In Vitro Inactivation of Respiratory Viruses and Rotavirus by the Oral Probiotic Strain Weissella cibaria CMS1.

Weissella cibaria CMS1 (oraCMS1) has been commercially used in Korea as an oral care probiotic for several years. Human respiratory syncytial virus (RSV) and the influenza A virus (H1N1) are representative viruses that cause infantile lower respiratory tract infections. Rotavirus A (RVA) is the most common cause of diarrhea in infants and young children. Here, we aimed to evaluate the efficacy of the cell-free supernatant (CFS) of oraCMS1 in inactivating RSV, H1N1, and RVA in suspension as per ASTM (American Society for Testing and Materials) E1052-20. The mixture of oraCMS1 and these viruses was evaluated at contact times of 1, 2, and 4 h. Virucidal activity was measured using a 50% tissue culture infective dose assay (logTCID) after infecting the host cells with the viruses. The CFS of oraCMS1 inactivated RSV by up to 99.0% after 1 h and 99.9% after 2 and 4 h, and H1N1 and RVA were inactivated by up to 99.9% and 99.0% at 2 h, respectively. Although these in vitro results cannot be directly interpreted as implying clinical efficacy, our findings suggest that oraCMS1 provides a protective barrier against RSV, H1N1, and RVA, and therefore, it can help decrease the risk of respiratory tract and intestinal infections.