The susceptibilities of 45 strains of Neisseria gonorrhoeae, including 25 strains susceptible to ciprofloxacin (MICs, <0.06 g/ml) and 20 strains exhibiting decreased susceptibilities to ciprofloxacin (MICs, >0.125 g/ml), to ciprofloxacin, ofloxacin, enoxacin, lomefloxacin, norfloxacin, and nalidixic acid were determined by agar dilution and disk diffusion. On the basis of theoretical calculations of predicted susceptibilities at which infections may fail therapy (supported by observed failures of infections to respond to the therapeutic doses of enoxacin and ciprofloxacin), the Centers for Disease Control and Prevention has adopted the following agar dilution breakpoints for interpretation of resistance to these agents: MICs of >1.0 g of ciprofloxacin, enoxacin, and norfloxacin per ml and MICs of >2.0 g of ofloxacin and lomefloxacin per ml. The corresponding disk diffusion breakpoints for these agents were as follows: ciprofloxacin, <29 mm; ofloxacin, <24 mm; enoxacin, <31 mm; lomefloxacin, <26 mm; and norfloxacin,

From 1991 through 1997, few gonococcal strains exhibiting intermediate or clinically significant resistance to CDC-recommended doses of fluoroquinolones were identified from Hawaii. Isolates belonged to a large number of phenotypic and genotypic types, suggesting that most cases were imported, with only a few instances in which isolate pairs indicated that secondary transmission of infections had occurred in Hawaii. Beginning in 1998, the number of CipR isolates increased markedly, and more isolates belonged to fewer phenotypic and genotypic types, suggesting either more frequent importation of fewer strain types or the possibility that the endemic spread of a few strains is beginning to occur.

The susceptibilities of37 penicillinase-producing strains ofNeisseria gonorrhoeae (PPNG), isolated Isolates were characterized by auxotype, serovar, and plasmid content as described previously (9, 11, 16); requirements for proline, arginine, hypoxanthine, uracil, and methionine were determined. Antimicrobial susceptibilities to penicillin, tetracycline, erythromycin, spectinomycin, ceftriaxone, cefixime, ciprofloxacin, and ofloxacin were determined by the agar dilution method as described previously (7,12

Patients and gonococcal isolates (n = 783) from five sexually transmitted disease clinics in Ohio and western Pennsylvania were studied to investigate the spread of gonococci with decreased fluoroquinolone susceptibility. Among patients with gonorrhea, rates of infection with strains with decreased fluoroquinolone susceptibility (MIC of 0.125-0.25 microg ciprofloxacin/mL) were 20% for Cleveland, 9% for Akron, 7% for Columbus, 1% for Toledo, and 0.5% for Pittsburgh. Persons infected with strains with decreased susceptibility were more likely than those with susceptible strains to be male and older; no significant differences in sex behaviors, residence of sex partners, or recent antibiotic use were detected. Prevalence of decreased susceptibility was not correlated with reported levels of community fluoroquinolone use. The Pro/IB-3 auxotype/serovar class accounted for 80% (44/55) of isolates with decreased susceptibility. Pro/IB-3 isolates from three cities had indistinguishable pulsed-field gel electrophoresis patterns, suggesting intercity spread of a clone.

Twenty-five isolates of ,-lactamase-negative strains of Neisseria gonorrhoeae exhibiting decreased susceptibilities to ciprofloxacin (MIC, .0.125 ,g/ml) were isolated from men with uncomplicated gonococcal urethritis in Cleveland, Ohio, from January 1992 through June 1993. The strains belonged to three auxotype-serovar classes: Pro-IB-1 (2 isolates), Pro-IB-2 (21 isolates), and Pro-IB-3 (2 isolates). MICs for strains were (MICs, '0.25 ,ug/ml) and spectinomycin (MIC, ,ug/ml). MICs for strains were also in the susceptible category for ofloxacin (MIC, 0.25 ,ug/ml) ciprofloxacin (5, 14). However, from January 1992 through June 1993, 22 isolates of N. gonorrhoeae for which MICs of ciprofloxacin were .0.125 ,ug/ml were identified in men with symptomatic, uncomplicated gonorrhea in Cleveland, Ohio (5).A total of 25 isolates of ,B-lactamase-negative N. gonorrhoeae were submitted to CDC for further examination; these isolates included 3, 6, and 16 isolates for which MICs of ciprofloxacin were 0.06, 0.125, and 0.25 jig/ml, respectively. Isolates were stored frozen at -70°C in trypticase soy broth (Difco Laboratories, Detroit, Mich.) containing 15% glycerol. Isolates were characterized by auxotype and serovar as described previously (9, 15); requirements for proline (Pro), arginine, hypoxanthine, uracil, and methionine were determined.Antimicrobial susceptibilities to penicillin, tetracycline, erythromycin, spectinomycin, ceftriaxone, cefixime, ciprofloxacin, and ofloxacin were determined by the agar dilution method as described previously (10,13