E. coli is the major aerobic commensal organism in the gut and only causes disease following some disruption of gut, e.g. after penetrating injury. However, a number of E. coli strains or pathotypes possessing particular sets of virulence factors are adapted to cause disease in different sites, e.g. uropathogenic E. coli cause UTIs. Similarly, a number of diarrheagenic pathotypes are responsible for diarrhoeal disease.
Diarrheagenic E. coli can only be detected by molecular techniques that target the genes responsible for the production of the specific virulence factors, since culture based methods cannot distinguish diarrheagenic E. coli from commensal E. coli. Previously such molecular methods were only available in research laboratories, but the development of multiplex PCR panels targeting all key virulence genes simultaneously has allowed the detection of diarrheagenic E. coli in routine diagnostic laboratories.
A guide to diarrheagenic E.coli