Pathogen Gene Expression during Intestinal Infection

This chapter discusses what is known about bacterial gene expression during infection of the intestinal tract in animal models of disease. Despite the publication of numerous studies investigating gene expression by pathogens that colonize the intestinal tract, many of these studies were performed in vitro or in cell culture models of infection. While the importance of these investigations cannot be disputed, these systems do not fully represent the complex milieu of the intestinal tract, on which the chapter is focused. In addition, since many intestinal pathogens have the ability to cause serious systemic disease, bacterial gene expression has been examined at sites of systemic infection. DNA microarrays have been recently used to examine Vibrio cholerae gene expression in rabbit ligated ileal loops. Genes encoding transcriptional regulatory factors, including phoP, were absent from the set of Salmonella enterica serovar Typhimurium ivi genes induced specifically in the small intestine. Of the three Yersinia species that infect humans, Y. enterocolitica and Y. pseudotuberculosis are enteric pathogens. Yersinia enterocolitica harbors a virulence plasmid, known as pYV, that carries many genes required for virulence. Using a strain lacking this plasmid, Y. enterocolitica chromosomal intestinal ivi genes were identified in the PP of mice 24 h after oral infection. The examination of gene expression in diverse bacterial pathogens during intestinal infection has revealed much about the conditions experienced during this process.