Endo Agar is a differential and slightly selective culture medium for the detection of coliform and other enteric microorganisms.

The majority of the enteric plating media developed in the early years of the 20th century utilized either mixtures of bile salts or individual salts as selective agents to achieve inhibition of gram-positive species. In 1904, Endo reported the development of a culture medium for the differentiation of lactose fermenters from the nonfermenters in which no bile salts were used.¹ Inhibition of gram-positive microorganisms was achieved by the sodium sulfite and basic fuchsin contained in the formulation. Endo's Fuchsin Sulphite Infusion Agar was the original name for this medium² which is known today as Endo Agar. It was initially developed in order to facilitate the isolation and identification of the typhoid bacillus.

The original formula has been modified extensively since its introduction. The meat infusions have been replaced by a peptic digest of animal tissue. The dye composition and concentration also have been adjusted.

Over the years, Endo Agar has been an important medium in the microbiological examination of potable water and wastewater, dairy products and foods; however, the current compendia of standard methods for the examination of these materials recommend alternative media formulations.^3-5