These were two culture plates used to grow colonies of Neisseria gonorrhoeae bacteria.

Known as "overgrowth", note that the "non-selective" chocolate agar medium on the left, due to its composition, allowed for the growth of organismal colonies other than those of Neisseria gonorrhoeae, while the selective Thayer-Martin medium on the right, containing antimicrobials that inhibit the growth of organisms other than N. gonorrhoeae ; vancomycin inhibits gram-positive bacteria, colistin inhibits gram-negative bacteria including the commensal Neisseria spp., trimethoprim inhibits swarming of Proteus spp., nystatin (an antifungal agent).

Text: CDC/PHIL