Author's personal copy Are Biofilms the Answer in the Pathophysiology and Treatment of Chronic Rhinosinusitis? Shaun J. Kilty, MD a , MartinY. Desrosiers, MD b,c, * Although the discovery of a bacterial biofilm is centuries old, it was not until recently that evidence for bacterial biofilm formation and control was found. 1–3 Since then, there has been an intensive development of scientific knowledge of biofilm growth, behavior, and therapy. In otolaryngology, a great deal of knowledge has developed implicating bacterial biofilms in recurrent adenotonsillar infection, otitis media, choles- teatoma, and chronic rhinosinusitis (CRS). 4,5 To date, rhinologic research on biofilm disease in CRS suggests that biofilms may significantly contribute to the chronic inflammation that is characteristic of this disease. How central a role they play remains the subject of debate. WHAT IS A BIOFILM? A biofilm is an organized community of bacteria adherent to a mucosal surface or foreign body, situated in an extensive extracellular polymeric substance (EPS, or gly- cocalyx) composed primarily of polysaccharides, but also containing protein and a Department of Otolaryngology- Head and Neck Surgery, University of Ottawa, Ottawa Hospital, Civic Campus, 1053 Carling Avenue, Ottawa, Ontario K1Y 4E9, Canada b Department of Otolaryngology, Ho ˆ pital Ho ˆ tel-Dieu, Pavillon Ho ˆ tel-Dieu, Universit e de Montr eal, 3840, rue St Urbain, Montreal, Quebec H2W 1T8, Canada c Department of Otolaryngology, McGill University, 687 Pine Avenue West Montreal, Quebec H3A 1A1, Canada * Corresponding author. Department of Otolaryngology, Pavillon Ho ˆ tel-Dieu, 3840, rue St Urbain, Montreal, QC H2W 1T8, Canada. E-mail address: desrosiers_martin@hotmail.com (M.Y. Desrosiers). KEYWORDS  Biofilms  Chronic sinusitis  Endoscopic sinus surgery  Staphylococcus aureus  Pseudomonas aeruginosa  Coagulase-negative staphylococci  Haemophilus influenzae  Biofilm therapy Immunol Allergy Clin N Am 29 (2009) 645–656 doi:10.1016/j.iac.2009.07.005 immunology.theclinics.com 0889-8561/09/$ – see front matter ª 2009 Elsevier Inc. All rights reserved.