Evaluation of GonoGen coagglutination test for serodiagnosis of Neisseria gonorrhoeae: identification of problem isolates by auxotyping, serotyping, and with a fluorescent antibody reagent.

GonoGen (Micro-Media Systems, Potomac, MD) is a commercially available coagglutination test for the identification of Neisseria gonorrhoeae. We tested 84 strains of Neisseria spp. and Branhamella catarrhalis, including 50 clinical isolates of N. gonorrhoeae. Eighty-six percent (51/59) of N. gonorrhoeae, including 86% (43/50) of clinical isolates of N. gonorrhoeae, were identified correctly in the GonoGen test. In contrast, all N. gonorrhoeae isolates reacted with a fluorescent antibody research reagent composed of monoclonal antibodies. Both reagents were specific for N. gonorrhoeae. Clinical isolates were classified by auxotyping and were serotyped with research monoclonal antibody reagents in coagglutination tests to characterize problem isolates; two auxotype/serovar classes, prototrophic/IA-4 and proline-requiring/IA-4, accounted for 71% (5/7) of GonoGen-negative clinical isolates. Five of the seven isolates that were missed with the first GonoGen lot we tested did react with a second lot of GonoGen reagent. Investigators from different cities in the U.S. have reported different rates of success with GonoGen. Our results indicate that certain N. gonorrhoeae serovars may account for the difference in performance observed with serological tests.