Although most
respiratory tract infections (RTI) are caused by viruses, various bacteria, particularly Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, are common causes of community-acquired
pneumonia, acute exacerbations of
chronic bronchitis,
otitis media and
sinusitis. Empirical
antibiotic therapy of patients with RTI must take account of the increasing prevalence of resistance among the predominant pathogens. Europe-wide susceptibility surveillance studies have revealed that resistance to
penicillin and
macrolides is highly prevalent among isolates of S. pneumoniae from France and Spain. Uniquely, in Italy,
macrolide resistance is highly prevalent while the prevalence of penicillin resistance is low. Resistance to other
antibiotic classes, including
chloramphenicol,
doxycycline and, in particular,
co-trimoxazole, is associated with penicillin resistance in pneumococci, but resistance to the
fluoroquinolones is rare.
beta-Lactamase production is the principal mechanism of resistance in isolates of H. influenzae and M. catarrhalis, with
fluoroquinolone resistance being detected rarely in these pathogens. In 1998 a surveillance study involving 15 European countries determined the susceptibilities of many respiratory pathogens to a range of antimicrobials, including
grepafloxacin. The MIC(90) of
grepafloxacin for 1251 isolates of S. pneumoniae was 0.25 mg/L, the MICs for only five strains being >2 mg/L, and 99.4% of all of the isolates tested were inhibited by concentrations </=0.5 mg/L. The MIC(90)s of
grepafloxacin for 587 isolates of H. influenzae and 323 of Haemophilus parainfluenzae were 0.015 and 0.06 mg/L, respectively, while that for 509 isolates of M. catarrhalis was 0.03 mg/L. The MIC(90)s for 1164 isolates of
methicillin-susceptible Staphylococcus aureus and 435 isolates of Klebsiella pneumoniae were 0.12 and 0.25 mg/L, respectively. Other studies have shown
grepafloxacin to be highly active against clinical isolates of Legionella pneumophila (MIC(90) 0.015 mg/L), Mycoplasma pneumoniae (MIC(90) 0.5 mg/L) and Chlamydia pneumoniae (MICs 0.06-0.12 mg/L). Current susceptibility data indicate that
fluoroquinolone resistance rates among bacterial respiratory tract pathogens are low in European countries. The enhanced potency and activity of
grepafloxacin against isolates of S. pneumoniae, including those exhibiting resistance to unrelated classes of
antibiotics, together with its activity against other respiratory tract pathogens, suggest that this
drug has considerable potential as empirical
therapy of patients with a wide range of RTI.