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P2-44 Enteric Virus Survival on Alfalfa Seeds and Sprouts

Tuesday, July 24, 2012
Exhibit Hall (Rhode Island Convention Center)
Qing Wang, University of Delaware, Elkton, MD
Kirsten Hirneisen, University of Delaware, Newark, DE
Sarah Markland, University of Delaware, Wilmington, DE
Kalmia Kniel, University of Delaware, Newark, DE
Introduction: In addition to the numerous outbreaks of foodborne illness associated with alfalfa sprouts, the recent outbreak of E. coli O104:H4 in fenugreek seeds increased awareness for seed and sprout safety. Studies focused on understanding the interaction of pathogens with seeds and prevention have focused on bacterial pathogens; however, enteric viruses cause over 5 million illnesses each year in the US and are a concern for produce contamination via contaminated water or infected food handlers.  Human norovirus and hepatitis A virus are the most common causes of foodborne illness by enteric viruses. Using alfalfa seeds as a model, the interaction and survival of enteric viruses was assessed.  

Purpose: The objective of this study was to determine the persistence of enteric viruses on alfalfa seeds during prolonged seed storage and to determine the risk associated with contaminated seeds during germination in sprouts and germination water.

Methods: Alfalfa seeds were sterilized and inoculated with human norovirus surrogates (murine norovirus (MNV) and Tulane virus (TV)) and hepatitis A virus (HAV). Seeds were stored for 20 days at 22 °C and sampled every 5 days.  Seeds were analyzed for virus presence using quantitative RT-PCR and infectivity assays. Seeds were germinated and virus presence was assessed on sprouts and in germination wastewater. Virus survival in HBSS served as a positive control and the negative control was non-inoculated alfalfa seeds.

Results: MNV titer on alfalfa seeds decreased over 20 days from 7.05 ± 0.50 log PFU/g on day 0 to 1.30 ± 1.84 log PFU/g. HAV and TV persisted on seeds over the course of 20 days with similar reductions in titer to MNV.  MNV and HAV were detected in water used to germinate the seeds at 2.39 ± 0.56 log PFU/ml and 3.75 ± 0.84 log TCID50/ml, respectively. Viruses were found to be present on sprouts after germination.

Significance: Enteric viruses persisted on alfalfa seeds prior to sprouting and pose a threat for contamination of sprouts during germination.

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