P-057. Persistence of Representative Members of the Norovirus Genus on Foods and Food Contact Surfaces
Noroviruses (NoV), a genus within the Caliciviridae family, are significant agents of acute non-bacterial gastroenteritis worldwide Despite numerous efforts to cultivate the human NoV, they remain difficult using readily available mammalian cell culture models. The murine norovirus (MNV-1) has been used as a relevant surrogate. It belongs to the NoV genus and appears to have similar molecular and biological characteristics to human strains. In this study, was evaluated the persistence of representative NoVs on common food contact surfaces (stainless steel, ceramic, and Formica®) and food (lettuce) using a combination of quantitative real-time (qRT-PCR) and cell culture infectivity. Based on detection of viral RNA using qRT-PCR, the concentration of genogroup I (GI) and II (GII) human NoV on surfaces dropped gradually over time with an average reduction of 1.5-2.0 log10 and 1.8-2.3 log10,, respectively after 45 days. There were no significant differences when comparing virus behavior on different surfaces. Similar experiments were done on inoculated lettuce stored for 2 weeks at 4 and 21 C. In this case, virus titer was reduced over 2 weeks by a maximum of 1.2 and 0.9 log10 for GI and GII NoV, respectively, when lettuce was stored at 4 C. At room temperature, log reductions were 1.8 and 1.2 log10, respectively. When purified viral RNA was placed on surfaces or lettuce, qRT-PCR signal was lost in < 7 days, suggesting that at least some of the quantifiable RNA detected after day 7 was associated with infectious virus. When similar experiments were done with MNV-1, there was relatively poor correlation between qRT-PCR and infectivity assay results. Specifically, virus infectivity was lost rapidly (within 7 days), whereas virus remained detectable by qRT-PCR for up to 45 days. Interestingly, in this case, purified viral RNA was stable for long periods of time (21 and 14 days for surfaces and lettuce, respectively). While these data support the well accepted notion that qRT-PCR detection is not indicative of infectious virus, differences between the MNV-1 and human NoV findings may call into question the relevance of MNV-1 as a surrogate for human strains in environmental persistence studies.