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Material Safety Data Sheet

Organisms

Organisms in the Clinical sector this product works with:

Dehydrated Culture Media

Sector: Clinical

CLED MEDIUM (WITH ANDRADE INDICATOR)

Code: CM0423

A modification of the CLED Medium of Mackey and Sandys1 containing Andrade Indicator to enhance the differentiation of colony characteristics.

Typical Formula*

gm/litre

Peptone

4.0

`Lab-Lemco’ powder

3.0

Tryptone

4.0

Lactose

10.0

L-cystine

0.128

Bromothymol blue

0.02

Andrade Indicator

0.1

Agar

15.0

pH 7.5 ± 0.2 @ 25°C

 
* Adjusted as required to meet performance standards 

Directions
Suspend 36.2g in 1 litre of distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes. Mix well before pouring.

Description
The formula for this medium is similar to that for CLED Medium, CM0301, but with the addition of acid fuchsin which enhances the colonial appearance and aids in identification of the organisms. The colour of the medium differs from that of the standard medium at various pH levels.
Bevis2 listed the pH and colour as follows:

pH

Colour of Medium

7.4

Deep blue

7.0

Blue grey

6.8

Pale slate grey

6.6

Pinkish grey

6.4

Bright red with slight smokey tint

6.0

Bright red

The medium should not be incubated for longer than 24 hours since, if lactose fermenters predominate, the whole of the medium may turn pink, masking the presence of non-lactose fermenters.

Colonial Characteristics
Escherichia coli
- Bright pink semi-translucent colonies with a surrounding pink halo in the medium.
Proteus mirabilis - Blue-green translucent colonies.
Klebsiella aerogenes - Grey-green mucoid colonies.
Aeromonas anitratus - Small, grey-green, translucent colonies.
Staphylococcus aureus - Smooth, entire, opaque; bright golden yellow colonies. Lactose fermenting.
Staphylococcus albus - Smooth, entire, opaque porcelain white or very pale pink colonies.
Enterococcus faecalis - Similar to Staph. aureus but smaller and a much deeper orange yellow colour.
Streptococcus pyogenes - Small opaque grey-green colonies.
Furniss et al.3 describe the use of CLED Medium with Andrade’s Indicator for rapidly distinguishing vibrios into halophilic and non-halophilic groups. Non-halophilic vibrios grow; halophilic vibrios do not.

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 plates of medium at 2-8°C.

Appearance
Dehydrated medium: Pale green coloured, free-flowing powder
Prepared medium: Blue green coloured gel

Quality control

Positive controls:

Expected results

Proteus mirabilis ATCC® 12453 * Good growth; blue colonies; no swarming
Proteus vulgaris ATCC® 8427 *

Good growth; blue green translucent colonies

Staphylococcus aureus ATCC® 25923 *

Good growth; yellow orange colonies with pink halo

Negative control:

 

Uninoculated medium

No change

* This organism is available as a Culti-Loop®

Precautions
Note the incubation time limit of 24 hours if lactose-fermenting colonies present.
Shigella species may not grow on electrolyte-deficient medium.

References
1. Mackey J.P. and Sandys G.H. (1966) B.M.J. 1. 1173
2. Bevis T. D. (1968) J. Med. Lab. Technol. 25. 38-41.
3. Furniss A. L., Lee J. V. and Donovan T. J. (1978) P.H.L.S. Monograph series, London, H.M.S.O., 11.

 
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