Thayer-Martin agar (or Thayer-Martin medium, or VPN agar) is a Mueller-Hinton agar containing 5% chocolate sheep blood and antibiotics. It is used for the culture and primarily isolation of the pathogenic bacteria Neisseria, including Neisseria gonorrhoeae and Neisseria meningitidis, because the medium inhibits the growth of most other microorganisms. Thayer Martin Agar contains nitrogenous nutrients in the form of casein and meat peptones, which neutralize toxic fatty acids that may be present in the agar. Hemoglobin provides factor X (hemin) for Haemophilus species. Growth complement is a defined complement that provides factor V (nicotinamide adenine dinucleotide, NAD) for Haemophilus species and vitamins, amino acids, co-enzymes, dextrose, ferric ion and other factors that enhance the growth of pathogenic Neisseria. This selective medium contains antimicrobial agents, vancomycin, colistin and nystatin (V-C-N inhibitor) to suppress normal flora. Vancomycin is mainly active against gram-positive bacteria. Colistin inhibits Gram-negative bacteria, including Pseudomonas species, but is not active against Proteus species. Nystatin inhibits fungi.