Correlation of cell-envelope phenotypes of Neisseria gonorrhoeae with site of infection and serogroup.

The envelope phenotypes and coagglutination (CoA) W serogroups of 301 unselected clinical isolates of Neisseria gonorrhoeae were studied. Of the 287 isolates from infections acquired in the Edinburgh area, 252 (88%) were of the wild-type phenotype, 17 (6%) were of Env phenotype with increased permeability of the cell envelope, and 18 (6%) were of Mtr phenotype with reduced permeability of the cell envelope. Mtr strains were isolated significantly more often from homosexual men than from heterosexual men and women (p less than 0.001). Of the isolates from homosexual men there were considerably fewer Mtr phenotypes among rectal isolates than among urethral and throat isolates. All isolates from homosexual men, 57% from heterosexual men and 52% from women were of CoA serogroup WII (including WII/WIII). Although the Mtr phenotype was strongly associated with serogroup-WII isolates from homosexual men, there was no such correlation between the Mtr phenotype and serogroup-WII isolates from heterosexual patients. It is suggested that hydrophobic compounds in the rectal environment are not the major factor in selecting serogroup-WII strains of Mtr phenotype associated with homosexually acquired infection. The hypothesis that the Mtr phenotype and serogroup WII are selected independently as a result of a more general selective pressure such as antibiotic usage, common to all infected sites, is discussed.