ARRS 2022 Abstracts

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ERS2309. Methylene Blue Photodynamic Therapy for Deep Tissue Abscess Sterilization
Authors * Denotes Presenting Author
  1. David Bass *; University of Rochester
  2. Mason Schoeneck; University of Rochester
  3. Ashwani Sharma; University of Rochester
  4. Timothy Baran; University of Rochester
Objective:
Deep tissue abscesses (DTA) are a common problem that present in clinical practice with high morbidity and mortality if left untreated. Current standard of care for treatment includes either surgical washout or percutaneous drainage of the abscess followed by intravenous antibiotics. Failure rates as high as 30% have been reported in some studies, particularly in more complex, loculated collections. As antibiotic resistance continues to grow the non-cure rate of the standard of care may grow. Photodynamic therapy (PDT) had been shown to be effective in sterilizing superficial infections, but little is known on the effectiveness of PDT for DTA. PDT relies on the combination of a light-sensitive drug (photosensitizer), visible light excitation, and molecular oxygen to generate cytotoxic reactive oxygen.

Materials and Methods:
We have initiated a Phase I clinical trial to demonstrate the safety and feasibility of PDT treatment of DTA with the photosensitizer methylene blue (MB). In this trial 1 mg/ml MB is infused into the subject’s abscess cavity after the standard of care percutaneous drainage. MB is allowed to incubate within the cavity for 10 minutes for uptake by any residual microbial population before being aspirated. The cavity is then flushed with sterile saline after which 1% Intralipid is instilled and a sterile optical fiber is centrally placed into the abscess cavity. A laser source then delivers light at 665nm, with a target fluence rate of 20 mW/cm2 at the point on the abscess wall closest to fiber tip. Escalation of illumination duration is being done using a 3+3 design, with a maximum enrollment of 21 subjects.

Results:
We have successfully treated 5 subjects with methylene blue PDT at the time of percutaneous abscess drainage. These have included pelvic, abdominal, and gluteal abscesses, with causes ranging from postoperative infection to intraprostatic abscess. The initial cohort of 3 subjects consisted of in-patients with advanced cancer, while the remaining subjects included out-patients. Even in this challenging patient population, no study-related adverse or serious adverse events were encountered; the procedure was well-tolerated by all subjects. 3 subjects received five minutes of laser illumination, while 2 received 10 minutes of illumination, indicating that preliminary light dose escalation did not increase risk. Additionally, greater than 90% of the methylene blue and Intralipid introduced into patients’ abscesses was successfully aspirated, improving confidence that side effects related to systemic re-distribution of methylene blue and/or Intralipid are unlikely.

Conclusion:
As we continue to investigate the safety and feasibility of methylene blue PDT, it remains promising as a possible adjunct therapy to improve patient outcomes for DTA drainage. PDT could be especially useful in complex loculated abscess that are difficulty to achieve source control in via percutaneous drainage. Current pre-clinical work is focused on using 3D modeling to optimize patient-specific treatment characteristics.