Endo agar (also called Endo’s medium) is a microbiological growth medium with a faint pink colour.
Endo agar
Purpose :
Endo agar is used to detect fecal contamination in water and dairy products. Whereas its current use is to isolate and identify the presence of enteric lactose fermenters (coliforms), its original use was to isolate and identify Salmonella typhi, a lactose nonfermenter (noncoliform).
Principle:
Endo Agar contains color indicators sodium sulfite and basic fuchsin (which also double as Gram-positive inhibitors).
Lactose is included as a fermentable carbohydrate.
Lactose fermenters ( growing on the medium will appear red or pink and darken the medium slightly due to the reaction of sodium sulfite with the fermentation intermediate acetaldehyde.
Lactose nonfermenters produce colorless to slightly pink growth .
Some lactose fermenters, such as Escherichia coliand, Klebsiella pneumoniae produce large amounts of acid, which gives the colonies a metallic sheen .
Ecoli on Endo agar
