V-C-N Inhibitor is an antibiotic mixture of vancomycin, colistin and nystatin which is incorporated into culture media to permit selective isolation of Neisseria gonorrhoeae and N. meningitidis. V-C-N-T Inhibitor contains the same antibiotic mixture as V-C-N Inhibitor with the addition of trimethoprim to improve recovery of pathogenic Neisseria by increasing selectivity of isolation media.