Originally: any of various bacilli that inhabit the intestines of animals. In later use: any bacterium of the family Enterobacteriaceae, the members of which are straight Gram-negative rods which are found in water, soil, decaying organic material, and plants as well as in the intestines of animals, and include important pathogens of both animals and plants.
The human pathogens of this family cause a variety of diseases including diarrhoeal illness, typhoid and paratyphoid fevers, and opportunistic infections; they include Salmonella and Shigella species, certain strains of Escherichia coli, and various others.
1920s. From entero- + bacterium.