Low-frequency ultrasound for biofilm disruption in chronic rhinosinusitis with nasal polyposis: in vitro pilot study.

Objectives/hypothesis: Microbial biofilms have been implicated in the pathogenesis of chronic rhinosinusitis with nasal polyposis (CRSwNP). Although biofilms are characterized by an extremely high resistance against chemical and physical agents, low-frequency ultrasound (LFU) treatment has been suspected to be an efficient and safe method for biofilm disruption.

Study Design: Basic science experimental study.

Methods: A total of 10 patients with CRSwNP undergoing endoscopic sinus surgery were analyzed. Two series of identical nasal polyps (n = 20) were processed to hematoxylin-eosin (HE) and Gram staining and to continuous-wave LFU treatment (5 minutes, 0.4 MHz, 37°C), respectively.

Results: Presence of microbial biofilms was confirmed in all patients with CRSwNP. HE staining showed a strong correlation with the results of Gram protocol in biofilm detection. In the LFU-treated group (n = 10), a significantly decreased inflammatory cell count was found in the subepithelial layer of nasal polyps (P < .001). In addition, bacterial biofilms were completely removed from the surface of the epithelial layer. Microscopic tissue injuries or significant temperature changes were not detected due to LFU treatment.

Conclusions: Between in vitro conditions, LFU treatment appeared to be a reliable and microscopically safe method for the disruption of microbial biofilms in CRSwNP. These results may provide a basis for a prospective human study investigating the efficacy and safety of this therapeutic modality alone or in combination with antibiotics or topical steroids in biofilm-positive cases of CRSwNP.