This study aimed to identify
hibifolin as a
sortase A (SrtA) inhibitor and to determine whether it could attenuate the virulence of methicillin-resistant Staphylococcus aureus (MRSA). We employed a fluorescence resonance energy transfer (FRET) assay to screen a library of natural molecules to identify compounds that inhibit SrtA activity. Fluorescence quenching assay and molecular docking were performed to verify the direct binding interaction between SrtA and
hibifolin. The
pneumonia model was established using C57BL/6J mice by MRAS
nasal administration for evaluating the effect of
hibifolin on the pathogenicity of MRSA. Herein, we found that
hibifolin was able to inhibit SrtA activity with an IC50 of 31.20 μg/mL. Further assays showed that the capacity of adhesion of bacteria to the host cells and biofilm formation was decreased in
hibifolin-treated USA300. Results obtained from fluorescence quenching assay and molecular docking indicated that
hibifolin was capable of targeting SrtA
protein directly. This interaction was further confirmed by the finding that the inhibition activities of
hibifolin on mutant SrtA were substantially reduced after mutating the binding sites (TRP-194, ALA-104, THR-180, ARG-197, ASN-114). The in vivo study showed that
hibifolin in combination with
cefotaxime protected mice from USA300
infection-induced
pneumonia, which was more potent than
cefotaxime alone, and no significant cytotoxicity of
hibifolin was observed. Taken together, we identified that
hibifolin attenuated the pathogenicity of S. aureus by directly targeting SrtA, which may be utilized in the future as adjuvant
therapy for S. aureus
infections. IMPORTANCE We identified
hibifolin as a
sortase A (SrtA) inhibitor by screening the natural compounds library, which effectively inhibited the activity of SrtA with an IC50 value of 31.20 μg/mL.
Hibifolin attenuated the pathogenic behavior of Staphylococcus aureus, including adhesion, invasion, and biofilm formation. Binding assays showed that
hibifolin bound to SrtA
protein directly.
Hibifolin improved the survival of
pneumonia induced by S. aureus USA300 in mice and alleviated the pathological damage. Moreover,
hibifolin showed a synergistic antibacterial effect with
cefotaxime in USA300-infected mice.