Dehydrated Culture Media

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`LAB-LEMCO’ AGAR

Code: CM0017

A nutrient agar for general bacteriological use, it may be used as the basis for selective, differential, or enriched media.

Typical Formula*

gm/litre

`Lab-Lemco’ powder

3.0

Peptone

5.0

Agar

15.0

pH 7.4 ± 0.2 @ 25°C

 
* Adjusted as required to meet performance standards

Directions
Suspend 23g in 1 litre of distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes.

Description
`Lab-Lemco’ Agar is a general purpose medium used for the examination of water and dairy products1,2.

t is used as a nutrient meat extract agar for general bacteriology and for the preservation of stock cultures. The absence of sodium chloride in the formulation prevents Proteus mirabilis forming `swarming’ colonies.

When used as a basal medium, other substances can be added to produce selective, differential or enriched media.

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 at 2-8°C.

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

Quality control

Positive controls:

Expected results

Staphylococcus aureus ATCC® 25923 *

Good growth; straw coloured colonies

Escherichia coli ATCC® 25922 *

Good growth; straw coloured colonies

Negative control:

 

Uninoculated medium

No change

* This organism is available as a Culti-Loop®

Precautions
`Lab-Lemco’ Agar is slightly more alkaline than the medium used in the APHA publications (pH 6.8).
If blood is to be added to the agar then it is necessary to add sodium chloride (0.5% w/v) to prevent haemolysis.

References
1. American Public Health Association (1980) Standard Methods for the Examination of Water and Wastewater. 15th Edn. APHA Inc. Washington DC.
2. American Public Health Association (1978) Standard Methods for the Examination of Dairy Products. 14th Edn. APHA Inc. Washington DC.

 
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