To elucidate the mechanical mechanism by which forsythoside (FOS) combats biofilms of Staphylococcus aureus (including methicillin-resistant Staphylococcus aureus, MRSA), this study determined its minimum inhibitory concentration (MIC). Confocal images were analyzed using CellProfiler to extract structural mechanical parameters. Fluorescence recovery after photobleaching (FRAP) was employed to assess the viscoelasticity (mobile fraction and half-recovery time) of the extracellular polymeric substance (EPS), and a microfluidic platform was used to measure the biofilm detachment rate under fluid shear stress. The results showed that the MICs of FOS against ATCC 25923 and MRSA were 16 and 32 μg/mL, respectively. After treatment with 1×MIC, the biovolume fraction decreased by 52.7%, surface roughness increased by 161.5%, and nearest-neighbor distance increased by 178.9% (all P<0.001). The proportion of dead bacteria (54.7%) and the penetration depth index (PDI, 0.79) were significantly higher than those in the control group. Furthermore, the mobile fraction of EPS increased by 97.3%, the half-recovery time shortened by 53.5% (P<0.001), and the biofilm detachment rate under 2 Pa shear stress (71.6%) was far higher than that of the control group (13.8%). In conclusion, by integrating CellProfiler, FRAP, and microfluidic technology, this study confirmed from a tissue mechanics perspective that FOS disrupts S. aureus biofilms through dual modes of “matrix softening” and “structural embrittlement,” providing systematic mechanical phenotypic evidence for its antibiofilm mechanism.
Li et al. (Wed,) studied this question.