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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

Code: CM0301

Recommended for diagnostic urinary bacteriology. The medium supports the growth of all urinary potential pathogens giving good colonial differentiation and clear diagnostic 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

Agar

15.0

pH 7.3 ± 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
A dehydrated Cystine-Lactose-Electrolyte Deficient (CLED) medium made to the formula described by Mackey and Sandys1 as a modification for urinary bacteriology of the Electrolyte Deficient Medium developed by Sandys2.

This medium is recommended for urinary bacteriology, supporting the growth of all urinary pathogens and giving good colonial differentiations and clear diagnostic characteristics. The presence of important contaminants such as diphtheroids, lactobacilli and micrococci is also clearly elicited, giving an indication of the degree of contamination.

In the laboratory CLED Medium provides a valuable non-inhibitory diagnostic agar for plate culture of urinary organisms. It is electrolyte deficient to prevent the swarming of Proteus species.

The medium has been used successfully in the Dip-inoculum Transport Medium technique ( Mackey and Sandys1,3 ).

A variant of this technique has been described by Guttman and Naylor4 who employed media-coated slides.

These techniques overcome false bacteriological results associated with delay in the transport of the specimens of urine to the laboratory and permit a clinically accurate routine differential viable count. They are, therefore, suitable for both general practitioner and hospital work including the screening of ante-natal specimens for symptomless bacteriuria.

For full details, the original papers should be consulted.

Growth Characteristics on CLED Medium (18 hours incubation)

Escherichia coli

yellow, opaque colonies with a slightly deeper coloured centre about 1.25 mm diam. (Non-lactose fermenting strains - blue colonies

Klebsiella speciesextremely mucoid colonies varying in colour from yellow to whitish-blue
Proteus species translucent blue colonies usually smaller than Escherichia coli
Salmonella speciesflat blue colonies
Pseudomonas aeruginosagreen colonies with typical matt surface and rough periphery
Enterococcus faecalis yellow colonies about 0.5 mm diameter
Staphylococcus aureusdeep yellow colonies about 0.75 mm diameter, uniform in colour
Coagulase negative staphylococci pale yellow or white, more opaque than Enterococcus faecalis, often with paler periphery
Corynebacteria very small grey colonies
Lactobacillisimilar to corynebacteria but with a rougher surface

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°Cand use before the expiry date on the label.
Store the prepared 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 vulgaris ATCC® 8427 *

Good growth; blue green translucent colonies

Proteus mirabilis ATCC®12453 * Good growth; blue colonies; no swarming
Staphylococcus aureus ATCC® 25923 *

Good growth; yellow colonies

Negative control:

 

Uninoculated medium

No change

* This organism is available as a Culti-Loop®

References
1. Mackey J. P. and Sandys G. H. (1966) B.M.J. 1. 1173.
2. Sandys G. H. (1960) J. Med. Lab. Techn. 17. 224.
3. Mackey J. P. and Sandys G. H. (1965) B.M.J. 2. 1286-1288.
4. Guttman D. and Naylor G. R. E. (1967) B.M.J. 2. 343-345.

 
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