Direct detection of Neisseria gonorrhoeae with monoclonal antibodies characterized by serotyping reagents

A panel of monoclonal antibodies (MAbs) directed to outer membrane protein I were generated with the ultimate aim of detecting Neisseria gonorrhoeae in patient samples by a direct immunofluorescence (IF) test. In an initial evaluation of the sensitivity of these reagents, a cocktail of six IF MAbs recognized 491 (91%) of 540 gonococci isolates from several centers in Sydney, Australia. IF MAbs designated 185 and 228 recognized serovars of WI serogroup and IF MAbs 208, 210, and 312 recognized serovars of WII/III serogroup. IF MAb 198 recognized serovars within both serogroups. Three additional IF MAbs, designated 322, 323, and 330, were then generated by using strains which failed to react with the original MAb cocktail and which belonged to particular serovars. The new cocktail of nine IF MAbs recognized 96% of the gonococcal isolates, which incidentally contained representatives of serovars shown to have a worldwide distribution in previous studies. Although subtle differences were apparent in the reaction patterns found with coagglutination (serotyping) and IF, there nonetheless seems to be merit in the approach of continually evaluating the sensitivity of diagnostic reagents such as MAbs. This is especially true with an organism such as N. gonorrhoeae, which has the capacity to regularly alter the antigenic structure of its outer membrane proteins.