In vitro activity of A-56619 (difloxacin), A-56620, and other new quinolone antimicrobial agents against genital pathogens

Abstract

The in vitro activities of two new carboxyquinolones, A-56619 (difloxacin) and A-56620, were compared with those of ciprofloxacin, norfloxacin, and ofloxacin against genital tract pathogens. All the quinolones were highly active against Neisseria gonorrhoeae. A-56619 had the lowest MICs against Chlamydia trachomatis (MIC range, 0.125 to 0.25 ,ug/ml) and Haemophilus ducreyi (MIC for 90% of isolates tested, 0.1 ,ug/ml).The newer quinolone antimicrobial agents have been shown to have excellent activity in vitro against gonococci, including ,B-lactamase-producing strains (3,11,13,16,18), and moderate activity in vitro against Chlamydia trachomatis (2,10,14).We compared the activities of A-56619 (difloxacin), A-56620, ciprofloxacin, norfloxacin, ofloxacin, and antimicrobial agents now used for the treatment of genital infections against clinical isolates of Neisseria gonorrhoeae, Haemophilus ducreyi, Gardnerella vaginalis, Ureaplasma urealyticum, and C. trachomatis.Antimicrobial reference standards and sources were as follows: A-56619, A-56620, and erythromycin, Abbott Lab of M. hominis and 2-day-old broth cultures of U. urealyticum were inoculated into 100 ,ul of twice the required final concentration of each of the antibiotic dilutions in U-well microtiter plates. Controls containing medium only, medium plus antimicrobial agent, and medium plus M. hominis or U. urealyticum were included. The microtiter plates were sealed and incubated at 37°C until the indicator in the Mycoplasma-Ureaplasma control well changed color. The MIC was defined as the lowest concentration of antimicrobial agent which prevented color change.MIC testing of C. trachomatis was performed by a modification of a previously described method (15). Inocula of a 1-ml suspension of C. trachomatis in Eagle minimum essential medium supplemented with fetal bovine serum (10% vol/vol), glutamine (1% [vol/vol] of stock solution of 30 mg/ml), and vitamins (1% vol/vol), containing approximately 1.6 x 108 inclusion-forming units per ml, were added to flat-bottomed plastic tubes containing a cover slip monolayer of cycloheximide-treated McCoy cells. After centrifugation at 3,500 x g at 35°C for 60 min, the medium was replaced with 1 ml of supplemental Eagle medium containing the antimicrobial agents tested. The tubes were incubated at 35°C for 48 h. The cover slips were removed, fixed with methanol, stained with iodine, and examined by bright-field illumination for the presence of inclusions. The MIC was defined as the lowest concentration of antimicrobial agent which prevented the appearance of any inclusion bodies.The MICs of the antimicrobial agents tested against isolates of N. gonorrhoeae, H. ducreyi, U. urealyticum, G. vaginalis, and C. trachomatis are shown in Tables 1 and 2. The quinolones, cefotaxime, and ceftazidime were highly active against gonococci, including P-lactamase-producing isolates. A-56619 and A-56620 were the most active quinolones against H. ducreyi. A-56619 was the most active quinolone against both the lymphogranuloma venereum and o...

Gardnerella vaginalis: characteristics, clinical considerations, and controversies

“…G. vaginalis strains were inhibited by clindamycin concentrations of .0.24 (79,139,171,222) ,ug/ml (115) or between 1 and 4 ,ug/ml (128,231) for G. vaginalis. The ranges of MICs of other quinolones were 0.025 to 16 (22) and 2 to 8 (128) ,ug/ml for difloxacin, 2 to 8 ,ug/ml for pefloxacin (115), and 8 to 32 ,ug/ml for norfloxacin (115).…”

In vitro activities of ofloxacin and four other new quinoline-carboxylic acids against Chlamydia trachomatis

“…Moreover, in vitro studies demonstrated a high order of susceptibility of Neisseria gonorrhoeae to ofloxacin (11, 13). However, comparatively few studies have been done on the activity of this drug against Chlamydia trachomatis (2, 3,9,11,16). Therefore, we compared the in vitro activities of ofloxacin and four other quinoline-carboxylic acids with the activities of minocycline and doxycycline against 2 standard strains and 45 clinical isolates of C. trachomatis.…”

In vitro activities of T-3262, NY-198, fleroxacin (AM-833; RO 23-6240), and other new quinolone agents against clinically isolated Chlamydia trachomatis strains

“…This study also showed that T-3262 is very effective against C. trachomatis in vitro. Recently, the effectiveness of some other quinolone drugs was reported (4,11,18), but T-3262 is more effective.…”