Activities of three investigational fluoroquinolones (BAY y 3118, DU-6859a, and clinafloxacin) against Neisseria gonorrhoeae isolates with diminished susceptibilities to ciprofloxacin and ofloxacin.

Between 1 January 1992 and 31 December 1993, our laboratory, as part of the Gonococcal Isolate Surveillance Project, found that 39 of 673 isolates of Neisseria gonorrhoeae from one local sexually transmitted diseases clinic demonstrated decreased susceptibilities to both ciprofloxacin and ofloxacin. The MICs of BAY y 3118, DU-6859a, and clinafloxacin at which 90% of the gonococci with decreased susceptibility to ciprofloxacin and ofloxacin were inhibited were all 0.016 microgram/ml, which was eightfold higher than those for ciprofloxacin-susceptible gonococci. Our report substantiates prior observations that diminished susceptibility to one quinolone is often associated with diminished susceptibility to other quinolones.