TRENDS IN SUSCEPTIBILITY OF NEISSERIA-GONORRHOEAE TO CEFTRIAXONE FROM1985 THROUGH 1991

The antimicrobial susceptibilities of 16,441 gonococcal isolates from Seattle-King County were determined for ceftriaxone, cefoxitin, penici llin G, and tetracycline. From 1985 to 1989, ceftriaxone, in combinati on with doxycycline, was increasingly used for treatment of gonorrhea, and by 1989, it was used as therapy for >80% of cases in Seattle-King County. MICs of ceftriaxone correlated significantly (P < 0.001) with those of the other beta-lactam antibiotics included in this study. Ge ometric mean MICs of penicillin G for isolates that did not produce be ta-lactamase increased from 1985 to 1991. The geometric mean MICs of c efoxitin, ceftriaxone, and tetracycline began to decline in 1987 but i ncreased in 1990 and 1991. The percentage of strains with decreased su sceptibility to ceftriaxone (MIC, 0.06 to 0.25 mu g/ml) rose from 0.3% in 1985 to 5.3% in 1987 but subsequently declined steadily to 2.6% in 1991, despite increased use of ceftriaxone as routine therapy for gon orrhea. Changes in patterns of antimicrobial susceptibility may be rel ated not only to antimicrobial selection pressures but also to less we ll understood population shifts among Neisseria gonorrhoeae strains wi thin a community.