Auxotypes of Neisseria gonorrhoeae isolated from heterosexual men, homosexual men, and heterosexual women.

During 1979-1984 we auxotyped 1822 strains of Neisseria gonorrhoeae and recorded the site of isolation and sexual orientation of the patients. Auxotypes were determined by the growth requirements of strains for proline (Pro-), uracil (Ura-), hypoxanthine (Hyx-), citrulline (Cit-), or citrulline replaceable by ornithine (Orn-). Of all isolates from homosexual men, 96% belonged to three auxotypes: nonrequiring (NR), Pro-, or Orn-, and only 1.5% belonged to the Pro-, Cit-, Ura- and Orn-, Ura-, Hyx- auxotypes. Of the isolates from women, 49.9% belonged to these latter two auxotypes. Of the strains isolated from male homosexuals, 19.5% were resistant to 1.0 microgram of erythromycin/ml, whereas only 9.6% of strains from other men and 2.6% of strains from women were resistant to this concentration. We suggest that strains of N. gonorrhoeae infecting homosexual men tend to be less demanding in their nutritional requirements and more resistant to erythromycin than strains infecting heterosexual men and women.