ThayerMartin

Thayer-Martin agar is a selective culture medium used to isolate pathogenic Neisseria species, especially Neisseria gonorrhoeae and Neisseria meningitidis, from clinical specimens such as urethral, endocervical, pharyngeal, and rectal swabs, as well as cerebrospinal fluid. It is based on a chocolate agar or lysed red blood cell base enriched to support Neisseria growth, and it contains a combination of antibiotics—vancomycin, polymyxin B, and nystatin—to suppress contaminating bacteria and yeasts. Additional agents, such as trimethoprim in Modified Thayer-Martin formulations, may be included to broaden the spectrum of inhibition against extraneous flora and some commensal Neisseria.

Named for its developers, Thayer and Martin, the medium was introduced in the 1960s to improve selective isolation of Neisseria gonorrhoeae from mixed clinical specimens.

Variants include Modified Thayer-Martin (MTM), which adds trimethoprim, and VPN (vancomycin, polymyxin B, nystatin). The medium is widely used in clinical laboratories for initial isolation, followed by confirmatory identification and antimicrobial susceptibility testing. While effective at suppressing many competing organisms, Thayer-Martin can still fail to recover certain strains, and results require subsequent biochemical or molecular confirmation to identify Neisseria species and to distinguish pathogenic Neisseria from non-pathogenic flora.