THE COMPARATIVE ACTIVITY OF 12 4-QUINOLONE ANTIMICROBIALS AGAINST HEMOPHILUS-INFLUENZAE AND STREPTOCOCCUS-PNEUMONIAE

  • 1 January 1985
    • journal article
    • research article
    • Vol. 11  (4) , 259-262
Abstract
The minimal inhibitory concentrations (MIC) of twelve 4-quinolone antimicrobials [nalidixic acid, pipemidic acid, cinoxacin, oxolinic acid, flumequine, pefloxacin, rosoxacin, norfloxacin, enoxacin, ofloxacin, ciprofloxacin and WIN 49375 (amifloxacin)] were determined for 100 isolates of H. influenzae (including 30 .beta.-lactamase producing strains) and 100 isolates of s. pneumoniae. MIC were determined using an agar dilution technique in Mueller-Hinton agar supplemented with 10% lysed horse blood. The inoculum used was .apprx. 104 colony-forming units, contained in 10.mu.l of Mueller-Hinton broth, which was applied to the agar plates using a multipoint inoculator. Following inoculation, plates were incubated at 37% C for 18 h in an atmosphere enriched to 10% CO2. The MIC of each antimicrobial for each isolate examined was determined as the lowest concentration of the antimicrobial which completely inhibited growth of the inoculum. The minimum concentrations required to inhibit the growth of 50% (MIC50) and 90% (MIC90) of the organisms examined were also determined. The more recently synthesized 4-quinolones showed considerably greater activity than nalidixic acid and pipemidic acid against clinical isolates of H. influenzae and S. pneumoniae. There was no apparent difference between the MIC observed for .beta.-lactamase producing and non-.beta.-lactamase producing strains of H. influenzae. Ciprofloxacin was the most active 4-quinolone examined (MIC90 for H. influenzae 0.008.mu.g/ml; S. pneumoniae 2 .mu.g/ml). Clinical studies on a possible role of some of the more recently synthesized 4-quinolones in the management of patients with respiratory infection are indicated.