In vitro antigonococcal activity of urogenital coagulase-negative staphylococci

Twenty-four urogenital isolates of coagulase-negative staphylococci were selected because of their demonstrated ability to inhibit Neisseria gonorrhoeae growth in vitro. These organisms showed quantitative differences in their growth-interfering capability as revealed by a flip-flop agar overlay method. The composition of the culture medium affected the production of antigonococcal activity. Antigonococcal activity was shown with the following media: GC agar base with Lankford defined supplement, brain heart infusion agar, trypticase soy agar, and dextrose starch agar, but not with the GC agar base with CVA enrichment. An antigonococcal activity was obtained in the liquid phase prepared from semisolid agar cultures for 10 of the 24 staphylococcal isolates, whereas no activity was found in the supernatant from liquid cultures. The production of antigonococcal activity by staphylococci in vitro is influenced by growth conditions.