Thayer Martin agar

Updated on Nov 11, 2023

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Thayer-Martin agar (or Thayer-Martin medium) is a Mueller-Hinton agar with 5% chocolate sheep blood and antibiotics. It is used for culturing and primarily isolating pathogenic Neisseria bacteria, including Neisseria gonorrhoeae and Neisseria meningitidis, as the medium inhibits the growth of most other microorganisms. When growing Neisseria meningitidis, one usually starts with a normally sterile body fluid (blood or CSF), so a plain chocolate agar is used. Thayer-Martin agar was initially developed in 1964, with an improved formulation published in 1966.

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Components

It usually contains the following combination of antibiotics, called VCN inhibitor

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Vancomycin, which is able to kill most Gram-positive organisms, although some Gram-positive organisms such as Lactobacillus and Pediococcus are intrinsically resistant

Colistin, which is added to kill most Gram-negative organisms except Neisseria, although some other Gram-negative organisms such as Legionella are also resistant

Nystatin, which can kill most fungi

Trimethoprim, which inhibits Gram-negative organisms, especially swarming Proteus

Clinical implications

A negative culture on Thayer-Martin in a patient exhibiting symptoms of pelvic inflammatory disease most likely indicates an infection with Chlamydia trachomatis.

Thayer-Martin agar Free picture brucella melitensis bacteria grown modified thayer

Thayer-Martin agar Media at University of Wisconsin Milwaukee StudyBlue

References

Thayer-Martin agar Wikipedia

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Contents

Components

Clinical implications

References