TRIPLE SUGAR IRON AGAR

Code: CM0277

a composite medium for the differentiation of Enterobacteriaceae by three sugar fermentations and hydrogen sulphide production

Typical Formula*	gm/litre
`Lab-Lemco’ powder	3.0
Yeast extract	3.0
Peptone	20.0
Sodium chloride	5.0
Lactose	10.0
Sucrose	10.0
Glucose	1.0
Ferric citrate	0.3
Sodium thiosulphate	0.3
Phenol red	0.024
Agar	12.0
pH 7.4 ± 0.2 @ 25°C

* Adjusted as required to meet performance standards

Directions
Suspend 65g in 1 litre of distilled water. Bring to the boil to dissolve completely. Mix well and distribute. Sterilise by autoclaving at 121°C for 15 minutes. Allow the medium to set in sloped form with a butt about 1 in.deep.

Description
A composite medium for the differentiation of Enterobacteriaceae according to their ability to ferment lactose, sucrose and glucose, and to produce hydrogen sulphide.

Not only does this medium perform most of the functions of Kligler Iron Agar but, in addition, its sucrose content permits the recognition and exclusion of sucrose-fermenting species. These organisms may ferment lactose slowly or not at all during the incubation period, but they attack sucrose readily. Some Proteus and other species may give similar reactions to salmonellae and shigellae and it is necessary to distinguish them by their ability to hydrolyse urea. For this reason Triple Sugar Iron Agar should be used in parallel with Urea Broth or Urea Agar.

This medium was formerly considered to be interchangeable with Kligler medium for the detection of hydrogen sulphide producing Enterobacteriaceae. It is now thought that Triple Sugar Iron Agar is not suitable for the detection of hydrogen sulphide production by sucrose-fermenting organisms, such as some Citrobacter and Proteus species, in which the sucrose fermentation masks the hydrogen sulphide indicator in the medium ^†1.

Triple Sugar Iron Agar is recommended for the presumptive identification of colonies or sub-cultures from plating media such as Salmonella Shigella Agar (Modified) (CM0533), Bismuth Sulphite Agar (CM0201), Brilliant Green Agar (CM0263), MacConkey Agar No.3 (CM0115), or Desoxycholate Citrate Agar (Hynes) (CM0227).