title: Microbiologic determinants of exacerbation in chronic obstructive pulmonary disease.
abstract: BACKGROUND
  The culture of bronchial secretions from the lower airway has been reported to be positive for potentially pathogenic microorganisms (PPMs) in patients with stable chronic obstructive pulmonary disease (COPD), but the determinants and effects of this bacterial load in the airway are not established.
  
  
  METHODS
  To determine the bronchial microbial pattern in COPD and its relationship with exacerbation, we pooled analysis of crude data from studies that used protected specimen brush sampling, with age, sex, smoking, lung function, and microbiologic features of the lower airway as independent variables and exacerbation as the outcome, using logistic regression modeling.
  
  
  RESULTS
  Of 337 study participants, 70 were healthy, 181 had stable COPD, and 86 had exacerbated COPD. Differences in the microbial characteristics in the participating laboratories were not statistically significant. A cutoff point of 10(2) colony-forming units (CFU) per milliliter or greater for the identification of abnormal positive culture results for PPMs was defined using the 95th percentile in the pooled analysis of healthy individuals. Bronchial colonization of 10(2) CFU/mL or greater by PPMs was found in 53 patients with stable COPD (29%) and in 46 patients with exacerbated COPD (54%) (P<.001, chi(2) test), with a predominance of Haemophilus influenzae and Pseudomonas aeruginosa. Higher microbial loads were associated with exacerbation and showed a statistically significant dose-response relationship after adjustment for covariates (odds ratio, 3.62; 95% confidence interval, 1.47-8.90), but P aeruginosa persisted as a statistically significant risk factor after adjustment for microbial load (odds ratio, 11.12; 95% confidence interval, 1.17-105.82).
  
  
  CONCLUSIONS
  One quarter of the patients with COPD are colonized by PPMs during their stable periods. Exacerbation is associated with the overgrowth of PPMs and with the appearance of P aeruginosa in the lower airway, which is associated with exacerbation symptoms independent of load.
authors.affiliation: Servei de Pneumologia, Hospital Germans Trias i Pujol, 08916 Badalona, Spain.
authors.forename: Antoni
authors.initials: A
authors.lastname: Rosell
authors.forename: Eduard
authors.initials: E
authors.lastname: Monsó
authors.forename: Néstor
authors.initials: N
authors.lastname: Soler
authors.forename: Ferràn
authors.initials: F
authors.lastname: Torres
authors.forename: Joaquim
authors.initials: J
authors.lastname: Angrill
authors.forename: Gerdt
authors.initials: G
authors.lastname: Riise
authors.forename: Rafael
authors.initials: R
authors.lastname: Zalacaín
authors.forename: Josep
authors.initials: J
authors.lastname: Morera
authors.forename: Antoni
authors.initials: A
authors.lastname: Torres
mesh_terms: D000368:Aged; D001419:Bacteria / Q000254:growth & development / Q000302:isolation & purification*; D001424:Bacterial Infections / Q000150:complications / Q000453:epidemiology / Q000382:microbiology* / Q000503:physiopathology; D001980:Bronchi / Q000382:microbiology; D001999:Bronchoscopy; D015169:Colony Count, Microbial; D018450:Disease Progression; D005260:Female; D005541:Forced Expiratory Volume; D006192:Haemophilus Infections / Q000150:complications / Q000453:epidemiology / Q000382:microbiology / Q000503:physiopathology; D006193:Haemophilus influenzae / Q000254:growth & development / Q000302:isolation & purification; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D015995:Prevalence; D011552:Pseudomonas Infections / Q000150:complications / Q000453:epidemiology / Q000382:microbiology / Q000503:physiopathology; D011550:Pseudomonas aeruginosa / Q000254:growth & development / Q000302:isolation & purification; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000382:microbiology* / Q000503:physiopathology; D012189:Retrospective Studies; D012307:Risk Factors; D013183:Sputum / Q000382:microbiology*