DRIFT IN SUSCEPTIBILITY OF NEISSERIA-GONORRHOEAE TO CIPROFLOXACIN ANDEMERGENCE OF THERAPEUTIC FAILURE

Ciprofloxacin, 500 mg, was introduced as the first-line therapy for go norrhea at St, Mary's Hospital, London, in 1989, when a surveillance p rogram was initiated to detect the emergence of resistance. Isolates o f Neisseria gonorrhoeae from consecutive patients attending the Jeffer iss Wing, Genitourinary Medicine Clinic at St. Mary's Hospital, betwee n 1989 and 1997 have been tested for susceptibility to ciprofloxacin b y using an agar dilution breakpoint technique, Isolates considered pot entially resistant (MIC, >0.12 mu g/ml) were further characterized by determination of the MICs of ciprofloxacin, nalidixic acid, and penici llin, auxotyped and serotyped, and screened for mutations in the DNA g yrase gene, gyrA, and the topoisomerase IV gene, parC. A total of 4,87 5 isolates were tested. While the majority of isolates were highly sus ceptible (MIC, less than or equal to 0.008 mu g of ciprofloxacin/ml), there was a drift toward reduced susceptibility in N. gonorrhoeae isol ated between 1993 and 1996 (P < 0.001), In 1997 this drift was reduced but remained above pre-1993 levels. Isolates from 18 patients were cl assed as potentially resistant (MIC, >0.12 mu g/ml); all of these belo nged to serogroup B, and NR/IB-1 was the most common auxotype/serovar class. The infections in 14 of the 18 patients were known to be acquir ed abroad, and 5 were known to result in therapeutic failure. The surv eillance program has established that ciprofloxacin is still a highly effective antibiotic against N. gonorrhoeae in this population. Howeve r, it has identified a drift in susceptibility which may have resulted from increased usage of ciprofloxacin, High-level resistance has now emerged, although treatment failure is still uncommon.