Comparative in-vitro activity of levofloxacin against isolates of bacteria from adult patients with community-acquired lower respiratory tract infections.

This study was conducted to evaluate the activity of levofloxacin in comparison with a range of antibacterial agents against recent isolates obtained consecutively from patients with community-acquired pneumonia (CAP) or acute exacerbation of chronic bronchitis (AECB) during the period 1995 to 1996. Susceptibility testing was carried out by either microdilution or the Etest, and interpreted according to NCCLS breakpoints. The activity of levofloxacin was compared with that of amoxycillin, amoxycillin-clavulanate, cefuroxime, cefixime, erythromycin, roxithromycin, clarithromycin, azithromycin, ofloxacin and ciprofloxacin. Clinically significant numbers of bacteria were recovered from 31 CAP and 94 AECB specimens. The predominant bacterial species in the CAP specimens were Streptococcus pneumoniae (21 isolates) and Haemophilus influenzae (four isolates). The AECB isolates mainly consisted of S. pneumoniae (38%), Moraxella catarrhalis (26%), H. influenzae (19%) and Pseudomonas aeruginosa (10%). The overall percentage susceptible of the isolates for each antibiotic was: amoxycillin, 64%; amoxycillin-clavulanate, 89%; cefuroxime, 87%; cefixime, 78%; erythromycin, 85%; roxithromycin, 87%; clarithromycin, 87%; azithromycin, 85%; ofloxacin, 95%; ciprofloxacin, 95%; and levofloxacin, 97%. The activities of levofloxacin and the other agents were also compared against 40 S. pneumoniae isolates, of which 20 were penicillin-non-susceptible, recovered from CAP and AECB specimens during the period 1994 to 1996. These strains were all susceptible to levofloxacin, but only 50% were susceptible to ciprofloxacin and 80% to ofloxacin. Twenty M. catarrhalis, 20 H. influenzae and 20 methicillin-susceptible S. aureus isolates were also all susceptible to levofloxacin. Furthermore, 20 community-acquired P. aeruginosa isolates showed similar percentage susceptible rates to levofloxacin and ciprofloxacin. These in-vitro results suggest that levofloxacin may be useful in the treatment of community-acquired lower respiratory tract infections.