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.