title: Subinhibitory concentrations of licochalcone A decrease alpha-toxin production in both methicillin-sensitive and methicillin-resistant Staphylococcus aureus isolates.
abstract: OBJECTIVE
  To evaluate the effect of subinhibitory concentrations of licochalcone A (LicA) on alpha-toxin secretion in Staphylococcus aureus.
  
  
  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.
  
  
  CONCLUSIONS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: College of Animal Science and Veterinary Medicine, Jilin University, Changchun 130062, China.
authors.forename: J
authors.initials: J
authors.lastname: Qiu
authors.forename: Y
authors.initials: Y
authors.lastname: Jiang
authors.forename: L
authors.initials: L
authors.lastname: Xia
authors.forename: H
authors.initials: H
authors.lastname: Xiang
authors.forename: H
authors.initials: H
authors.lastname: Feng
authors.forename: S
authors.initials: S
authors.lastname: Pu
authors.forename: N
authors.initials: N
authors.lastname: Huang
authors.forename: L
authors.initials: L
authors.lastname: Yu
authors.forename: X
authors.initials: X
authors.lastname: Deng
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000096:biosynthesis; D047188:Chalcones / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D006460:Hemolysin Proteins / Q000096:biosynthesis / Q000378:metabolism*; D016106:Methicillin Resistance; D011817:Rabbits; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*
chemical_list: D001427:Bacterial Toxins; D047188:Chalcones; D006460:Hemolysin Proteins; C021091:staphylococcal alpha-toxin; C070840:licochalcone A