Modified Thayer Martin Medium Base (w/o Supplement) is recommended for selective isolation and enumeration of Neisseria species especially Neisseria gonorrhoeae. Addition of lysed blood after heating supplies vitamins, amino acids, coenzymes etc. which enhances the growth of pathogenic Neisseria. Vancomycin and colistin methane sulphate inhibit gram-positive and gram-negative bacteria respectively. On this medium, colonies of Neisseria gonorrhoeae appear small, grayish white to colorless, mucoid and Neisseria meningitidis colonies appear as medium to large, blue gray and mucoid in appearance.