Rapid Concentration and Detection Procedure of Enteric Viruses from Berries and Vegetables

Quality & Safety Assurance Department, Nestlé Research Center, Lausanne, Switzerland

^* To whom correspondence should be addressed. Email: gloria.sanchez-moragas{at}rdls.nestle.com.

	Abstract

Several hepatitis A virus (HAV) and norovirus (NV) outbreaks due to consumption of berries and vegetables have been reported during the last years. To facilitate detection of enteric viruses that may be present on different fresh and frozen products, we developed a rapid and sensitive detection method for HAV, NV and rotavirus (RV). Initial experiments focused on optimizing the composition of the elution buffer, improvement of the viral concentration method and evaluation of the performance of various extraction kits. Viruses were extracted from the food surface by a direct elution method in a glycine/Tris pH 9.5 buffer containing 1% beef extract and concentrated by ultrafiltration. Occasionally, PCR inhibitors were present in the processed berry samples, which gave relatively poor detection limits. However, this problem was overcome by adding a pectinase treatment in the protocol, which markedly improved the sensitivity of the method. After optimization, this concentration method was applied in combination with real-time RT-PCR using specific primers in various types of berries and vegetables. The average detection limits were 1 TCID₅₀, 54 PCRU and 0.02 TCID₅₀ per 15 g of food for HAV, NV and RV, respectively. Based on our results it is concluded that this procedure is suitable to detect and quantify enteric viruses within 6 hours and can be applied for surveillance of enteric viruses in fresh and frozen products.