Pathogenic Escherichia coli, Shigella, and Salmonella

Abstract

The gram-negative enteric pathogens are a closely related group of bacteria. On the basis of genome analyses, Escherichia coli and Shigella can be considered a single species, and their classification as separate genera is largely historical. The Salmonella species are evolutionarily more distant but share many characteristics with the E. coli group. The enteric pathogens usually initiate infection following ingestion, causing diseases ranging from relatively mild enteritis to dysentery and septicemia. The extent of invasion and the nature of the disease depend on the specific set of virulence factors expressed by these pathogens. This chapter discusses the pathogenic members of the enteric bacteria. Many of the iron transport systems originally described in E. coli K-12 are found also in the enteric pathogens. The chapter first talks about siderophore-mediated iron transport systems and nonsiderophore iron transport systems. Next, it summarizes the current state of knowledge with respect to the role of iron transport systems in the pathogenesis of Salmonella, Shigella, and E. coli. Pathogenic E. coli strains are associated with a variety of different diseases and cause both intestinal and extraintestinal infections. While the precise roles of each iron transport system in transmission, colonization, survival, and spread of enteric pathogens in the host cannot be unambiguously defined, several features of iron transport in the enteric pathogens are clear.