Changes in the prevalence of auxotypes of Neisseria gonorrhoeae among black and white patients attending a clinic for sexually transmitted diseases.

Before 1978, isolates of Neisseria gonorrhoeae from white patients attending a venereal disease clinic were more susceptible to penicillin G than were isolates from black patients, because the whites were more frequently infected with the Arg- Hyx- Ura- auxotype that was highly susceptible to penicillin. Recent isolates from the same clinic show a change both in the auxotypes and in the penicillin susceptibility of N. gonorrhoeae infecting the two patient groups. Of 211 isolates studied in 1978, the four most common auxotypes were, in decreasing frequency: Pro-, nonrequiring, Arg- Hyx- Ura- and Arg-. In the present study of 265 isolates, the order of frequency was nonrequiring; Pro-; Pro- Arg-(Orn*) Ura-; and Arg- Hyx- Ura-. The Pro- Arg-(Orn*) Ura- auxotype was new to the clinic and was significantly more frequent in white than in black patients and significantly more resistant to penicillin than were gonococci of the remaining auxotypes. With the appearance of the Pro- Arg-(Orn*) Ura- auxotype among white patients, there was no significant difference in the susceptibility to penicillin of isolates of N. gonorrhoeae from the two groups of patients.