The Genus Escherichia

Escherichia coli, originally called “Bacterium coli commune,” was first isolated from the feces of a child in 1885 by the Austrian pediatrician Theodor Escherich (Escherich, 1885). Escherichia coli is a common inhabitant of the gastrointestinal tract of humans and animals. There are E. coli strains that are harmless commensals of the intestinal tract and others that are major pathogens of humans and animals. The pathogenic E. coli are divided into those strains causing disease inside the intestinal tract and others capable of infection at extra-intestinal sites (Kaper et al., 2004). Escherichia coli is easily cultured in the clinical laboratory, but the identification of the different pathogenic genotypes requires virulence gene detection methods not typically available in most clinical laboratories. Escherichia coli can be found secondarily in soil and water as the result of fecal contamination. Classically, its detection has been used as an indicator of poor water quality. From biochemical, physiological and genetic perspectives, E. coli is one of the best understood and characterized living organisms, with laboratory studies on model strains such as E. coli K-12 taking place over the past sixty years (extensively reviewed in Escherichia coli and Salmonella: Cellular and Molecular Biology, third edition; available online through the http://www.asmpress.org/browse/virtual/index. asp?SelectedItem=10075{ASM Press Web site}). Shown in Table 1 are additional websites providing general and specific E. coli portals for useful genetic and metabolic information.