Fruits and vegetables may act as a vehicle of human enteric virus if they are irrigated with sewage-contaminated water or prepared by infected food handlers. An elution-concentration method was modified to efficiently detect, by reverse transcriptase-polymerase chain reaction (RT-PCR) or by cell culture, contamination by poliovirus, hepatitis A virus (HAV), and Norwalk-like virus (NLV) of various fresh and frozen berries and fresh vegetables. The protocol included washing the fruit or vegetable surface with 100 mM Tris-HCl, 50 mM glycine, and 3% beef extract, pH 9.5 buffer, which favors viral elution from acid-releasing berries, supplemented with 50 mM MgCl2 to reduce the decrease in viral infectivity during the process. The viral concentration method was based on polyethylene glycol precipitation. Copurified RT-PCR inhibitors and cytotoxic compounds were removed from viral concentrates by chloroform-butanol extraction. Viruses from 100 g of vegetal products could be recovered in volumes of 3 to 5 ml. Viral RNAs were isolated by a spin column method before molecular detection or concentrates were filtered (0.22-μm porosity) and inoculated on cell culture for infectious virus detection. About 15% of infectious poliovirus and 20% of infectious HAV were recovered from frozen raspberry surfaces. The percentage of viral RNA recovery was estimated by RT-PCR to be about 13% for NLV, 17% for HAV, and 45 to 100% for poliovirus. By this method, poliovirus and HAV RNA were detected on products inoculated with a titer of about 5 × 101 50% tissue culture infectious dose per 100 g. NLV RNA was detected at an initial inoculum of 1.2 × 103 RT-PCR amplifiable units. This method would be useful for the viral analysis of fruits or vegetables during an epidemiological investigation of foodborne diseases.
Modified Concentration Method for the Detection of Enteric Viruses on Fruits and Vegetables by Reverse Transcriptase-Polymerase Chain Reaction or Cell Culture
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ERIC DUBOIS, CÉCILIA AGIER, OUSMANE TRAORÉ, CATHERINE HENNECHART, GHISLAINE MERLE, CATHERINE CRUCIÈRE, HENRI LAVERAN; Modified Concentration Method for the Detection of Enteric Viruses on Fruits and Vegetables by Reverse Transcriptase-Polymerase Chain Reaction or Cell Culture. J Food Prot 1 December 2002; 65 (12): 1962–1969. doi: https://doi.org/10.4315/0362-028X-65.12.1962
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