Evidence of the internalization of animal calciviruses via the root of growing strawberry plants and dissemination to the fruit

Food, Agricultural, and Environmental Sciences (FAES): 3rd Place (The Ohio State University Edward F. Hayes Graduate Research Forum)Human norovirus (NoV) is the leading cause of foodborne disease in the U.S. and epidemiological studies have shown that fresh produce is one of the major vehicles for the transmission of human NoV. However, the mechanisms of norovirus contamination and persistence in fresh produce are poorly understood. The objective of this study is to determine whether human NoV surrogates, murine norovirus (MNV-1) and Tulane virus (TV), can attach and become internalized and disseminated in strawberries grown in soil. MNV-1 and TV were inoculated to the soil of growing strawberry plants at a level of 108 PFU/plant. Leaves and berries were harvested over a 14 day period and the viral titer was determined by plaque assay. Over the course of the study, 31.6% of the strawberries contained internalized MNV-1 with an average titer of 0.81 ± 0.33 log10 PFU/g. In comparison, 37.5% of strawberries were positive for infectious TV with an average titer of 1.83 ± 0.22 log10 PFU/g. A higher percentage (78.7%) of strawberries were positive for TV RNA with an average titer 3.15 ± 0.51 log10 RNA copies/g as determined RT-qPCR. In contrast, no or little virus internalization and dissemination was detected when TV was inoculated into bell peppers grown in soil. Collectively, this data demonstrates; (i) virally contaminated soils can lead to the internalization of virus via plant roots and subsequent dissemination to the leaf and fruit portions of growing strawberry plants; and (ii) the magnitude of internalization is dependent on the type of virus and plant.No embarg

Safety of Carrageenan

Carrageenan, a naturally occurring gum derived from red seaweed, is used as a thickener, stabilizer, and emulsifier in food products such as chocolate milk, infant formula, and pie filling. In 2016, because pesticide residues had been discovered in some carrageenan imported from the Philippines, a citizen group that advises the U.S. Department of Agriculture voted to remove carrageenan from a list of foods labeled “USDA Organic.” The controversy surrounding carrageenan is not due to ill health effects caused by carrageenan itself. The U.S. Food and Drug Administration has evaluated carrageenan as “generally recognized as safe.

Leveraging the COVID-19 fermentation trend to enhance nutrition and food safety Extension efforts

Our program aimed to increase knowledge related to fermented foods. Over 400 stakeholders registered for a webinar series that focused on defining fermented foods, health benefits of fermenting foods, and the safety of fermented foods. Participants indicated increases in knowledge and overall satisfaction with the content of the fermentation curriculum. The impact of the COVID-19 pandemic on the program outcomes are discussed

Safety of Carrageenan

Carrageenan, a naturally occurring gum derived from red seaweed, is used as a thickener, stabilizer, and emulsifier in food products such as chocolate milk, infant formula, and pie filling. In 2016, because pesticide residues had been discovered in some carrageenan imported from the Philippines, a citizen group that advises the U.S. Department of Agriculture voted to remove carrageenan from a list of foods labeled “USDA Organic.” The controversy surrounding carrageenan is not due to ill health effects caused by carrageenan itself. The U.S. Food and Drug Administration has evaluated carrageenan as “generally recognized as safe.

Internalization and dissemination of human norovirus and Tulane virus in fresh produce is plant dependent

Human norovirus (NoV) is a leading cause of fresh produce associated outbreaks. Previous research indicates that the roots of growing leafy greens and berries internalize human NoV. However the effect of plant type and inoculum level on internalization rates has not been directly compared. In this study we compared the internalization and dissemination rates of human NoV and its surrogate, Tulane virus (TV) in green onion, radishes, and Romaine lettuce. We also evaluated the effect inoculum level and plant growth matrix on the rate of viral internalization. In the hydroponic growth system, we detected internalization and dissemination of human NoV RNA in green onions. In hydroponically growing green onions inoculated with high titer TV, we found higher rates of internalization and dissemination compared to green onions inoculated with low titer TV. In soil growth systems, no infectious TV was detected in either green onion or radishes. However, in Romaine lettuce plants grown in soil approximately 4 log10 PFU/g was recovered from all tissues on day 14 p.i. Overall, we found that the type of plant, growth matrix, and the inoculum level influences the internalization and dissemination of human NoV and TV

