American Society for Microbiology
Sascha Mormann, Mareike Dabisch, and Barbara Becker
Contaminated food is a significant vehicle of human norovirus transmission. The present study determined the effect of physicochemical treatments on the tenacity of infective human norovirus genogroup II in selected foods. Artificially contaminated produce was subjected to a selection of processes used by the food industry for preservation and by the consumer for storage and preparation. Virus recovery was carried out by ultrafiltration and monitored with bacteriophage MS2 as an internal process control. Norovirus was quantified with monoplex one-step TaqMan real-time RT-PCR and an external standard curve based on recombinant RNA standards. A RNase pretreatment step was introduced to avoid false-positive PCR results caused by accessible RNA allowing the detection of intact virus particles. Significant titer reductions were obtained with heat treatments usually applied by the consumer for food preparation (baking, cooking, roasting). Generally, processes for preservation and storage, such as cooling, freezing, acidification ( pH 4.5) and moderate heat treatments (pasteurization) appear to be insufficient to inactivate norovirus within a food matrix or on the surface. Beside the persistence in processed food, this study provides comparable data about individual matrix-specific protective effects, recovery rates and inhibitory influences on the PCR reactions. The established workflow might be applied to other non-cultivable enteric RNA viruses which are connected to foodborne diseases. The obtained data of this project may also benefit the process optimization for norovirus inactivation in food by adjusting food processing technologies and promote the development of risk assessment systems in order to improve the consumer protection.