From Broadband to Single-Tone Stimulation: Frequency-Selective Response of Staphylococcus aureus Biofilms to Electric Fields

Biofilm-associated infections caused by Staphylococcus aureus are highly resistant to antimicrobial treatments. Low-intensity electric fields have shown promise as an antibiofilm strategy; however, the role of frequency remains poorly understood. In this study, mature S. aureus biofilms were exposed to low-intensity alternating electric fields (12.5 mV/cm) across broadband (10 Hz–10 MHz) frequency range and band-limited sub-ranges, as well as to selected single-tone frequencies within the interval 1–100 kHz. Antibiofilm activity was assessed in terms of cell culturability (CFU/mL) and biofilm biomass. A significant frequency-dependent effect was observed (p < 0.001), with maximal activity observed only at specific frequencies within the range 1–100 kHz, whereas other frequencies were ineffective. These findings demonstrate that the electrical antibiofilm effect is characterized by a frequency selective response, which is similar to a band-pass filter with a nearly flat shape inside the band-pass range and strongly attenuated effects outside such a band. This frequency-selective response supports the hypothesis of a biophysical mechanism involving membrane and matrix interactions and highlights the potential for developing targeted, frequency-optimized electroceutical strategies.