Comparative bactericidal activity of cefixime, carumonam, enoxacin and roxithromycin with those of other antibiotics against resistant Haemophilus influenzae including beta-lactam tolerant strains.
One hundred isolates of Haemophilus influenzae including 50 beta-lactamase producing, five ampicillin-resistant non-beta-lactamase producing and five beta-lactam tolerant strains were tested for susceptibility (MICs and MBCs) to ampicillin, aztreonam, carumonam, cefixime, cefaclor, cefamandole, cefotaxime, imipenem, enoxacin, ciprofloxacin, roxithromycin, erythromycin, chloramphenicol, and co-trimoxazole, by a microdilution broth method. Cefotaxime, enoxacin and ciprofloxacin with MIC90 and MBC90 of less than 0.03 mg/l) were the most active antimicrobial agents tested. Cefixime, carumonam, aztreonam, and co-trimoxazole (MIC90 and MBC90 less than 0.25 mg/l) showed good activity against most strains. Roxithromycin and erythromycin had limited antibacterial activity (MIC90, 8 and 4 mg/l respectively). There were no chloramphenicol-resistant strains. Five beta-lactamase-negative strains were resistant to ampicillin, cefaclor and cefamandole but susceptible to other beta-lactams tested. Different patterns of tolerance were observed: four of five tolerant strains were tolerant to ampicillin and cefamandole, three to cefixime, cefaclor and cefotaxime, one to aztreonam. One tolerant strain was a beta-lactamase producer. Two other strains were tolerant only to co-trimoxazole.
D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001398:Aztreonam / Q000031:analogs & derivatives*; D020682:Cefixime; D002439:Cefotaxime / Q000031:analogs & derivatives / Q000494:pharmacology; D015365:Enoxacin; D006193:Haemophilus influenzae / Q000187:drug effects*; D007933:Leucomycins / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D009287:Naphthyridines / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D007933:Leucomycins; D009287:Naphthyridines; D015365:Enoxacin; C044145:carumonam; D000667:Ampicillin; D020682:Cefixime; D001398:Aztreonam; D002439:Cefotaxime