Аннотации:
Bacterial biofilms are typically more tolerant to antimicrobials compared to bacteria in the
planktonic phase and therefore require alternative treatment approaches. Mechanical
biofilm disruption from ultrasound may be such an alternative by circumventing
rapid biofilm adaptation to antimicrobial agents. Although ultrasound facilitates biofilm
dispersal and may enhance the effectiveness of antimicrobial agents, the resulting
biological response of bacteria within the biofilms remains poorly understood. To
address this question, we investigated the microstructural effects of Pseudomonas
aeruginosa biofilms exposed to high intensity focused ultrasound (HIFU) at different
acoustic pressures and the subsequent biological response. Confocal microscopy
images indicated a clear microstructural response at peak negative pressures equal
to or greater than 3.5 MPa. In this pressure amplitude range, HIFU partially reduced
the biomass of cells and eroded exopolysaccharides from the biofilm. These pressures
also elicited a biological response; we observed an increase in a biomarker for biofilm
development (cyclic-di-GMP) proportional to ultrasound induced biofilm removal. Cyclicdi-GMP overproducing mutant strains were also more resilient to disruption from HIFU
at these pressures. The biological response was further evidenced by an increase in
the relative abundance of cyclic-di-GMP overproducing variants present in the biofilm
after exposure to HIFU. Our results, therefore, suggest that both physical and biological
effects of ultrasound on bacterial biofilms must be considered in future studies.