Thayer–Martin agar (or Thayer–Martin medium, or VPN agar) is a

Mueller–Hinton agar Mueller Hinton agar is a type of growth medium used in microbiology to culture bacterial isolates and test their susceptibility to antibiotics. This medium was first developed in 1941 by John Howard Mueller and Jane Hinton, who were microbiologis ...

with 5% chocolate sheep blood and

antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

. It is used for culturing and primarily isolating pathogenic ''

Neisseria ''Neisseria'' is a large genus of bacteria that colonize the mucous membranes of many animals. Of the 11 species that colonize humans, only two are pathogens: '' N. meningitidis'' and '' N. gonorrhoeae''. ''Neisseria'' species are Gram-negative ...

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

, including ''

Neisseria gonorrhoeae ''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular) or ''gonococci'' (plural), is a species of Gram-negative diplococci bacteria first isolated by Albert Ludwig Sigesmund Neisser, Albert Neisser in 1879. An obligate human pathog ...

'' and ''

Neisseria meningitidis ''Neisseria meningitidis'', often referred to as the meningococcus, is a Gram-negative bacterium that can cause meningitis and other forms of meningococcal disease such as meningococcemia, a life-threatening sepsis. The bacterium is referred to a ...

'', 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 Chocolate agar (CHOC) or chocolate blood agar (CBA) is a nonselective, Growth medium#Enriched media, enriched growth medium used for isolation of pathogenic bacteria. It is a variant of the blood agar plate, containing red blood cells that have ...

is used. Thayer–Martin agar was initially developed in 1964, with an improved formulation published in 1966.

Components

It usually contains the following combination of antibiotics, which make up the VPN acronym: *

Vancomycin Vancomycin is a glycopeptide antibiotic medication used to treat certain bacterial infections. It is administered intravenously ( injection into a vein) to treat complicated skin infections, bloodstream infections, endocarditis, bone an ...

, which is able to kill most

Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. The Gram stain is ...

organisms, although some Gram-positive organisms such as ''

Lactobacillus ''Lactobacillus'' is a genus of gram-positive, aerotolerant anaerobes or microaerophilic, rod-shaped, non-spore-forming bacteria. Until 2020, the genus ''Lactobacillus'' comprised over 260 phylogenetically, ecologically, and metabolically div ...

'' and ''

Pediococcus ''Pediococcus'' is a genus of gram-positive lactic acid bacteria, placed within the family of Lactobacillaceae. They usually occur in pairs or tetrads, and divide along two planes of symmetry, as do the other lactic acid cocci genera '' Aerococc ...

'' are intrinsically resistant *

Polymyxin Polymyxins are antibiotics. Polymyxins B and E (also known as colistin) are used in the treatment of Gram-negative bacterial infections. They work mostly by breaking up the bacterial cell membrane. They are part of a broader class of molecul ...

, also known as colistin, which is added to kill most

Gram-negative Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists ...

organisms except ''Neisseria'', although some other Gram-negative organisms such as ''

Legionella ''Legionella'' is a genus of gram-negative bacteria, gram-negative bacteria that can be seen using a silver stain or grown in a special media that contains cysteine, an amino acid. It is known to cause legionellosis (all illnesses caused by ''Legi ...

'' are also resistant *

Nystatin Nystatin, sold under the brand name Mycostatin among others, is an antifungal medication. It is used to treat ''Candida (fungus), Candida'' infections of the skin including diaper rash, Candidiasis, thrush, esophageal candidiasis, and vaginal ...

, which can kill most

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

Trimethoprim Trimethoprim (TMP) is an antibiotic used mainly in the treatment of bladder infections. Other uses include for middle ear infections and travelers' diarrhea. With sulfamethoxazole or dapsone it may be used for ''Pneumocystis'' pneumonia ...

inhibits swarming of ''Proteus'' spp

Clinical implications

A negative culture on Thayer–Martin in a patient exhibiting symptoms of

pelvic inflammatory disease Pelvic inflammatory disease (PID), also known as pelvic inflammatory disorder, is an infection of the upper part of the female reproductive system, mainly the uterus, fallopian tubes, and ovaries, and inside of the pelvis. Often, there may be no ...

most likely indicates an infection with ''

Chlamydia trachomatis ''Chlamydia trachomatis'' () is a Gram-negative, Anaerobic organism, anaerobic bacterium responsible for Chlamydia infection, chlamydia and trachoma. ''C. trachomatis'' exists in two forms, an extracellular infectious elementary body (EB) and an ...

''.

References

Microbiological media {{Microbiology-stub