Internalization and dissemination of human norovirus GII.4 and animal caliciviruses in hydroponically grown Romaine lettuce
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Date
2013-03
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Abstract
Fresh produce is a major vehicle for the transmission of human norovirus (NoV) because it is easily contaminated during both pre- and post-harvest stages however, the ecology of human NoV in fresh produce is poorly understood. In this study, we determined whether human NoV and its surrogates can be internalized via roots and disseminated to edible portions of the plant. The roots of Romaine lettuce growing in hydroponic feed water were inoculated with 1×106RNA copies/ml of human NoV GII.4 strain or 1-2×106PFU/mL of animal caliciviruses (Tulane virus, TV; and murine norovirus, MNV-1), and plants were allowed to grow for 2 weeks. Leaves, shoots, and roots were homogenized and viral titers and/or RNA were determined by plaque assay and/or real-time RT-PCR. For human NoV, high levels of viral genome RNA (105-106 RNA copies/g) were detected in leaves, shoots, and roots at day 1 post-inoculation and remained stable over the 14 day study period. For MNV-1 and TV, relatively low levels of infectious virus particles (101-103 PFU/ml) were detected in leaves and shoots at days 1 and 2 post-inoculation, but reached a peak titer (105-106 PFU/g) at days 3 or 7 post-inoculation. In addition, human NoV had a rate of internalization comparable with TV as determined by real-time RT-PCR. Whereas, TV was more efficiently internalized than MNV-1 as determined by plaque assay. Taken together, these results demonstrated that human NoV and animal caliciviruses attached tightly to roots, became internalized via roots, and efficiently disseminated to the shoots and leaves of the lettuce.
Description
Food, Agricultural, and Environmental Sciences (FAES): 1st Place (The Ohio State University Edward F. Hayes Graduate Research Forum)
Keywords
norovirus, food safety, enteric viruses, fresh produce