Phenol red broth base 500g

Description

Test culture medium used, together with various reactants, for the biochemical identification of microorganisms by means of fermentation tests.

Mode of Action
Fermentation of the added reactant by the inoculated culture causes phenol red to change its colour from red to yellow. When testing anaerobes, addition of a small quantity of agar stabilizes the anaerobiosis.

Typical Composition (g/litre)
Peptone from casein 5.0; peptone from meat 5.0; sodium
chloride 5.0; phenol red 0.018.
Also to be added (g/litre):
reactant 5.0-10.0; if required, agar-agar 0.5-1.0.

Preparation
Suspend 15 g/litre, if requested, together with 0.5-1.0 g agaragar/litre, dispense into test tubes, if necessary insert DURHAM tubes, autoclave (15 min at 121 °C). After cooling to about 60 °C add the desired reactants (final concentration 5.0-10.0 g/litre) as filter-sterilized solutions.
pH: 7.4 ± 0.2 at 25 °C.
The prepared broth is clear and red.

Experimental Procedure and Evaluation
Inoculate the tubes dropwise with pure cultures of the microorganisms to be identified. Tubes without reactant should also be inoculated to serve as growth controls. In case of particularly fastidious microorganisms, it is advised to add a few drops of sterile, inactivated serum to each tube.
Anaerobes should be tested under anaerobic conditions in a culture medium containing agar.
Incubation: up to 14 days at the optimal incubation temperature (usually 35 °C), in general 24 hours aerobically.
Check the tubes daily during incubation for gas formation in the DURHAM tubes and to see whether the colour has changed from red to yellow. If the phenol red is degraded, it may be freshly added dropwise as 5 % solution, when checking the tubes