Walsh & Hoyt: Enterobacteriaceae

A large, heterogeneous group of gram-negative bacilli make up the family Enterobacteriaceae. These bacteria include a number of genera whose species are major human intestinal pathogens (e.g., Salmonella, Shigella, Yersinia), and several that are normal colonizers of the human gastrointestinal tract (e.g., Enterobacter, Escherichia, Klebsiella). Because of this colonization tropism, a number of member strains are also called ""enteric bacteria,"" a designation that includes other gram-negative bacilli not in the Enterobacteriaceae family but that are also found in the normal human gastrointestinal tract, such as Pseudomonas species. The terms ""Enterobacteriaceae"" and ""enteric bacteria"" thus refer to overlapping rather than identical sets of organisms.