Members of the genera
Escherichia
and
Shigella
are most often associated with infections of the gastrointestinal and urinary tracts, but may also cause more severe systemic or invasive infections including pneumonia, sepsis, and meningitis. This chapter provides an overview of each genus and discusses key aspects of taxonomy, epidemiology, and virulence, along with culture‐dependent and culture‐independent methodologies for the identification and classification of species within these genera. It discusses recent trends in antimicrobial resistance patterns and updates to recommended susceptibility testing modalities and interpretive criteria to understand the current best practice for treating active infections. The epidemiology and clinical impact of EIEC are difficult to ascertain because of its close relationship to
Shigella
and the difficulty in distinguishing EIEC from
Shigella
by using biochemical, phenotypic, and molecular methods. Appropriate transport of fecal specimens is essential for effective culture‐based recovery of bacterial pathogens associated with gastroenteritis.