Relationship between bacterial flora in sputum and functional impairment in patients with acute exacerbations of COPD. Study Group of Bacterial Infection in COPD.

STUDY OBJECTIVES

To investigate the possible relationship between functional respiratory impairment measured by FEV1 and isolation of diverse pathogens in the sputum of patients with exacerbations of COPD.

DESIGN

Multicenter, cross-sectional, epidemiologic study.

SETTING

Pneumology units in six secondary or tertiary hospitals in Spain.

PATIENTS

Ninety-one patients with acute exacerbation of COPD were included.

INTERVENTIONS

A quantitative sputum culture was performed, and bacterial growth was considered significant only when the germ was isolated at concentrations > 10(6) cfu (> 10(5) for Streptococcus pneumoniae) in samples with < 10 epithelial cells and > 25 leukocytes per low magnification field (x 100).

RESULTS

Germs isolated were the following: Haemophilus influenzae (20 cases; 22%), Pseudomonas aeruginosa (14 cases; 15%), S. pneumoniae (9 cases; 10%), Moraxella catarrhalis (8 cases; 9%), other gram-negative bacteria (7 cases; 7%), and non-potentially pathogenic microorganisms (non-PPMs; 33 cases; 36%). P. aeruginosa and H. influenzae were isolated more frequently among the patients with FEV1 < 50% than among those with FEV1 > 50% (p < 0.05). All patients with P. aeruginosa in sputum had FEV1 < 1,700 mL. FEV1 < 50% was associated with a very high risk of P. aeruginosa or H. influenzae isolation: the odds ratios (ORs) are 6.62 (95% confidence interval [CI], 1.2 to 123.6) and 6.85 (95% CI, 1.6 to 52.6), respectively. Furthermore, active tobacco smoking was associated with a high risk of H. influenzae isolation (OR, 8.1; 95% CI, 1.9 to 43.0).

CONCLUSIONS

Patients with the greatest degree of functional impairment, as measured by their FEV1, presented a higher probability of having an isolation of P. aeruginosa or H. influenzae in significant concentrations in sputum during an exacerbation. The diagnostic yield of sputum in patients with an FEV1 > 50% was low, with a predominance of non-PPMs. Low FEV1 and active tobacco smoking are data that should be considered when establishing an empiric antibiotic treatment for exacerbated COPD.