BackgroundBacteria and fungi are believed to influence mucosal inflammation in chronic rhinosinusitis (CRS). However their presence and relationship to disease is debated. This study used multiple detection methods to compare microbial diversity and microbial abundance in healthy and diseased sinonasal mucosa. The utility of contemporary detection methods is also examined.MethodsSinonasal mucosa was analyzed from 38 CRS and 6 controls. Bacterial and fungal analysis was performed using conventional culture, molecular diagnostics (polymerase chain reaction coupled with electrospray ionization time-of-flight mass spectrometry) and fluorescence in situ hybridization.ResultsMicrobes were detected in all samples, including controls, and were often polymicrobial. 33 different bacterial species were detected in CRS, 5 in control patients, with frequent recovery of anaerobes. Staphylococcus aureus and Propionibacterium acnes were the most common organisms in CRS and controls, respectively. Using a model organism, FISH had a sensitivity of 78%, and a specificity of 93%. Many species were detected in both CRS and controls however, microbial abundance was associated with disease manifestation.ConclusionsThis study highlights some cornerstones of microbial variations in healthy and diseased paranasal sinuses. Whilst the healthy sinus is clearly not sterile, it appears prevalence and abundance of organisms is critical in determining disease. Evidence from high-sensitivity techniques, limits the role of fungi in CRS to a small group of patients. Comparison with molecular analysis suggests that the detection threshold of FISH and culture is related to organism abundance and, furthermore, culture tends to select for rapidly growing organisms.
This is the largest study of biofilms in CRS. It has validated mucosal tissue cryopreservation for delayed biofilm analysis. Fungal biofilms have been identified and the importance of S. aureus biofilms in the polymicrobial etiology of CRS is highlighted.
The cell-free fluid (ascitic fluid, AF) of a sterile inflammatory peritoneal exudate elicited in rabbits is potently bactericidal for complement-resistant gram-negative as well as gram-positive bacterial species. This activity is absent in plasma. We now show that essentially all activity in AF against Staphylococcus aureus is attributable to a group II 14-kD phospholipase A2 (PLA2), previously purified from AF in this laboratory. Antistaphylococcal activity of purified PLA2 and of whole AF containing a corresponding amount of PLA2 was comparable and blocked by anti-AF-PLA2 serum. At concentrations present in AF (approximately 10 nM), AF PLA2 kills > 2 logs of 10(6) S. aureus/ml, including methicillin-resistant clinical isolates, and other species of gram-positive bacteria. Human group II PLA2 displays similar bactericidal activity toward S. aureus (LD90 approximately 1-5 nM), whereas 14-kD PLA2 from pig pancreas and snake venom are inactive even at micromolar doses. Bacterial killing by PLA2 requires Ca2+ and catalytic activity and is accompanied by bacterial phospholipolysis and disruption of the bacterial cell membrane and cell wall. These findings reveal that group II extracellular PLA2, the function of which at inflammatory sites has been unclear, is an extraordinarily potent endogenous antibiotic against S. aureus and other gram-positive bacteria.
This study has shown that patients with biofilms have more severe disease preoperatively and persistence of postoperative symptoms, ongoing mucosal inflammation, and infections. This study strengthens the evidence for the role that biofilms may play in recalcitrant CRS.
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