title: Bacteria in sputum of stable severe asthma and increased airway wall thickness.
abstract: BACKGROUND
  Patients with chronic asthma have thicker intrapulmonary airways measured on high resolution computed tomography (HRCT). We determined whether the presence of lower airway bacteria was associated with increased airway wall thickness.
  
  
  METHODS
  In 56 patients with stable severe asthma, sputum specimens obtained either spontaneously or after induction with hypertonic saline were cultured for bacteria and thoracic HRCT scans obtained. Wall thickness (WT) and area (WA) expressed as a ratio of airway diameter (D) and total area, respectively, were measured at five levels.
  
  
  RESULTS
  Positive bacterial cultures were obtained in 29 patients, with H. influenzae, P. aeruginosa and S. aureus being the commonest strains. Logistic regression analysis showed that this was associated with the duration of asthma and the exacerbations during the past year. In airways > 2 mm, there was no significant difference in WA (67.5 ± 5.4 vs 66.4 ± 5.4) and WT/D (21.6 ± 2.7 vs 21.3 ± 2.4) between the culture negative versus positive groups. Similarly, in airways (≤ 2 mm), there were no significant differences in these parameters. The ratio of √wall area to Pi was negatively correlated with FEV1% predicted (p < 0.05).
  
  
  CONCLUSIONS
  Bacterial colonization of the lower airways is common in patients with chronic severe asthma and is linked to the duration of asthma and having had exacerbations in the past year, but not with an increase in airway wall thickness.
authors.affiliation: Airways Disease Section, National Heart & Lung Institute, Imperial College, London, UK.
authors.forename: Qingling
authors.initials: Q
authors.lastname: Zhang
authors.forename: Rowland
authors.initials: R
authors.lastname: Illing
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Hui
authors.forename: Kate
authors.initials: K
authors.lastname: Downey
authors.forename: Denis
authors.initials: D
authors.lastname: Carr
authors.forename: Martin
authors.initials: M
authors.lastname: Stearn
authors.forename: Khalid
authors.initials: K
authors.lastname: Alshafi
authors.forename: Andrew
authors.initials: A
authors.lastname: Menzies-Gow
authors.forename: Nanshan
authors.initials: N
authors.lastname: Zhong
authors.forename: Kian
authors.initials: K
authors.lastname: Fan Chung
mesh_terms: D000328:Adult; D000368:Aged; D056151:Airway Remodeling; D001249:Asthma / Q000000981:diagnostic imaging / Q000382:microbiology*; D005260:Female; D005541:Forced Expiratory Volume; D006193:Haemophilus influenzae / Q000302:isolation & purification*; D006801:Humans; D016015:Logistic Models; D008168:Lung / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011550:Pseudomonas aeruginosa / Q000302:isolation & purification*; D012720:Severity of Illness Index; D013183:Sputum / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000302:isolation & purification*; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods