaces.