Study entry microbiology in patients with acute bacterial exacerbation of chronic bronchitis in a clinical trial stratifying by disease severity.

OBJECTIVE

To examine study entry microbiology in patients stratified by disease severity in a clinical trial in acute bacterial exacerbation of chronic bronchitis (ABECB).

METHODS

Patients were assigned to differing antibiotic therapies based on stratification by disease severity using parameters including forced expiratory volume in 1 second (FEV(1)) as a percentage of predicted value, number of exacerbations during the previous 12 months, and defined co-morbidities. All patients were required to have sputum Gram stain and culture at study entry.

RESULTS

There was no statistically significant difference in overall microbiology between patients with less severe and more severe clinical presentations. Typical ABECB pathogens (Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis) were found in 46.2% (147/318) of patients with less severe presentations and 41.9% (143/341) of patients with more severe presentations. Gram-negative organisms and Staphylococcus aureus were also found in both groups. Pneumococcal susceptibilities to the three antibiotics utilized in the trial revealed marked resistance to azithromycin. Limitations of this analysis include that the clinical trial was designed to examine clinical outcomes rather than microbiology, and that we do not correlate study entry microbiology with clinical outcomes.

CONCLUSIONS

Stratification of patients by disease severity did not reveal a statistically significant difference in overall microbiological profile. Gram-negative organisms and S. aureus were recovered even from patients with less severe clinical presentations. Pneumococcal resistance varied with the agent tested. These findings may have implications for the selection of appropriate antibiotic therapy.