DCA agar (
deoxycholate citrate
Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the ...
agar) is a solid bacteriological
growth medium used for isolation of enteric pathogens.
Uses
It is particularly useful for the isolation of organisms that cause bacillary
dysentery
Dysentery (UK pronunciation: , US: ), historically known as the bloody flux, is a type of gastroenteritis that results in bloody diarrhea. Other symptoms may include fever, abdominal pain, and a feeling of incomplete defecation. Complications ...
,
salmonella strains that cause
food poisoning and
''Salmonella'' Paratyphi. It is not so selective for ''Salmonella'' Typhi. This
growth medium is inhibitory to most gut bacteria, in particular species of the genus ''
Proteus
In Greek mythology, Proteus (; Ancient Greek: Πρωτεύς, ''Prōteus'') is an early prophetic sea-god or god of rivers and oceanic bodies of water, one of several deities whom Homer calls the "Old Man of the Sea" ''(hálios gérôn)''. ...
'', although these species do survive on DCA agar. It is therefore essential that suspected pathogens must be subcultured on a less inhibitory medium prior to identification.
''Salmonella spp'' appear to be yellow or colourless colonies, often with a dark centre.
As there are many bacteria that also look like Salmonella on DCA, it is widely recommended that more selective agars are used for the identification of ''Salmonella'', namely xylose lysine deoxycholate (XLD) agar.
This growth medium is heat-sensitive and should be poured and cooled as soon as possible after addition of the deoxycholate, otherwise it tends to become very soft and difficult to handle. It has a
pH of approximately 7.3, and when poured and cooled, appears light to dark pink in colour.
Contents
One liter of deoxycholate citrate agar contains:
[
]
References
{{DEFAULTSORT:Dca Agar
Microbiological media