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ENDO AGAR BASE
Code: CM0479
A modified medium requiring the addition of basic fuchsin to form Endo Agar.
Typical Formula* | gm/litre |
Peptone | 10.0 |
Lactose | 10.0 |
Di-potassium phosphate | 3.5 |
Sodium sulphite | 2.5 |
Agar | 10.0 |
pH 7.5 ± 0.2 @ 25°C |
* Adjusted as required to meet performance standards
DirectionsSuspend 36g in 1 litre of distilled water. Add 4ml (or as directed by the supplier) of a 10% w/v alcoholic solution of basic fuchsin BR0050 (50:50 ethanol/distilled water). Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes. Mix well before pouring. Plates should be stored in the dark to preserve their pale pink colour.
BASIC FUCHSIN IS A POTENTIAL CARCINOGEN AND CARE SHOULD BE TAKEN TO AVOID INHALATION OF THE POWDERED DYE AND CONTAMINATION OF THE SKIN.
DescriptionEndo Agar is a long established medium which was originally devised for the isolation of the typhoid bacillus. More reliable media for this purpose have since been evolved, and the medium is now used for the differentiation of lactose fermenting and non-lactose fermenting intestinal organisms, particularly during confirmation of the presumptive test for coliforms. Production of both acid and aldehyde by lactose fermenting organisms, such as Escherichia coli, gives rise to the characteristic red coloration of the colony and the surrounding medium.
TechniqueFor the confirmation of presumptive tests with liquid media, subculture tubes showing gas, or acid and gas formation, onto an Endo Agar plate. Incubate for 24 hours at 35°C.
Lactose fermenting coliforms (e.g. Escherichia coli) give rise to deep red colonies which colour the surrounding medium and possess a golden metallic sheen.
Non-lactose fermenters form colourless translucent colonies, against the pink to colourless medium.
Storage conditions and Shelf lifeStore the dehydrated medium at 10-30°C and use before the expiry date on the label.Store the prepared plates at 2-8°C away from light.
AppearanceDehydrated medium: Straw coloured, free-flowing powderPrepared medium: Straw coloured gel
Quality control
Positive controls: | Expected results |
| Escherichia coli ATCC® 25922 * | Good growth; red colonies, red medium, golden sheen |
Enterobacter aerogenes ATCC® 13048 * | Good growth; pink / red coloured colonies no sheen |
Negative control: | |
| Staphylococcus aureus ATCC® 25923 * | Inhibited |
