INCIDENCE OF NEISSERIA-GONORRHOEAE ISOLATES NEGATIVE BY SYVA DIRECT FLUORESCENT-ANTIBODY TEST BUT POSITIVE BY GEN-PROBE ACCUPROBE TEST IN ASEXUALLY-TRANSMITTED DISEASE CLINIC POPULATION

To determine the accuracy of the Syva (Palo Alto, Calif.) direct fluor escent-antibody (DFA) test in comparison with the Gen-Probe (San Diego , Calif.) Accuprobe culture confirmation test, we tested 395 isolates of Neisseria gonorrhoeae from cultures obtained from patients attendin g a sexually transmitted disease clinic from 1 July 1991 through 30 Ju ne 1992. All isolates were tested for DFA reactivity with a polyclonal reagent (Difco Laboratories, Detroit, Mich.) and a monoclonal reagent (Syva, Inc., direct specimen test) and for specific molecular probe r eactivity by the Gen-Probe Accuprobe culture confirmation test for N. gonorrhoeae. The 395 isolates gave positive results for the Gen-Probe culture confirmation test and the Difco polyclonal direct specimen tes t. However, 18 (4.6%) of the isolates were negative for N. gonorrhoeae by the Syva DFA test. With the exception of six beta-lactamase-positi ve isolates, all isolates that were negative by Syva DFA were sensitiv e to penicillin, tetracycline, spectinomycin, and ceftriaxone by disk- diffusion susceptibility testing. Auxotyping and serotyping studies in dicated that strains negative by Syva DFA consisted of several variant s. The frequency of N. gonorrhoeae isolates showing negative results b y Syva DFA in this patient population ranged from 0 to 11.5%/month. La boratories using only the Syva DFA test for confirmation of N. gonorrh oeae may incur a significant risk of misidentification.