Inactivation of a Norovirus by High Pressure Processing

Authors: Kingsley, David; HOLLIMAN, DANIEL - VIRGINIA POLYTECHNIC INS.; CALCI, KEVIN - FDA; CHEN, HAIQIANG - UNIV. OF DELAWARE; FLICH, GEORGE - FDA

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2006
Publication Date: 1/1/2007
Citation: Kingsley, D.H., Holliman, D., Calci, K., Chen, H., Flich, G. 2007. Inactivation of a Norovirus by High Pressure Processing. Applied and Environmental Microbiology. 73:581-585.

Interpretive Summary: Human norovirus cannot be cultured in the laboratory or within laboratory animals, however, a mouse virus, called murine norovirus (MNV-1), has recently been discovered that can be propagated in the laboratory. In this study, MNV-1 was used as a research substitute for human norovirus. Results demonstrate that high pressure processing, a commercial process used for oysters and clams, can inactivate this norovirus. Inactivation is enhanced when cooler temperatures, such as 40 degree F, are used instead of room temperature (70 degree F). Extended treatment time of up to 900 seconds at constant pressure demonstrates that while greater time under pressure does yield greater inactivation, the additional incremental increase in inactivation with time is diminishing. To establish the utility of high pressure for sanitization of norovirus-contaminated oysters, MNV-1-contaminated oysters were treated with high pressure. Inactivation of > 99.99% of the virus is demonstrated. This is the first demonstration of pressure inactivation for any norovirus strain and indicates high pressure processing can probably be used as a means of sanitizing shellfish contaminated with human norovirus strains.

Technical Abstract: Murine norovirus (strain MNV-1), a propagable norovirus, was evaluated for susceptibility to high pressure processing. Experiments with virus stocks in DMEM media demonstrated that at room temperature (20 degree C), the virus was inactivated over a pressure range of 350 to 450 MegaPascals (MPa), with a 5-minute 450-MPa treatment being sufficient to inactivate 6.85 log10 PFU of MNV-1. Inactivation of MNV-1 was enhanced when pressure was applied at an initial temperature of 5 degree C; a 5-min pressure treatment of 350 MPa at 30 degree C inactivated 1.15 log10 PFU of virus, while the same treatment at 5 degree C resulted in a reduction of 5.56 log10 PFU. Evaluation of virus inactivation as a function of treatment times ranging from 0 to 150 s and 0 to 900 s at 5 degree C and 20 degree C respectively indicated that a decreasing rate of inactivation with time was consistent with Weibull or log-logistic inactivation kinetics. The inactivation of MNV-1 directly within oyster tissues has been demonstrated where a 5-min 400 MPa treatment at 5 degree C was sufficient to inactivate 4.05 log10 PFU. This work is the first demonstration that norovirus can be inactivated by high pressure and suggests good prospects for inactivation of nonpropagable human norovirus strains in foods.