Impact of irrigation water quality on human norovirus surrogate survival during leafy green production

IntroductionThe impact of water quality on the survival of human norovirus (NoV) was determined in irrigation water field run-off (tail water) and well water from a representative Central Coast vegetable production site in the Salinas Valley, California.MethodsTail water, well water, and ultrapure water samples were inoculated separately with two surrogate viruses for human NoV-Tulane virus (TV) and murine norovirus (MNV)-to achieve a titer of 1×105 plaque forming units (PFU)/ml. Samples were stored at 11, 19, and 24°C for 28 days. Additionally, inoculated water was applied to soil collected from a vegetable production site in the Salinas Valley or to the surface of growing romaine lettuce leaves, and virus infectivity was evaluated for 28 days in a growth chamber.ResultsVirus survival was similar for water stored at 11, 19, and 24°C and there was no difference in infectivity based on water quality. After 28 days, a maximum 1.5 log reduction was observed for both TV and MNV. TV decreased by 1.97-2.26 log and MNV decreased by 1.28- 1.48 logs after 28 days in soil; infectivity was not influenced by water type. Infectious TV and MNV were recovered from lettuce surfaces for up to 7 and 10 days after inoculation, respectively. Across the experiments there was no significant impact of water quality on the stability of the human NoV surrogates.DiscussionOverall, the human NoV surrogates were highly stable in water with a less than 1.5 log reduction over 28 days and no difference observed based on the water quality. In soil, the titer of TV declined by approximately 2 logs over 28 days, while MNV declined by 1 log during the same time interval, suggesting surrogate-specific inactivation dynamics in the soil tested in this study. A 5-log reduction in MNV (day 10 post inoculation) and TV (day 14 post inoculation) was observed on lettuce leaves, and the inactivation kinetics were not significantly impacted by the quality of water used. These results suggest that human NoV would be highly stable in water, and the quality of the water (e.g., nutrient content, salinity, and turbidity) does not significantly impact viral infectivity

Thermal Inactivation of Enteric Viruses and Bioaccumulation of Enteric Foodborne Viruses in Live Oysters (Crassostrea virginica)

Human enteric viruses are among the main causative agents of shellfish-associated outbreaks. In this study, the kinetics of viral bioaccumulation in live oysters and the heat stabilities of the predominant enteric viruses were determined both in tissue culture and in oyster tissues. A human norovirus (HuNoV) GII.4 strain, HuNoV surrogates (murine norovirus [MNV-1], Tulane virus [TV]), hepatitis A virus (HAV), and human rotavirus (RV) bioaccumulated to high titers within oyster tissues, with different patterns of bioaccumulation for the different viruses. We tested the thermal stability of each virus at 62, 72, and 80°C in culture medium. The viruses can be ranked from the most heat resistant to the least stable as follows: HAV, RV, TV, MNV-1. In addition, we found that oyster tissues provided protection to the viruses during heat treatment. To decipher the mechanism underlying viral inactivation by heat, purified TV was treated at 80°C for increasing time intervals. It was found that the integrity of the viral capsid was disrupted, whereas viral genomic RNA remained intact. Interestingly, heat treatment leading to complete loss of TV infectivity was not sufficient to completely disrupt the receptor binding activity of TV, as determined by the porcine gastric mucin-magnetic bead binding assay. Similarly, HuNoV virus-like particles (VLPs) and a HuNoV GII.4 strain retained some receptor binding ability following heat treatment. Although foodborne viruses have variable heat stability, 80°C for >6 min was sufficient to completely inactivate enteric viruses in oysters, with the exception of HAV