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AZIDE DEXTROSE BROTH
Selective medium for the detection of Enterococci in water and sewage.
Typical formula g/l
15.0 Beef extract 4.5 Glucose 7.5 Sodium chloride
Sodium azide 0.2
Final pH 7.2 +/-0.2
Suspend 34.7g of Azide Dextrose Broth in 1000 ml of cold distilled water. Heat gently to dissolve, distribute into 10ml tubes and sterilise by autoclaving at 121°C for 15 minutes. For inocula of more than 1ml per 10ml medium prepare Azide Dextrose Broth at double or multiple concentration.
WARNING: see hazardous precautions for media containing azide.
Azide Dextrose Broth is a selective medium for the detection of enterococci in water and sewage; its composition is in accordance with WHO specifications.
The enumeration of enterococci is carried out in tubes, according to the method of the most probable number (MPN); vary the amount of inoculum (in multiples or fractions of 1ml) depending on the type of specimen preparing at least five tubes of each dilution. As a liquid dilution, use a phosphate buffer or else a 0.5% aqueous peptone solution (w/v). Incubate at 35°C for 24 hours, and observe if growth has occurred; if not, continue incubation for a further 24 hours. Calculate the result using the appropriate tables, and express it as the most probable presumptive number. Confirm the presumptive result with a subculture in Ethyl Violet Azide Broth.
User quality assurance (37°C-24 h)
E.faecalis ATCC 19433: good growth
E.coli ATCC 25922: inhibited
Dehydrated media: 15-30°C
User prepared tubes: 1 month at 2-8°C