Concentration and detection of caliciviruses from food contact surfaces

Outbreaks of human Norwalk virus (NV) and Norwalk-like viruses often originate in food service establishments. No reliable method is available for the detection of these human caliciviruses on food contact surfaces. We describe a simple method for the detection of NV from stainless steel work surfaces using cultivable feline calicivirus (FCV) as a model. Stainless steel surfaces were artificially contaminated with known amounts of FCV, followed by its elution in a buffer solution. Three methods of virus elution were compared. In the first method, moistened cotton swabs or pieces of nylon filter (IMDS) were used to elute the contaminating virus. The second method consisted of flooding the contaminated surface with eluting buffer, allowing it to stay in contact for 15 min, followed by aspiration of the buffer (aspiration method) after a contact period of 15 min. The third method, the scraping-aspiration method, was similar to the aspiration method, except that the surfaces were scraped with a cell scraper before buffer aspiration. Maximum virus recovery (32 to 71%) was obtained with the scraping-aspiration method using 0.05 M glycine buffer at pH 6.5. Two methods (organic flocculation and filter adsorption elution) were compared to reduce the volume of the eluate recovered from larger surfaces. The organic flocculation method gave an average overall recovery of 55% compared to the filter-adsorption-elution method, which yielded an average recovery of only 8%. The newly developed method was validated for the detection of NV by artificial contamination of 929-cm² stainless steel sheets with NV-positive stool samples and for the detection of the recovered virus by reverse transcription-polymerase chain reaction.