Haemophilus influenzae in respiratory tract infections in community-based clinical practice: therapy with gatifloxacin

In this community-based safety surveillance study, the advanced-generation fluoroquinolone gatifloxacin was administered empirically to 15,625 adults with community-acquired respiratory tract infections (RTIs), including 1562 clinically evaluable patients with community-acquired pneumonia (CAP) and 2391 with acute exacerbations of chronic bronchitis (AECB). Haemophilus influenzae was the most common pathogen isolated in AECB (40.1%) and the second most common in CAP (36.8%). In vitro susceptibility to gatifloxacin and other fluoroquinolones, amoxicillin/clavulanate, ceftriaxone, cefuroxime axetil, tetracycline, and azithromycin ranged from 95.8% to 100%. In comparison, a significant percentage of the isolates were not susceptible to clarithromycin (∼41%), ampicillin (22% to 28%), and trimethoprim/sulfamethoxazole (14% to 18%). The susceptibility pattern was generally independent of exposure to another antimicrobial in the previous 30 days. CAP and AECB patients infected with H. influenzae had signs and symptoms similar to those infected with Streptococcus pneumoniae. Among clinically evaluable patients with H. influenzae, gatifloxacin cured 159 of 166 (95.8%) with AECB and 112 of 118 (94.9%) with CAP. The cure rate was independent of the β-lactamase status or serotype of the H. influenzae strain. H. influenzae is not a more benign pathogen in community-acquired RTIs but causes signs and symptoms that are indistinguishable from those caused by other pathogens, notably S. pneumoniae.