Relationship between bacterial colonisation and the frequency, character, and severity of COPD exacerbations.
BACKGROUND
Patients with chronic obstructive pulmonary disease (COPD) are prone to frequent exacerbations which are a significant cause of morbidity and mortality. Stable COPD patients often have lower airway bacterial colonisation which may be an important stimulus to airway inflammation and thereby modulate exacerbation frequency.


METHODS
Twenty nine patients with COPD (21 men, 16 current smokers) of mean (SD) age 65.9 (7.84) years, forced expiratory volume in 1 second (FEV(1)) 1.06 (0.41) l, FEV(1) % predicted 38.7 (15.2)%, FEV(1)/FVC 43.7 (14.1)%, inhaled steroid dosage 1.20 (0.66) mg/day completed daily diary cards for symptoms and peak flow over 18 months. Exacerbation frequency rates were determined from diary card data. Induced sputum was obtained from patients in the stable state, quantitative bacterial culture was performed, and cytokine levels were measured.


RESULTS
Fifteen of the 29 patients (51.7%) were colonised by a possible pathogen: Haemophilus influenzae (53.3%), Streptococcus pneumoniae (33.3%), Haemophilus parainfluenzae (20%), Branhamella catarrhalis (20%), Pseudomonas aeruginosa (20%). The presence of lower airway bacterial colonisation in the stable state was related to exacerbation frequency (p=0.023). Patients colonised by H influenzae in the stable state reported more symptoms and increased sputum purulence at exacerbation than those not colonised. The median (IQR) symptom count at exacerbation in those colonised by H influenzae was 2.00 (2.00-2.65) compared with 2.00 (1.00-2.00) in those not colonised (p=0.03). The occurrence of increased sputum purulence at exacerbation per patient was 0.92 (0.56-1.00) in those colonised with H influenzae and 0.33 (0.00-0.60) in those not colonised (p=0.02). Sputum interleukin (IL)-8 levels correlated with the total bacterial count (rho=0.459, p=0.02).


CONCLUSIONS
Lower airway bacterial colonisation in the stable state modulates the character and frequency of COPD exacerbations.
Academic Respiratory Medicine, St Bartholomew's and Royal London School of Medicine and Dentistry, London EC1A 7BE, UK.
I S
IS
Patel
T A R
TA
Seemungal
M
M
Wilks
S J
SJ
Lloyd-Owen
G C
GC
Donaldson
J A
JA
Wedzicha
D000368:Aged; D000369:Aged, 80 and over; D001419:Bacteria / Q000254:growth & development*; D005260:Female; D005541:Forced Expiratory Volume; D006193:Haemophilus influenzae / Q000254:growth & development; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000382:microbiology* / Q000503:physiopathology; D012907:Smoking / Q000503:physiopathology; D013183:Sputum / Q000382:microbiology*; D014797:Vital Capacity