Total flavonoids from Potentilla kleiniana Wight et Arn inhibits biofilm formation and virulence factors production in methicillin-resistant Staphylococcus aureus (MRSA)

Potentilla kleiniana Wight et Arn is a wide-spread wild plant in the mountainous areas in southern China. The whole herb has been used as a traditional herbal medicine to treat fever, arthritis, malaria, insect and snake bites, hepatitis, and traumatic injury. In vitro studies have reported the antibacterial activity use of the plant in traditional medicinal systems.The aim of this study was to investigate the inhibitory activity of total flavonoid from Potentilla kleiniana Wight et Arn (TFP) on methicillin-resistant Staphylococcus aureus (MRSA) in planktonic state and biofilm state.Antibacterial activities of TFP on planktonic MRSA were determined by agar diffusion method, microtiter plate assay and time-kill curve assay. Electrical conductivity, membrane permeability, membrane potential and autoaggregation were analyzed to study TFP effects on planktonic MRSA growth. Crystal violet (CV) staining and confocal laser scanning microscopy (CLSM) were analyzed to study TFP effects on aggregation and maturation of MRSA biofilm. After TFP treatment, extracellular polymeric substances (EPS) production were examined. Morphological changes in planktonic and MRSA biofilm following TFP treatment were determined with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, α-Toxin protein expression and adhesion-related gene expression were also determined.The minimum inhibitory concentration (MIC) of TFP against MRSA was 20 μg/mL. The agar diffusion method and time-kill curve assay results indicated that TFP inhibited planktonic MRSA growth. TFP treatment significantly inhibited planktonic MRSA growth by inhibiting autoaggregation, α-hemolysin activity, α-Toxin protein expression, but increasing electrolyte leakage, membrane permeability and membrane potential and impacting cell structure. Moreover, TFP treatment significantly inhibited aggregation and maturation on MRSA biofilm by decreasing surface hydrophobicity, EPS production and adhesion-related gene expression.The results of this trial provide scientific experimental data on the traditional use of Potentilla Kleiniana Wight et Arn for traumatic injury treatment and further demonstrate the potential of TFP to be developed as a novel anti-biofilm drug.