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Material Safety Data Sheet

Organisms

Organisms in the Clinical sector this product works with:

Dehydrated Culture Media

Sector: Clinical

DCLS AGAR

Code: CM0393

A modified DCA containing sucrose to improve the accuracy of recognition of pathogenic enterobacteriaceae.

Typical Formula*

gm/litre

Special peptone

10.0

Sodium citrate

10.5

Sodium thiosulphate

5.0

Lactose

5.0

Sucrose

5.0

Sodium desoxycholate

2.5

Neutral red

0.03

Agar

12.0

pH 7.2 ± 0.2 @ 25°C

* Adjusted as required to meet performance standards 

Directions
Suspend 50g in 1 litre of distilled water. Bring to the boil to dissolve the medium. Cool to 50°C and pour into sterile Petri dishes.
DO NOT AUTOCLAVE.

Description
DCLS Agar is a modified form of Desoxycholate Citrate Agar1 which includes sucrose in its formulation. The addition of this fermentable carbohydrate increases the usefulness of the medium because non-pathogenic sucrose-fermenting organisms may be recognised by their red colonies, e.g. some Proteus, Enterobacter and Klebsiella species.

DCLS Agar reduces the number of false-positive sub-cultures when picking colonies and therefore improves the efficiency of isolation.
The Special peptone, used in DCLS Agar, includes the nucleic acid factors, vitamins and carbon compounds of meat extract, as well as a rich variety of polypeptides. It has improved the growth of shigellae and salmonellae, but it should be noted that Shigella sonnei may exhibit a translucent, pink colony which should not be confused with the red Escherichia coli colony.

The selectivity of DCLS Agar is similar to Desoxycholate Citrate Agar and it will grow Vibrio species, as well as salmonellae and shigellae, whilst inhibiting the growth of Escherichia coli.

DCLS Agar may be inoculated directly from the specimen, or inoculated after enrichment through Selenite Broth CM0395 and LP0121, Muller-Kauffmann Tetrathionate Broth CM0343 or Tetrathionate Broth CM0029. The plates should be incubated overnight (18-24 hours) at 35°C and examined for the presence of pale, translucent or colourless colonies. Sub-cultures can be made into confirmatory media such as Kligler Iron Agar CM0033 or Triple Sugar Iron Agar CM0277 or picked for transfer to nutrient broth for subsequent motility tests and serological agglutinations.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared agar plates at 2-8°C.

Appearance
Dehydrated medium: Straw / pink coloured, free-flowing powder
Prepared medium: Red coloured gel

Quality control

Positive controls:

Expected results

Lactose/sucrose fermenters 
Escherichia coli ATCC® 25922 *

Reduced growth; pink coloured colonies

Non-lactose/sucrose fermenters 
Salmonella typhimurium ATCC® 14028*Good growth; translucent colonies

Negative control:

 
Staphylococcus aureus ATCC® 25923*

No growth

* This organism is available as a Culti-Loop®

Precautions
Boil the medium for the minimal period of time to get the agar into solution. Overheating reduces the agar gel strength and increases the degree of inhibition. It is therefore important not to hold the molten medium at 50°C for more than the short time required to distribute it into dishes.

Reference
1. Leifson E. (1935) J. Path. Bact. 40. 581-599.

 
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