An efficient and rapid method for recovery of norovirus from food associated with outbreaks of gastroenteritis

Noroviruses have emerged as the most common cause of foodborne outbreaks of acute nonbacterial gastroenteritis. In this study, two methods for the extraction of viruses from deli ham were compared. Using both methods, as little as 1 to 10 reverse transcription (RT)-PCR units of inoculated norovirus and enterovirus could be detected by nested RT-PCR assays. The fastest and most efficient extraction method based on TRIzol LS Reagent was chosen to identify viruses in food items associated with three different outbreaks. Norovirus was detected using nested (real time) RT-PCR assays that target the genome region routinely used for diagnosis of human cases, thereby facilitating the comparison of sequences detected in food and clinical specimens. For one outbreak, a norovirus sequence (163/163 nucleotides) identical to those detected in clinical samples was found on salami sliced by a food handler with a recent history of gastroenteritis. For the other two outbreaks, norovirus was detected on leftovers of spareribs and ham, but fecal samples from affected persons were not available. The methods used in this study may be useful in future outbreak investigations because the extraction method is easy to perform and suitable for this particular type of food and the detection method facilitates direct comparison of patient and food data.