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Dehydrated Culture Media

Sector: Clinical

ANAEROBE BASAL AGAR

Code: CM0972

A nutrient agar for the growth of anaerobic micro-organisms, particularly Bacteroides spp. and other fastidious anaerobes.

Typical Formula*

gm/litre

Peptone

16.0

Yeast extract

7.0

Sodium chloride

5.0

Starch

1.0

Dextrose

1.0

Sodium pyruvate

1.0

Arginine

1.0

Sodium succinate

0.5

L-cysteine HCl

0.25

Sodium bicarbonate

0.4

Ferric pyrophosphate

0.5

Haemin

0.005

Vitamin K

0.0005

Dithiothreitol

0.25

Agar

12.0

pH 6.8 ± 0.2 @ 25°C

 

* Adjusted as required to meet performance standards 

Directions
Suspend 46g in 1 litre of distilled water. Sterilise by autoclaving at 121°C for 15 minutes. Cool to 50-55°C and aseptically add 5-10% sterile Defibrinated Horse Blood SR0050.

Mix well and pour into sterile Petri dishes.

Description
Anaerobe Basal Agar contains peptones, carefully selected to support good growth of anaerobic bacteria and yeast extract as a vitamin source. Starch is present to absorb any toxic metabolites1. Sufficient arginine is added to ensure the growth of Eubacterium lentum2, whilst haemin and vitamin K are growth factors required by many Bacteroides species3. Haemin is also required by Porphyromonas species. Sodium succinate improves the growth of Prevotella melaninogenica and Bacteroides species4. Sodium pyruvate is added as an energy source for asaccharolytic cocci such as Veillonella. It also acts similarly to catalase and degrades traces of hydrogen peroxide, which may be produced by the action of molecular oxygen on media components5. L-cysteine hydrochloride and dithiothreitol are reducing agents, and cysteine has also been shown to stimulate the growth of some anaerobes6.

Technique
Inoculate the medium by surface plating to obtain single colonies. Incubate anaerobically for up to 5 days at 37°C. Anaerobic conditions can be achieved using the Oxoid AnaeroGen Atmosphere Generation System AN0025 with the Oxoid AnaeroJar AG0025.

The medium may be rendered selective for Gram-negative anaerobes by the addition of G-N supplement SR0108 and for non-sporing anaerobes by the addition of N-S supplement SR0107 with Tween 80. Neomycin Selective Supplement SR0163 can be added to select for Clostridia.

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 for upto 3 weeks at 2-8°C.

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

Quality control

Positive controls:

Expected results

Peptostreptococcus anaerobius ATCC® 27337 *Good growth; grey coloured colonies
Prevotella melaninogenica ATCC® 25845 *Good growth; grey coloured colonies

Clostridium perfringens ATCC® 13124

Good growth; grey coloured colonies

Negative control:

 
Uninoculated mediumNo change
* This organism is available as a Culti-Loop®

References
1. Ajello GW. Geely JC. Hayes PS. et al. Trans-isolate medium: a new medium for primary culturing and transport of Neisseria meningitidis, Streptococcus pneumoniae and Haemophilus influenzae. J. Clin. Micro. 1984:20:55-8.
2. Sperry JF. Wilkins TD. Arginine, a growth-limiting factor for Eubacterium lentum. J. Bacteriol 1976:127:780-4.
3. Gibbons RJ. and MacDonnald JB. Haemin and vitamin K compounds as required factors for the cultivation of certain strains of Bacteroides melaninogenicus. J. Bact. 1960:80:164-170.
4. Lev M. Keudell KC. and Milford AF. Succinate as a growth factor for Bacteroides melaninogenicus. J. Bact. 1971:108:175-8.
5. Neilson PA. Role of reduced sulphur compounds in nutrition of Proprionobacterium acnes. J. Clin. Micr. 1983:17:276-9.
6. Shanson DC. and Singh J. Effect of adding cysteine to brain-heart infusion broth on the isolation of Bacteroides fragilis from experimental blood cultures. J. Clin. Path. 1981:34:221-3.

 
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