Endo agar

Endo agar (also called Endo's medium) is a microbiological growth medium with a faint pink colour.^[1] Originally developed for the isolation of Salmonella typhi, it is now used mostly as a coliform medium. Most gram-negative organisms grow well in this medium, while growth of gram-positive organisms is inhibited.^[2] Coliform organisms ferment the lactose in this medium, producing a green metallic sheen (i.e. Escherichia coli), whereas non-lactose-fermenting organisms produce clear, colourless colonies,^[1] i.e. Salmonella species.

Endo agar

Typical composition

Endo agar typically contains (w/v):^[3]

• 1.0 % peptone
• 0.25 % dipotassium hydrogen phosphate (K₂HPO₄)
• 1.0 % lactose
• 0.33 % anhydrous sodium sulfite (Na₂SO₃)
• 0.03 % fuchsine
• 1.25 % agar