Targeting AgrA quorum sensing regulator by bumetanide attenuates virulence in Staphylococcus aureus – A drug repurposing approach

The present study aims to target the quorum sensing (QS) accessory gene regulator A (AgrA) of Staphylococcus aureus to curtail bacterial virulence through drug repurposing approach. In silico screening of chemical ligands that bind specifically to the S. aureus C-LytTR domain of AgrA (AgrAC) was carried out. AgrA inhibition and downregulation of virulence genes linked to QS system of S. aureus were determined. Efficacy, dermal toxicity and drug tolerance induction were tested in Balb/C mice dermonecrosis model. Bumetanide bound to the conserved amino acid Tyr-229 of AgrA and showed 70% AgrA inhibition at 0.1 μM. Highly significant reduction in the expression of representative virulence genes such as alpha-hemolysin (~5 log2-fold), phenol-soluble modulins (~4 log2-fold) and panton-valentine leukocidin (~3 log2-fold) was noted in vitro. In vivo studies signified bumetanide to be highly effective in controlling the ulcer development and promoted wound healing. Also, the tested substance did not have dermal toxicity and no tolerance induction as well. Targeting the QS regulators could be a possible alternative approach to curtail virulence in S. aureus. In addition, if the QS inhibitors are repurposed it could accelerate the drug development process and reduce the cost. The identified drug bumetanide inhibited AgrA and the results were in comparable to that of a known virulence inhibitor, diflunisal. The newly reported results of bumetanide in this study are expected to mark the drug's visibility for antibiotic adjunctive therapy and topical drug formulations for skin infections research. [Display omitted] •Agr quorum sensing pathway regulates virulence in S. aureus.•Repurposing FDA approved drugs as anti-infective can accelerate drug development.•FDA approved drug bumetanide binds to the C-LytTR domain of AgrA of S. aureus.•Significant downregulation of virulence genes such as Hla, PSM and PVL•Effectively controlled tissue ulcer, no dermal toxicity and no tolerance to drug