Association of auxotypes of Neisseria gonorrhoeae and susceptibility to penicillin G, spectinomycin, tetracycline, cefaclor, cefoxitin, and moxalactam.

Isolates of Neisseria gonorrhoeae from 304 patients attending a venereal disease clinic were examined by a plate dilution method for their susceptibility to six antibiotics: penicillin G, spectinomycin, tetracycline, cefaclor, cefoxitin, and moxalactam. The isolates were also characterized by gonococcal auxotyping. The most frequent auxotypes were Nonrequiring, 58%; Pro-, 14%; Pro- Arg (Orn*) Ura-, 14%; Arg- Hyx- Ura-, 6%; and a miscellaneous group consisting of 8% of the isolates. If the entire group of isolates were examined, moxalactam was the most active of the antibiotics; 94% of the isolates were inhibited by less than or equal to 0.25 microgram/ml. The Pro- Arg (Orn*) Ura- isolates were relatively resistant to penicillin G and cefoxitin. The Arg- Hyx- Ura- group of isolates was the most susceptible of the auxotypes to all of the antibiotics except spectinomycin. The uncommon auxotype Arg (Orn*) Ura- has a requirement for arginine that is satisfied by citrulline but not by ornithine. The results of the present study indicate that the nutritional requirements of gonococci may be associated with their response to certain antibiotics.