Staphylococcus aureus (S. aureus) is a human and other animal pathogen that contributes to the primary etiology of
nosocomial pneumonia, a disease with high mortality rates and costs. Treatment of multidrug-resistant S. aureus
infection is extremely challenging, and new therapeutic strategies beyond
antibiotic treatment are needed. Anti-virulence agents that specifically target the molecular determinants of virulence may be a novel method for treating drug-resistant
nosocomial infections.
Sortase B (SrtB) is a crucial
virulence factor in S. aureus and plays an important role during
infection. In this study, we find that
baicalin suppresses the activity of SrtB. Minimum inhibitory concentration and growth curve assays confirmed that
baicalin has no anti-S. aureus properties. We performed live/dead,
lactate dehydrogenase (LDH), adherence, and
enzyme-linked
immunosorbent assays to confirm that
baicalin reduced human alveolar epithelial A549 cell injury caused by S. aureus, reduced the adherence of S. aureus to A549 cells, and significantly attenuated the inflammatory response of mouse macrophage J774 cells to S. aureus. Additionally, we were able to elucidate the binding mechanics and identify the interacting sites of
baicalin and SrtB via a molecular dynamics simulation, site-directed mutagenesis, and fluorescence spectroscopy quenching. Finally, we confirmed that
baicalin directly binds to the active center of SrtB, and the residues Asn92 and Tyr128 perform an important function in the interaction of SrtB and
baicalin. Taken together, these data indicate that
baicalin is a promising candidate to combat S. aureus
infections.