Catheter-based Medical Device Biofilm Ablation Using Histotripsy: A Parameter Study

OBJECTIVE: Biofilm formation in medical catheters is a major source of hospital-acquired infections which can produce increased morbidity and mortality for patients. Histotripsy is a non-invasive, non-thermal focused ultrasound therapy and recently has been found to be effective at removal of biofilm from medical catheters. Previously established histotripsy methods for biofilm removal, however, would require several hours of use to effectively treat a full-length medical catheter. Here, we investigate the potential to increase the speed and efficiency with which biofilms can be ablated from catheters using histotripsy. METHODS: Pseudomonas aeruginosa (PA14) biofilms were cultured in in vitro Tygon catheter mimics and treated with histotripsy using a 1 MHz histotripsy transducer and a variety of histotripsy pulsing rates and scanning methods. The improved parameters identified in these studies were then used to explore the bactericidal effect of histotripsy on planktonic PA14 suspended in a catheter mimic. RESULTS: Histotripsy can be used to remove biofilm and kill bacteria at substantially increased speeds compared with previously established methods. Near-complete biofilm removal was achieved at treatment speeds up to 1 cm/s, while a 4.241 log reduction in planktonic bacteria was achieved with 2.4 cm/min treatment. CONCLUSION: These results represent a 500-fold increase in biofilm removal speeds and a 6.2-fold increase in bacterial killing speeds compared with previously published methods. These findings indicate that histotripsy shows promise for the treatment of catheter-associated biofilms and planktonic bacteria in a clinically relevant time frame.