Respiratory pathogens: assessing resistance patterns in Europe and the potential role of grepafloxacin as treatment of patients with infections caused by these organisms

Although most respiratory tract infections (RTI) are caused by viruses, var ious bacteria, particularly Streptococcus pneumoniae, Haemophilus influenza e and Moraxella catarrhalis, are common causes of community-acquired pneumo nia, 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. Europ e-wide susceptibility surveillance studies have revealed that resistance to penicillin and macrolides is highly prevalent among isolates of S. pneumon iae from France and Spain. Uniquely, in Italy, macrolide resistance is high ly prevalent while the prevalence of penicillin resistance is low. Resistan ce 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-Lactamas e production is the principal mechanism of resistance in isolates of H. inf luenzae and M. catarrhalis, with fluoroquinolone resistance being detected rarely in these pathogens. In 1998 a surveillance study involving 15 Europe an countries determined the susceptibilities of many respiratory pathogens to a range of antimicrobials, including grepafloxacin. The MIC90 of grepafl oxacin 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 in hibited by concentrations less than or equal to 0.5 mg/L. The MIC(90)s of g repafloxacin for 587 isolates of H. influenzae and 323 of Haemophilus parai nfluenzae were 0.015 and 0.06 mg/L, respectively, while that for 509 isolat es of M, catarrhalis was 0.03 mg/L. The MIC90S for 1164 isolates of methici llin-susceptible Staphylococcus aureus and 435 isolates of Klebsiella pneum oniae were 0.12 and 0.25 mg/L, respectively. Other studies have shown grepa floxacin to be highly active against clinical isolates of Legionella pneumo phila (MIC90 0.015 mg/L), Mycoplasma pneumoniae (MIC90 0.5 mg/L) and Chlamy dia pneumoniae (MICs 0.06-0.12 mg/L). Current susceptibility data indicate that fluoroquinolone resistance rates among bacterial respiratory tract pat hogens 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 cons iderable potential as empirical therapy of patients with a wide range of RT I.