title: Gram-negative bacterial carriage in chronic rhinosinusitis with nasal polyposis is not associated with more severe inflammation.
abstract: BACKGROUND
  We have previously demonstrated that persistent symptoms following functional endoscopic sinus surgery for chronic rhinosinusitis (CRS) is associated with Gram-negative bacterial carriage. Mechanisms for this remain unknown. We wished to determine whether Gram-negative carriage in patients with CRS with nasal polyposis is associated with a more severe inflammatory phenomenon.
  
  
  METHODS
  Three hundred and thirty-seven patients with CRS with nasal polyposis (CRSwNP) previously phenotyped for genetic association studies with questionnaire, serum biomarkers, and endoscopically-obtained swab cultures were studied. These were separated according to the presence (wGN) or absence (sGN) of Gram-negative bacterial carriage; demographic parameters and available serum biomarkers (complete blood count [CBC], total immunoglobulin E [IgE]) were then compared. Subgroup analysis for Pseudomonas aeruginosa (GNwPa) and non-Pseudomonas Gram-negative bacteria (GNsPs) was performed in order to explore potentially differential roles of these bacteria.
  
  
  RESULTS
  Gram-negative bacterial carriage was not associated with a difference in demographic parameters or serum biomarkers. However, P. aeruginosa carriage was associated with a higher self-reported incidence of asthma (GNwPa 79%, sGN 57%; p = 0.048). Interestingly, serum IgE was increased in the non-Pseudomonas Gram-negative population (GNsPs: 338 IU/mL, sGN: 195 IU/mL; p = 0.026).
  
  
  CONCLUSIONS
  CRSwNP patients colonized with Gram-negative bacteria have a similar pattern of inflammation as assessed by serum biomarkers to those colonized with Gram-positive ones. Gram-negative bacteria may contribute to development of a T helper 2 (Th2) phenotype via other mechanisms, possibly via Toll-like receptor 4 (TLR4)-mediated interleukin 33 (IL-33) production. Differences in phenotype associated with Pseudomonas species carriage suggest a different behavior than other Gram-negative bacteria, supporting their importance as disease modifiers in CRSwNP.
authors: Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Montreal, QC, Canada.
authors: Paul
authors: P
authors: Tabet
authors: Leandra Mfuna
authors: LM
authors: Endam
authors: Pierre
authors: P
authors: Boisvert
authors: Louis-Philippe
authors: LP
authors: Boulet
authors: Martin
authors: M
authors: Desrosiers
mesh_terms: D001249:Asthma / Q000453:epidemiology; D015415:Biomarkers / Q000097:blood; D002908:Chronic Disease; D006090:Gram-Negative Bacteria / Q000302:isolation & purification*; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology*; D006801:Humans; D007073:Immunoglobulin E / Q000097:blood; D015994:Incidence; D018836:Inflammation Mediators / Q000097:blood*; D008875:Middle Aged; D009298:Nasal Polyps / Q000382:microbiology*; D012220:Rhinitis / Q000382:microbiology*; D012852:Sinusitis / Q000382:microbiology*; D018417:Th1 Cells / Q000276:immunology
chemical_list: D015415:Biomarkers; D018836:Inflammation Mediators; D007073:Immunoglobulin E
keywords: Gram-negative bacteria; Pseudomonas aeruginosa; biomarkers; chronic rhinosinusitis; inflammation