Intramucosal bacterial microcolonies exist in chronic rhinosinusitis without inducing a local immune response.
BACKGROUND
Although chronic rhinosinusitis (CRS) causes very significant morbidity, much about its pathogenesis remains uncertain. Recent studies have identified polymicrobial biofilms on the surface of sinus mucosa and Staphylococcus aureus within the sinus mucosa  of patients with CRS, both with and without nasal polyps. The pathogenic implications of intramucosal bacteria in CRS are unknown. This study was designed to determine the prevalence and species of bacterial colonies within the sinus mucosa of adult patients with and without CRS and to describe  the relationship of these bacterial colonies to the host immune response.


METHODS
Sinus mucosa from patients with and without CRS was examined using Gram and Giemsa staining, immunohistochemistry, bacterial culture, and fluorescence in situ hybridization techniques.


RESULTS
Bacterial microcolonies were observed within the mucosa in 14 of 18 patients with CRS. In 10 of these patients colonies were positively identified as S. aureus. Staphylococcal microcolonies were observed at a lower level (1 of 8 patients) in normal sinus mucosa.  There was no correlation between detection of S. aureus on the mucosal surface and microcolonization of the mucosa. Surprisingly, there was no evidence of an immune reaction to microcolonies. Indeed, fewer T lymphocytes (p = 0.03) and eosinophils (p = 0.03) were counted immediately  surrounding the microcolonies compared with uninfected areas of the same tissue.


CONCLUSIONS
Bacterial microcolonies are prevalent within paranasal sinus mucosa and are commonly S. aureus. These microcolonies do not provoke immune detection and may represent a phenotype  that actively evades host immunity. This may underpin the recalcitrance of CRS to antibiotic therapy. These findings challenge classic views of both infection and mucosal immunity in human chronic disease. The presence of intramucosal bacteria in samples of normal sinus mucosa also questions  the sensitivity of detecting nasal carriage of pathogens by swabbing the surface of the anterior nares.
Department of Otolaryngology-Head and Neck Surgery, Auckland City Hospital, Auckland, New Zealand.
Andrew J
AJ
Wood
John D
JD
Fraser
Simon
S
Swift
Emma A C
EA
Patterson-Emanuelson
Satya
S
Amirapu
Richard G
RG
Douglas
D000328:Adult; D000368:Aged; D002908:Chronic Disease; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008875:Middle Aged; D009297:Nasal Mucosa / Q000382:microbiology*; D012220:Rhinitis / Q000276:immunology / Q000382:microbiology*; D012852:Sinusitis / Q000276:immunology / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000302:isolation & purification*