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Thursday, March 13, 2014

Host-microbial interactions in patients with chronic rhinosinusitis

The initiation and perpetuation of chronic rhinosinusitis (CRS) is known to be associated with host-microbial interactions.  Many studies have investigated these interactions with CRS in order to understand the mechanisms of the disease and provide better treatment options.  Dr. Hamilos summarizes the knowledge of host-microbial interactions in regards to normal sinus physiology and pathology, patients with CRS with and without polyps, and allergic fungal rhinosinusitis (AFRS) (J Allergy Clin Immunol 2014; 133(3): 640-653).
Much of the research on the subject of CRS has been on bacterial infection and potential defects in innate immunity that might predispose patients to sinus infections.  Of CRS patients undergoing surgical intervention, more than 50% have bacterial biofilm in their diseased sinus tissues.   Biofilm is an important survival mechanism of bacteria allowing for attachment to surfaces.  The biofilm has been described to have an enhanced resistance to antibiotics and is associated with more severe disease and worse surgical outcomes.  Dr. Hamilos explains that less is known about viral or fungal infection in CRS; in fact it remains unclear if upper respiratory tract viruses contribute causally to CRS analogous to their possible role in asthma.  Other research has ruled out defects, such as defects in mucociliary clearance or toll like receptor function as primary defects in CRS.  A decreased level of the antimicrobial protein lactoferrin has been found in sinus secretions, however other antimicrobial protein levels have been found  to be normal. 

CRS research has focused on patients that have either “refractory” disease which can be defined as no improvement following  surgery  and medical management or “recalcitrant” disease which is defined as the recurrence of nasal polyps after polyp surgery.  Studies suggest that patients with recalcitrant nasal polyps have down regulated innate immunity associated with T helper type 2 (Th2) inflammation, potentially causing persistent infection.   While surgical treatment and use of culture-directed antibiotics remain the best treatment options, Dr. Hamilos is hopeful that further understanding of the underlying genetics of CRS and host-microbial interactions will allow for greater insight and more effective treatment options.

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