Electric fields unlock a transient vulnerability window for vancomycin-based treatment of staphylococcal biofilms

Bacterial biofilms pose a significant challenge to antibiotic treatment. Conventional therapeutic interventions often fail to effectively eradicate mature biofilms due to the protective extracellular matrix and altered physiological states of the embedded bacteria. In this study, we show that low-intensity sinusoidal electric fields induce a time-limited window of vulnerability in mature Staphylococcus aureus biofilms, increasing their susceptibility to vancomycin. In particular, the simultaneous application of electric fields and vancomycin during a transient vulnerability window results in a potentiated effect, leading to an approximately 3-log10 reduction in culturable cell counts relative to untreated controls. Conversely, the effectiveness of the antibiotic is reduced when vancomycin is administered after the cessation of the time-limited vulnerability window associated to the electrical stimulation, indicating a time-dependent reversibility of the electrical effect on the biofilm. These results suggest that the electric fields can create a critical phase of increased susceptibility to antibiotics, establishing a bioelectric strategy for biofilm control and highlighting the importance of treatment timing.