Synergistic Antibacterial Effect of Lactic Acid Bacteria and Baicalin Against Staphylococcus aureus In Vitro and In Vivo.

Abstract

Pathogenic bacteria such as Staphylococcus aureus (S. aureus) are the principal cause of cow mastitis, which primarily impacts milk yield and results in significant financial losses for the animal husbandry industry. Lactic acid bacteria-cell-free supernatant (LAB-CFS) and baicalin (BAI) both have a number of biological effects, including decreasing inflammation. The combined use of LAB-CFS and BAI does not appear to have been used to protective against mastitis, however, and the underlying mechanisms are yet unknown. In this study, in vitro activity of LAB-CFS and BAI alone and in combination was determined (checkerboard experiments, time-kill curves, and flow cytometry to investigate membrane permeability) and examined the protective effects of LAB-CFS and BAI on S. aureus-induced mastitis in mice and the impact of NF-κB signaling pathways on the emergence of mastitis. We discovered that when LAB-CFS and BAI were used together, S. aureus was more effectively treated than when LAB-CFS and BAI were used separately. Flow cytometry demonstrated that LAB-CFS and BAI work together to kill bacteria. In vivo, the usage of LAB-CFS and BAI decreased the activity of myeloperoxidase, as well as IL-6, IL-1β, and TNF-α secretion and the levels of TLR2 and p65 (NF-κB) expression. These findings suggested that LAB-CFS and BAI had a preventive effect against mastitis brought on by S. aureus. Therefore, the NF-κB signaling pathway is thought to be the likely mechanism through which LAB-CFS and BAI reduced S. aureus-induced inflammation in the mammary of cows. For the treatment of cow mastitis, LAB-CFS and BAI are likely to replace antibiotics.