Subinhibitory concentrations of licochalcone A decrease alpha-toxin production in both methicillin-sensitive and methicillin-resistant Staphylococcus aureus isolates.
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.
Qiu
J
J
College of Animal Science and Veterinary Medicine, Jilin University, Changchun 130062, China.
Jiang
Y
Y
Xia
L
L
Xiang
H
H
Feng
H
H
Pu
S
S
Huang
N
N
Yu
L
L
Deng
X
X
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*
D001427:Bacterial Toxins; D047188:Chalcones; D006460:Hemolysin Proteins; C021091:staphylococcal alpha-toxin; C070840:licochalcone A