Anti-pneumococcal activity of gatifloxacin compared with other quinolone and non-quinolone agents.
An agar dilution MIC method was used to test the activity of gatifloxacin, a new broad-spectrum fluoroquinolone, compared with ciprofloxacin, levofloxacin, sparfloxacin, trovafloxacin, amoxycillin, cefuroxime, ceftriaxone and clarithromycin against 71 penicillin-susceptible, 81 penicillin-intermediate and 55 penicillin-resistant pneumococci. Quinolone activity was unaffected by penicillin susceptibility, with MIC50/MIC90s (mg/L) of 0.25/0.5 for gatifloxacin; 1/2 for ciprofloxacin; 1/2 for levofloxacin; 0.25/0.5 for sparfloxacin; 0.125/0.25 for trovafloxacin. beta-Lactam and clarithromycin MICs rose with those of penicillin G; MIC50/MIC90 values (mg/L) for penicillin-susceptible, -intermediate and -resistant strains were: 0.03/0.06, 0.25/1, 2/4 for penicillin G; 0.03/0.03, 0.125/1, 2/4 for amoxycillin; 0.03/0.125, 0.5/4, 8/16 for cefuroxime; 0.03/0.03, 0.25/0.5, 2/4 for ceftriaxone; 0.03/0.06, 0.03/>64, 1/>64 for clarithromycin. Time-kill testing of four penicillin-susceptible, four -intermediate and four -resistant strains showed that levofloxacin at the MIC, gatifloxacin and sparfloxacin at 2 x MIC, and trovafloxacin and ciprofloxacin at 4 x MIC, were bactericidal (99.9% killing) for all strains after 12 h and 24 h. By contrast, amoxycillin, cefuroxime and ceftriaxone showed bactericidal activity after 24 h against all strains at 4, 8 and 4 x MIC, respectively. Against ten organisms with clarithromycin MICs of 0.03-4.0 mg/L, clarithromycin was bactericidal against seven strains at 8 x MIC after 24 h. Quinolones showed more rapid killing at lower concentrations and earlier time periods than did beta-lactams and clarithromycin.
Hoellman
D B
DB
Department of Pathology, Hershey Medical Center, PA 17033, USA.
Lin
G
G
Jacobs
M R
MR
Appelbaum
P C
PC
D000658:Amoxicillin / Q000494:pharmacology; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002443:Ceftriaxone / Q000494:pharmacology; D002444:Cefuroxime / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology; D002939:Ciprofloxacin / Q000494:pharmacology; D017291:Clarithromycin / Q000494:pharmacology; D024841:Fluoroquinolones; D000077734:Gatifloxacin; D064704:Levofloxacin; D008826:Microbial Sensitivity Tests; D009287:Naphthyridines / Q000494:pharmacology; D015242:Ofloxacin / Q000494:pharmacology; D010403:Penicillin Resistance; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000502:physiology
D000890:Anti-Infective Agents; D002511:Cephalosporins; D024841:Fluoroquinolones; D009287:Naphthyridines; D002939:Ciprofloxacin; D064704:Levofloxacin; D002443:Ceftriaxone; D000658:Amoxicillin; C080163:trovafloxacin; D015242:Ofloxacin; D017291:Clarithromycin; D000077734:Gatifloxacin; D002444:Cefuroxime; C061363:sparfloxacin