Lower respiratory tract infections (LRTI) are the leading infectious cause of death in most developed countries; community acquired pneumonia (CAP) and acute exacerbations of chronic bronchitis (AECB) are responsible for the bulk of the adult morbidity. Until recently quinolone antibiotics were not recommended for the routine treatment of these infections.1-3 Neither ciprofloxacin nor ofloxacin have adequate activity againstStreptococcus pneumoniae in vitro, and life threatening invasive pneumococcal disease has been reported in patients treated for respiratory tract infections with these drugs.4-6 The development of new fluoroquinolone agents with increased activity against Gram positive organisms, combined with concerns about increasing microbial resistance to β-lactam agents, has prompted a re-evaluation of the use of quinolones in LRTI. Sparfloxacin and levofloxacin are now approved for the treatment of community acquired LRTIs in the UK (grepafloxin, which was also approved for this indication, has recently been withdrawn from the market). It is important to define the role of these drugs in the treatment of CAP and AECB.

The most common cause of CAP worldwide is S pneumoniae which accounts for 60–75% of pathogens isolated.7-9 Other less common causes includeMycoplasma pneumoniae andLegionella pneumophila. Any agent used for the empirical treatment of CAP must cover S pneumoniae, and preferably these other organisms as well, especially in severe disease. In AECB the role of bacterial pathogens is less clearly defined; Haemophilus influenzae, S pneumoniae, andMoraxella catarrhalis are most frequently associated. Several of the newer quinolones have MIC₉₀values for S pneumoniae that are significantly lower than those reported for ofloxacin and ciprofloxacin, which …