Epsilon Archive for Student Projects

Abstract

Frozen, imported raspberries have been linked to several outbreaks of human
norovirus (NoV) gastroenteritis in Sweden. Noroviruses are highly infectious and
are often presented in low numbers in contaminated foods. Detection with RT-PCR
must therefore be preceded by a method that extract and concentrate viruses from
the tested food samples, but most available methods are laborious and/or inefficient.
Studies on noroviruses are further complicated by the fact that human noroviruses
are unable to grow in routinely used cell culture models. The murine norovirus
(MNV), a common pathogen of immunocompromised mice, can be cultivated in
macrophage-like cells and is often used as a model for studies on human
noroviruses.
In the present study, a previously unidentified MNV isolate from Sweden was
sequenced and molecularly characterized. This isolate also served as a surrogate for
testing and further developing a method to concentrate noroviruses from raspberries.
Pathatrix (Life Technologies) is an automated magnet separation system that
allows concentration of viruses or bacteria from large sample volumes. This system
was tested together with cationic paramagnetic beads that attract the negatively
charged surface of NoV particles. Results from this study shows that few modifications
of the Pathatrix protocol might enhance viral recovery. For further evaluation,
the Pathatrix method was compared with polyethylene glycol (PEG) precipitation
for concentrating MNV, NoV GI, and GII from artificially contaminated raspberries.
PEG precipitation was clearly more efficient but displayed a high degree of
inhibition in RT-PCR.
Altogether, this study shows that the Pathatrix method is a convenient and quick
alternative. However, it needs to be further optimized before it can be used to concentrate
noroviruses from raspberries.