In vitro activity of trovafloxacin (CP-99,219), sparfloxacin, ciprofloxacin, and fleroxacin against respiratory pathogens

Favourable clinical outcomes are usually observed when respiratory tract infections are treated with fluoroquinolones (1). However, despite their broad in vitro antibacterial spectrum, which includes the common respiratory pathogens Chlamydia pneumoniae, Mycoplasma pneumoniae (2), Haemophilus influenzae, and Moraxella catarrhalis, most fluoroquinolones lack activity against gram-positive microorganisms and anaerobes (3). This is of particular concern in aspiration pneumonia or in community-acquired respiratory tract infections in which Streptococcus pneumoniae or Staphylococcus aureus may be involved. Peak serum concentrations achievable after oral administration of trovafloxacin, a new fluoronaphthyridone (4), are approximately 2 to 3 mg/l, exceeding the MICs for most respiratory pathogens. Most quinolones are bactericidal at concentrations equal to the MIC or within a two-fold dilution. Moreover, this high killing rate is rapidly obtained, and the in vitro activity has been already correlated with in vivo activity in some studies (5, 6).