Cystine tryptic agar

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Cystine tryptic agar (CTA), also known as cystine trypticase agar,[1][2] is a growth medium used for the identification of microorganisms.[3]

It can be used to determine if organisms can ferment various carbohydrates, including maltose, lactose, and sucrose. This approach can be used to type organisms because although strains quickly gain antibiotic resistance, they rarely gain the ability to metabolize new nutrients (though exceptions are known.) For example, the following fermentation patterns have been observed:

Organism Fermentable sugars
Neisseria gonorrhoeae glucose[4]
Neisseria meningitidis glucose, maltose[4]
Neisseria lactamica glucose, maltose, lactose[4]
Neisseria mucosa glucose, maltose, sucrose[4]
Moraxella catarrhalis none of the major sugars[4]

Typical composition[edit]

Cystine tryptic agar typically contains (w/v):[5]

See also[edit]


  1. ^ "BSCI424 Laboratory Media". Retrieved 2008-11-17.
  2. ^ Hollis DG, Wiggins GL, Weaver RE (January 1969). "Neisseria lactamicus sp. n., a lactose-fermenting species resembling Neisseria meningitidis". Appl Microbiol. 17 (1): 71–7. PMC 377615. PMID 4975454.
  3. ^ "University of Wisconsin - Madison, Veterinary Mycology". Archived from the original on 2008-11-24. Retrieved 2008-11-17.
  4. ^ a b c d e "Acid Detection Test- Gonorrhea - STD information from CDC".
  5. ^ Becton, Dickinson and Company, CTA Medium, 2005.