The pathophysiological role of bacterial biofilms in chronic sinusitis

Chronic rhinosinusitis (CRS) is a very common disorder that remains poorly understood from a pathogenic standpoint. Recent research on the pathogenesis of CRS has been focused on the potential role of biofilms in this chronic infection. The aim of this study was to assess the sinuses’ microflora and biofilm formation on the sino-nasal mucosa in patients with CRS. Paranasal sinus mucosa specimens were harvested at the time of functional endoscopic sinus surgery (FESS). Classical microbiology techniques for the isolation and identification of sinus mucosa microbial flora were used. Scanning electron microscopy (SEM) was used to detect biofilm on the surface of mucosa. A microtiter plate assay for in vitro biofilm formation was employed, divided into three aliquots. One part was assessed for bacterial presence, utilizing an API manual system and the Vitek(®) 2 Compact system. The two remaining aliquots were tested by in vitro conventional microbiological assay with the use of the Infinite M200 (Tecan) microtiter plate reader, and also by scanning electron microscopy (SEM). A microbiological examination of mucosal specimens had taken during FESS operation revealed the presence of various types of bacteria in 29 out of 30 tested samples. Out of 62 different strains isolated from patients with CRS, 23 strains of coagulase-negative Staphylococcus epidermidis and 6 strains of Escherichia coli were the most frequently isolated microorganisms, accounting for 37.1 and 9.7 %, respectively. Among the 62 isolated strains, 58 were used to assess biofilm formation. From the total of 58 isolates, 8.6 % were strong biofilm producers, 20.7 % were moderate, and 70.7 % of isolates were considered to be non- or weak biofilm producers. SEM of the 30 nasal concha mucosal samples taken from patients with CRS revealed biofilm in 23 specimens. A marked destruction of the epithelium was observed, with variation in degrees of severity, from disarrayed cilia to complete absence of cilia. The vast majority of nasal concha mucosal samples of patients affected by chronic sinusitis presented with biofilm formation. Our study showed that 76.7 % of patients having FESS for CRS had evidence of biofilms on SEM micrographs. Although certain detection methods could lead to various discrepancies in the amount of biofilm produced, the consistent demonstration of biofilms in patients with CRS suggests that this convoluted three-dimensional structures might play a significant role in either the pathogenesis or persistence of chronic rhinosinusitis.