Resistance to the complement-dependent bactericidal activity of normal human serum is found in nearly all Neisseria gonorrhoeae strains causing disseminated gonococcal infection. Transformation of serum-sensitive gonococcal strain NRL 7189 to serum resistance using deoxyribonucleic acid from three separate disseminated-infection gonococci was accompanied by simultaneous structural and antigenic changes in the principal outer-membrane protein (POMP) of the transformants. In each of 10 separate transformations, there was a reduction in subunit molecular weight of the POMP from that in the recipient (39,000) to that in the deoxyribonucleic acid donors (36,500). Also, in each instance the POMP antigenic type, as measured by enzyme-linked immunosorbent assay, converted from that of the recipient to an antigenic type common to each DGI donor strain. This conversion of POMP antigen was reflected in part by changes in the surface fluorescence of the transformed gonococci to the microimmunofluorescence pattern of the donor strains. These results suggested that serum resistance of gonococci is related to the possession of a POMP of characteristic subunit molecular weight and antigenicity.

Principal outer membrane protein (protein I) of Neisseria gonorrhoeae was prepared nearly free of lipopolysaccharide (LPS) and substantially purified from other membrane proteins by chromatography of partially purified gonococcal outer membranes over Sepharose 6B in the presence of deoxycholate at pH 9.0. This protein I of nine separate antigenic types was coated to polystyrene tubes and used in the enzyme-linked immunosorbent assay (ELISA) to measure antibody to protein I or in inhibition tests to quantitate protein I antigen. No significant inhibition of the ELISA test was produced by purified LPS from the strain used to prepare each of the protein I types or by whole gonococci bearing the same LPS but different protein I antigens as the strain used to produce a given protein I antigen. Of 125 strains of gonococci used as whole organisms to inhibit the protein I ELISA, 124 (99%) typed with one or more of the nine protein I types, and 35% of these typed with a single protein I serotype. Sixty-one of 65 (94%) strains from Seattle and Atlanta patients with disseminated gonococcal infection contained protein I serotype 1, and 16 of 24 (64%) strains from Seattle patients with salpingitis bore one or both of protein I serotypes 1 and 2.

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This study was undertaken to determine if the categorization of Neisseria gonorrhoeae strains into disseminated gonococcal infection (DGI) and non-DGI types was also paralleled by some common characteristic in their penicillinbinding proteins (PBPs [MIC], c0.03 ,ug/ml), (iii) require arginine, hypoxanthine, and uracil for their growth (12), and (iv) can compete highly efficiently for iron (9). It was also demonstrated that serum resistance is associated with the possession of a principal outer membrane protein (POMP) of characteristic subunit molecular weight and antigenicity (5). The differential penicillin susceptibility of isolates from uncomplicated and disseminated gonococcal infections (DGI and non-DGI) led us to speculate that the DGI character might also be paralleled by the presence or absence of some specific penicillinbinding proteins (PBPs) in the inner membrane of N. gonorrhoeae. We have, therefore, used techniques similar to those described by Spratt (13) munosorbent assay, was performed using purified gonococcal POMP from strain 7122 as described earlier (2, 4, 5). The serum bactericidal activities and auxotyping (5, 6, 11) of the N. gonorrhoeae strains used were performed in the laboratories of K.