Innovative Methods to Detect Viruses in Food

Because of this increasing number of enteric virus outbreaks, it has become even more important to have reliable and widely applicable techniques for the detection and quantification of viruses in food samples. Moreover, since the infectious dose of enteric viruses is very low, sensitive methods are therefore needed when screening food products for viral pathogens. So far, the current ‘gold standard’ for detection of enteric viruses is quantitative reverse transcription PCR (RT-qPCR) but this method cannot discriminate between infectious and inactivated viruses.The relationship between the number of infectious viruses and the number of genome copies detected by RT-qPCR is not a constant, mainly in food samples, since this ratio may vary depending on environmental conditions.A promising new strategy to assess viral infectivity relies on the use of nucleic acid intercalating dyes, or viability dyes, such as ethidium monoazide (EMA) or propidium monoazide (PMA) as a sample pretreatment before applying molecular techniques. Theoretically, these compounds cannot penetrate intact capsids but are able to penetrate damaged or destroyed capsids. Once penetrated, the dye intercalates covalently into RNA after exposure to strong visible light, interfering with PCR amplification. Until now, viability dyes combined with RT-qPCR have successfully been applied to virus suspensions in order to discriminate between infectious and inactivated viruses. However, the effectiveness of viability dyes to discriminate between infectious and inactivated viruses in food samples has scarcely been explored.