Etiology, susceptibility, and treatment of acute bacterial exacerbations of complicated chronic bronchitis in the primary care setting: ciprofloxacin 750 mg b.i.d. versus clarithromycin 500 mg b.i.d. Bronchitis Study Group.

Although controversial, antimicrobial therapy for the treatment of acute exacerbations of chronic bronchitis (AECB) appears beneficial in patients with a history of repeated infections, those who have comorbid illnesses, and those with marked airway obstruction. In a community-based, open, randomized trial, the efficacy and safety of ciprofloxacin (CIP) 750 mg and clarithromycin (CLA) 500 mg, each given twice daily for 10 days, were compared in 2180 patients with AECB (1083 CIP, 1097 CLA). Patients were >40 years of age and had complicated/severe AECB episodes defined as at least three episodes within the past year, at least three comorbid conditions, previous failed antibiotic treatment for AECB within the previous 2 to 4 weeks, or community susceptibility data indicating a high number of resistant pathogens. Significant bacterial isolates (>10(5) colony-forming units per milliliter) from homogenized sputa were identified. Susceptibility to a range of antimicrobials was determined by the microbroth dilution technique. The majority of patients were white (83%) and were current or previous smokers (81%). Mean patient age was 62 years. A history of at least three AECB episodes in the previous year was reported by 54% of CIP-treated patients and 53% of CLA-treated patients. Of 777 primary isolates positively identified and cultured from 673 patients, the bacterial pathogens isolated and their incidence included Haemophilus species, 28%; Moraxella catarrhalis, 18%; Enterobacteriaceae, 18%; Staphylococcus aureus, 17%; Streptococcus pneumoniae, 7%; and Pseudomonas aeruginosa, 4%. Beta-lactamase production was found in 38% of Haemophilus influenzae, 10% of Haemophilus parainfluenzae, and 85% of M catarrhalis isolates. Thirty-four percent of S pneumoniae isolates were resistant to penicillin (minimum inhibitory concentration > or =0.12 mg/L). Among the 673 patients who were valid for clinical assessment and had a pretherapy pathogen isolated, clinical success and overall bacteriologic eradication rates at the end of therapy were 93% and 98% for CIP versus 90% and 96% for CLA. The differences between CIP and CLA did not reach statistical significance. Superinfections were reported significantly more frequently in CLA-treated (3%) versus CIP-treated patients (1%). Eradication rates for specific organisms for CIP and CLA, respectively, were Haemophilus species, 99% and 93%; M catarrhalis, 99% and 100%; S pneumoniae, 91% and 92%; and Enterobacteriaceae, 100% and 95%. Drug-related adverse events occurred in 12% of CIP-treated patients and 10% of CLA-treated patients. CIP 750 mg b.i.d. had a higher (but not statistically significant) clinical and bacteriologic cure rate than CLA 500 mg b.i.d. in the treatment of patients with bacteriologically proven complicated/severe AECB. The causative bacterial pathogens of AECB appear to be evolving, with a predominance of gram-negative and other resistant organisms observed. Thus antibiotic therapy for at-risk patients with AECB should include agents that have activity against gram-negative pathogens.