Principles and uses
Endo Agar Base is a differential and moderately selective culture medium for the detection and confirmation of coliforms and other enteric microorganisms in waters, milk, dairy and other food products.
It uses fuchsin to differentiate between positive lactose-fermenting and lactose non-fermenting bacteria. Acetaldehyde production by lactose-fermenting organisms such as E. coli produce characteristic red colonies and a red surrounding area, marked by its reaction with Sodium sulphite in the presence of fuchsin. Lactose non-fermenters form colorless, transparent colonies.
Peptone provides nitrogen, vitamins, minerals and amino acids essential for growth. Lactose is the fermentable carbohydrate providing carbon and energy. Dipotassium phosphate acts as a buffer system. Bacteriological agar is the solidifying agent.

Formula:

For 1 liter of media :
– Pancreatic digest of meat……………………………………………………………………………… 10,0 g
– Lactose………………………………………………………………………………………………………. 10,0 g
– Dipotassium phosphate………………………………………………………………………………….. 3,5 g
– Sodium sulfite……………………………………………………………………………………………….. 2,5 g
– Basic fuchsin ……………………………………………………………………………………………….. 0,5 g
– Bacteriological agar……………………………………………………………………………………… 15,0 g
pH of the ready-to-use media at 25 °C : 7,5 ± 0,2. 

Preparation
Dissolve 41,5 g of dehydrated media (BK057) in 1 liter of distilled or demineralized water.
 Slowly bring to boiling, stirring with constant agitation until complete dissolution.
 Dispense in tubes or flasks.
 Sterilize in an autoclave at 121 °C for 15 minutes.
 Cool and maintain in a molten state at 44-47 °C.
 Mix well in order to distribute any precipitate.
 Pour into sterile Petri plates and let solidify on a cool, even surface.
 Dry the plates in an incubator, covers partially removed.