Aim: To evaluate the effect of subinhibitory concentrations of licochalcone A (LicA) on alpha‐toxin secretion in Staphylococcus aureus.
Methods and Results: A haemolysin assay was used to investigate the haemolytic activities in culture supernatants of both methicillin‐sensitive and methicillin‐resistant Staph. aureus isolates cultured with graded subinhibitory concentrations of LicA. Alpha‐toxin secretion was detected by immunoblot analysis. Moreover, quantitative RT‐PCR was performed to assess the influence of LicA on the transcription of hla (the gene encoding alpha‐toxin) and agr (accessory gene regulator). Growth in the presence of LicA markedly inhibited the mRNA levels of hla and agr in Staph. aureus, resulting in a reduction of alpha‐toxin secretion and, thus, haemolytic activities.
Conclusion: The secretion of alpha‐toxin in Staph. aureus is decreased by LicA; this effect may be partially dependent upon inhibition of the Agr two‐component system.
Significance and Impact of the Study: The findings in our study may support the use of LicA as a lead compound in the design of more potent antibacterial agents that are based on the chalcone template.