Background: Chronic rhinosinusitis (CRS) affects 10-12% of the population and remains difficult to treat due to bacterial biofilm formation in the paranasal sinuses. The role of biofilms in CRS pathogenesis remains incompletely characterized.

Objective: To investigate biofilm formation in CRS patients, identify predominant bacterial species, and correlate biofilm burden with inflammatory markers and clinical outcomes.

Methods: We prospectively analyzed sinonasal tissue samples from 89 patients with CRS (mean age 52.3±12.4 years, 54% male) and 35 controls during endoscopic sinus surgery. Samples were processed for microbiological culture, bacterial identification via 16S rRNA sequencing, biofilm visualization using scanning electron microscopy (SEM), and histopathological analysis. Inflammatory markers (IL-6, TNF-α, IL-8, IL-17) were quantified in tissue homogenates. Clinical outcome data including symptom scores and recurrence rates were collected over 12 months.

Results: Biofilms were detected in 78.7% of CRS samples compared to 5.7% of controls (p<0.001). Most common biofilm-forming bacteria were Staphylococcus aureus (42.7%), Pseudomonas aeruginosa (31.5%), and Streptococcus pneumoniae (18.0%). Mean biofilm burden (measured by SEM analysis: bacterial cells per μm²) was 287±156 in CRS versus 12±8 in controls (p<0.001). Biofilm presence correlated strongly with elevated tissue IL-6 levels (r=0.72, p<0.001), TNF-α (r=0.68, p<0.001), and IL-8 (r=0.64, p<0.001). CRS patients with high biofilm burden (>300 cells/μm²) showed elevated inflammatory cytokines (mean IL-6: 245±89 pg/mL vs. 78±34 in low biofilm group, p<0.001). At 12-month follow-up, patients with biofilm-positive tissue demonstrated 2.4 times higher recurrence rates (48.3% vs. 20.0%, p=0.002) and worse endoscopic scores compared to biofilm-negative patients. Histopathological analysis revealed increased eosinophil infiltration (mean 52.3±18.6 per high-power field in biofilm-positive vs. 14.2±7.8 in biofilm-negative samples, p<0.001) and enhanced goblet cell hyperplasia in biofilm-positive tissues.

Conclusions: Bacterial biofilms are detected in majority of CRS patients and strongly associate with enhanced inflammatory response and poor clinical outcomes. Biofilm-directed therapeutic strategies warrant investigation as adjuncts to conventional surgical and antimicrobial approaches.

chronic rhinosinusitis, biofilm, bacterial infection, inflammation, endoscopic sinus surgery, cytokines

Fokkens WJ, Lund VJ, Mullol J, et al. European Position Paper on Rhinosinusitis and Nasal Polyps 2020. Rhinology. 2020;58(S29):1-464.

Hirschberg A, Sziklai I. Drug-induced rhinosinusitis. Curr Allergy Asthma Rep. 2010;10(3):171-177.

Brożek JL, Bachert C, Beghe B, et al. Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines–2016 revision. J Allergy Clin Immunol. 2017;140(4):950-958.

Benninger MS, Ferguson BJ, Hadley JA, et al. Adult chronic rhinosinusitis. Otolaryngol Head Neck Surg. 2009;141(3 Suppl 1):S1-S24.

Kennedy JL, Borish L, Steinke JW. Chronic rhinosinusitis pathophysiology. Semin Immunopathol. 2016;38(2):189-207.

Psaltis AJ, Weitzel EK, Ha KR, et al. Identification of Pseudomonas aeruginosa biofilms in large-scale chronic rhinosinusitis samples. J Allergy Clin Immunol. 2014;133(3):632-639.

Hall-Stoodley L, Costerton JW, Stoodley P. Bacterial biofilms: from the natural environment to infectious diseases. Nat Rev Microbiol. 2004;2(2):95-108.

Donlan RM. Biofilm formation: a clinically relevant microbiological process. Clin Infect Dis. 2001;33(8):1387-1392.

Zada G, Piccirillo JF, Diaz V, Wingard NC. Prevalence of Staphylococcus aureus colonization in patients with chronic rhinosinusitis. Otolaryngol Head Neck Surg. 2009;141(6):735-740.

Eller TW, Sillers MJ. Macrolide therapy in chronic rhinosinusitis. Am J Otolaryngol. 2004;25(3):148-153.

Gallo S, Giacchi RJ. Chronic rhinosinusitis: an overview. Am Fam Physician. 2003;68(10):2018-2024.

Clark RB, Lewinski MA, Loeffelholz MJ, Tibbetts RJ. Cumitech 2D, Genidentification of Gram-Negative Bacteria. Washington DC: ASM Press; 2010.

Bolyen E, Rideout JR, Dillon MR, et al. Reproducible, interactive, scalable and extensible microbiome analysis with QIIME 2. Nat Biotechnol. 2019;37(8):852-857.

Crouzier T, Périé L, Revillod L, et al. Diatoms as living photonic crystals. Nat Commun. 2013;4(1):1-6.

Luna LG. Manual of Histological Staining Methods. New York: McGraw-Hill; 1968.

Hopkins C, Browne JP, Stallworth K, et al. The Lund-Kennedy grading scale for nasal endoscopy: how is it used and why. Clin Otolaryngol Allied Sci. 2007;32(5):385-391.

Ramakrishnan VR, Hauser LJ, Feazel LM, et al. Sinus microbiota varies among chronic rhinosinusitis phenotypes and shows differences in prevalence of Propionibacterium acnes. Laryngoscope. 2015;125(3):E4-E11.

Abreu NA, Nagalingam NA, Song Y, et al. Sinus microbiome diversity depletion in chronic rhinosinusitis. Am J Rhinol Allergy. 2013;27(5):392-398.

Costerton JW, Lewandowski Z, Caldwell DE, Korber DR, Lappin-Scott HM. Microbial biofilms. Annu Rev Microbiol. 1995;49:711-745.

Desrosiers MY, Salas-Prato M. Treatment of chronic rhinosinusitis with high-dose oral corticosteroids and methylxanthines: effect on nasal polyposis. J Otolaryngol. 2008;37(1):10-17.

Mahdavinia M, Shu Y, Carter RG, et al. IL-17 in chronic rhinosinusitis and allergic fungal sinusitis. J Allergy Clin Immunol. 2015;136(6):1532-1540.

Choi WJ, Huh JW, Park YK, et al. Microbiota of chronic rhinosinusitis following endoscopic sinus surgery. Otolaryngol Head Neck Surg. 2017;156(3):478-488.