Antibacterial and Antibiofilm Activity of Clerodendron Cyrtophyllum Turcz. Ethanolic Extracts against Staphylococcus aureus from Bovine Mastitis.

Bovine mastitis causes huge economic losses for the dairy industry worldwide. Staphylococcus aureus (S. aureus) is an important pathogen that induces bovine mastitis, and its resistance to antibiotics has become a severe problem in bovine mastitis therapy. Therefore, the development of new treatments for this potentially fatal infection is urgently needed. Clerodendron cyrtophyllum Turcz. is a traditional Chinese medicine that has been used for the treatment of various diseases. However, its antibacterial effect on S. aureus in bovine mastitis is rarely investigated. In this study, Clerodendron cyrtophyllum ethanolic extract (CTE) was prepared, and its S. aureus-inhibting activities and antibiofilm effects were determined. The mechanisms of CTE against S. aureus were also investigated. The results showed that the growth of S. aureus was inhibited by CTE, and the minimum inhibitory concentration (MIC) of CTE was 250 μg/ml. After treatment with CTE, extracellular alkaline phosphatase (AKP), protein, and nucleic acid of S. aureus were increased, suggesting that the permeability of S. aureus cells was enhanced. Furthermore, intracellular reactive oxygen species (ROS) in S. aureus were increased, suggesting that CTE inhibited S. aureus growth by causing oxidative damage. In addition, CTE treatment suppresses biofilm formation of S. aureus, as almost 50% of biofilm was scavenged at 2× (MIC) of CTE. After CTE treatment, icaA, sarA, and sigB mRNA levels were significantly downregulated, whereas the icaR mRNA level was significantly upregulated, indicating that CTE suppressed biofilm formation by regulating expression of the biofilm formation-related genes. The findings of this study indicate that CTE could be a potential treatment for bovine mastitis-associated S. aureus.