Antiviral activity of yogurt against enterovirus 71 in vero cells

Five yogurts were fermented with each bacteria strain. The viability and pH of each yogurt during fermentation or storage were evaluated, and then the cytotoxicity and antiviral activity against enterovirus (EV) 71 of cell-free supernatants (CFS) of the metabolites of each yogurt were compared with those of de Man, Rogosa, and Sharpe (MRS) broth fermented with the same bacteria. As the results, the number of viable bacteria for each yogurt after fermentation or during storage always remained higher than 5 log CFU/mL and the pH of those ranged from 4 to 6. The CFS of all yogurts showed antiviral activity over 45% against EV71, while it didn't exhibit cytotoxicity in Vero cells. Specially, the CFS of yogurt fermented with Lactobacillus plantarum and Bifidobacterium bifidum exhibited high anti-EV71 activity of 92.74 and 90.44%, respectively. In contrast, the CFS of each MRS broth fermented with the same bacteria showed low antiviral activity of less than 30%.