23. The Effects of Low Frequency Ultrasound on Pseudomonas aeruginosa Pathogenicity Factors

Abstract

Pseudomonas aeruginosa is a common bacterium found in wound infections and is becoming increasingly difficult to treat. P. aeruginosa is naturally resistant to many antibiotics due to several factors including its efflux pumps as well as the alginate matrix surrounding each cell. This species is also known to form biofilms which increases its resistance to antibiotics and can be problematic in antimicrobial chemotherapy and wound care. Low frequency ultrasound (LFU) wound irrigation devices (35 kHz) convert electrical energy into mechanical energy via resonance while using sterile saline as the transduction medium. Previous work has shown that these devices can cause mechanical cell death of pathogens such as Staphylococcus aureus. Due to these findings, exposing P. aeruginosa to the energy from an LFU wound irrigation device may also make them more susceptible to antibiotics including aztreonam, cefepime, and gentamicin, which are specifically used in the treatment of P. aeruginosa infections. In our work, exposure to the ultrasound energy resulted in a gradation of cell death and increased susceptibility to the previously mentioned antibiotics. Out of five time exposures, 15 second intervals (15-75 seconds), we observed a constant increase in antibiotic susceptibility and cell death. Seventy-five second exposure yielded the highest kill rate as well as the largest zones of inhibition. These results provide a theoretical framework that could be employed in future treatment of P. aeruginosa infections by decreasing antibiotic resistance and reducing treatment duration.