Persistence of enteric virus surrogates in static bacterial biofilms

Background: Norovirus and other enteric viruses are recognized as leading cause of foodborne infections. Fresh produce, meats and ready to eat foods provide an ideal route of transmission for those viruses. Unlike most microbiological agents, viruses cannot replicate on food, therefore contamination levels do not increase during processing or storage and very few viral infectious particles are necessary to induce disease. Enteric viruses are known for their stability in various environments and on surfaces. Also, food processing environments are prime locations for the development of surface-associated microbial communities known as biofilms. It is well known that biofilms contribute to contamination, persistence and hygiene failure in the food industry. Still, relatively little is known about the behavior of foodborne viruses dwelling within these complex communities. The aim of this study was to evaluate the association between enteric viruses and biofilms. Methods: Murine norovirus MNV-1 and rotavirus Wa were used as surrogate and biofilm formation (48h) of mono-culture and mix-cultures (L. plantarum; L. rhamnosus; L. pseudomesenteroides; P. fluoresences) were prepared on 3 surfaces: glass, stainless steel and polystyrene coupons. Viruses were added at final concentration of 105 pfu/ml with each formed biofilm and incubated for 15, 90 min and 24 hrs. Infectious viral particles were detected in biofilms attached at surfaces by plaque assays. Results: An average persistence of 2.4 log/ml of infectious particles of MNV on the 3 surfaces tested without biofilm at all incubation times was observed. No significant association or persistence has been noted between MNV and the mixed biofilm. However, a significant increase of its persistence was detected in presence of simple formed biofilms from the two Lactobacillus used in this study. For rotavirus, the association between the virus and the surfaces without biofilm at 15 min, 90 min, 24 h were shown with a recovery of 2.5, 2.4, and 0.1 log/ml, respectively. However, significant amounts of infectious particles were recovered after 24 hours with some simple and mixed biofilms. These results showed that biofilms can influence the persistence of the rotavirus over time on the glass, stainless steel and polystyrene surfaces. Conclusion: Biofilms on surfaces used in the food industry can influence the presence and persistence of enteric viruses in the environment. However, various factors surrounding this association are unknown and appear to vary depending on viruses and biofilm composition.