In vitro activity of difloxacin hydrochloride (A-56619), A-56620, and cefixime (CL 284,635; FK 027) against selected genital pathogens.

Management of sexually transmitted diseases is facilitated by having antimicrobial agents with activity against all of the major genital pathogens. Newer quinolones show promise of being active against Neisseria gonorrhoeae and Chlamydia trachomatis. Two quinolones, difloxacin (A-56619) and A-56620, and an oral cephalosporin, cefixime (CL 284,635; FK 027), were evaluated in vitro. All three were highly active against 400 isolates of N. gonorrhoeae, including penicillinase-producing N. gonorrhoeae, N. gonorrhoeae with chromosomally mediated resistance, and isolates with penicillin MICs of less than 1 microgram/ml. Susceptibilities to one antimicrobial agent were usually strongly correlated with susceptibilities to the other antimicrobial agents evaluated, but isolates with increasing resistance to beta-lactams were least likely to show increasing resistance to quinolones. Difloxacin and, to a lesser extent, A-56620 were active against all 10 strains of C. trachomatis, and both had moderate activity against over 200 strains of Gardnerella vaginalis. Based on in vitro activity, difloxacin and A-56620 merit in vivo assessment for management of both C. trachomatis and N. gonorrhoeae infections, and cefixime shows considerable promise for treatment of N. gonorrhoeae infections.