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Dehydrated Culture Media

NUTRIENT BROTH NO.2

Code: CM0067

A nutritious medium suitable for the cultivation of fastidious pathogens and other micro-organisms.

Typical Formula*

gm/litre

`Lab-Lemco’ powder

10.0

Peptone

10.0

Sodium chloride

5.0

pH 7.5 ± 0.2

 
* Adjusted as required to meet performance standards

Directions
Add 25g to 1 litre of distilled water. Mix well, distribute into final containers and sterilise by autoclaving at 121°C for 15 minutes.

Directions (to prepare Preston Campylobacter Selective Enrichment Broth)
Dissolve 12.5g of Nutrient Broth No.2 in 475ml of distilled water and sterilise by autoclaving at 121°C for 15 minutes. Cool to 50°C or below. Aseptically add 25ml of Lysed Horse Blood SR0048, 1 vial of Preston Campylobacter Selective Supplement SR0117 or SR0204 and 1 vial of Campylobacter Growth Supplement  SR0232. Aseptically dispense 5ml volumes in sterile small screw-capped bottles. The Selective Enrichment Broth may be stored for up to 7 days at 2-8°C.

It is essential that the head space above the liquid should be as small as possible to ensure microaerobic conditions.

Description
This medium is comparable to a meat infusion and is richer in nutrients than Nutrient Broth CM0001. It gives good growth from small inocula and is recommended for sterility testing for aerobic organisms. Nutrient Broth No.2 complies with the recommendations in the `British Pharmacopoeia’1 for the composition of a sterility testing medium for aerobes. The medium is ideally suited for sub-culture, particularly as a secondary growth medium for staphylococci which are to be tested for coagulase production. Nutrient Broth No.2 made up at double strength corresponds to the medium recommended by the British Standards Institution 2 for use in the determination of the Rideal-Walker Coefficient of Disinfectants.

Nutrient Broth No.2 is the basal medium for Preston Campylobacter Enrichment Broth 3,4.

Selective enrichment broth technique
1. Prepare the Preston Selective Enrichment Broth as directed from CM0067, SR0117, or SR0232 and Lysed Blood (SR0048).
2. Emulsify the specimen under test in the selective enrichment broth.
3. Incubate the broth aerobically at 42°C for 24 hours.
4. Subculture on to Preston Campylobacter Selective Agar or Campylobacter Blood-Free Selective Agar.

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 medium at 2-8°C.

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

Quality control

Positive controls:

Expected results

Staphylococcus aureus ATCC® 25923 *

Turbid growth

Pseudomonas aeruginosa ATCC® 27853 *Turbid growth

Negative control:

 

Uninoculated medium

No change

Campylobacter Media 

Positive control:

Expected results

Campylobacter jejuni ATCC® 29428 *

Good growth; grey-brown coloured colonies

Negative control:

 

Escherichia coli ATCC® 25922 *

Inhibited

* This organism is available as a Culti-Loop®

References
1. British Pharmacopoeia (1980) London HMSO.
2. British Standard 541: (1934) `Determining the Rideal Walker Coefficient of Disinfectants’ BSI London, p.9.
3. Bolton F. J. and Robertson L. (1982) J. Clin. Pathol. 35. 462-467.
4. Bolton F. J., Coates D. and Hutchinson D. N. (1984) J. Appl. Bact. 56. 151-157.

 
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