Thayer-Martin medium is a selective culture medium designed to isolate Neisseria species, especially Neisseria gonorrhoeae. It uses a chocolate agar base enriched for Neisseria growth and includes antibiotics such as vancomycin to suppress Gram-positive bacteria, colistin to inhibits many Gram-negative rods, and nystatin to prevent fungal growth. This combination reduces competing flora found in clinical specimens, allowing Neisseria gonorrhoeae to grow when present. Neisseria gonorrhoeae is a fastidious Gram-negative diplococcus that causes gonorrhea, so this selective medium is particularly useful for recovering it from samples like urethral or cervical swabs. The other organisms listed are typically inhibited by these antibiotics, so they would not be favored growth on this medium.