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Bacterial pathogenicity islands (PAI) often encode both effector molecules responsible for disease and secretion systems that deliver these effectors to host cells. Human enterohemorrhagic Escherichia coil (EHEC), enteropathogenic E. coil, and the mouse pathogen Citrobacter rodentium (CR) possess the locus of enterocyte effacement (LEE) PAI. We systematically mutagenized all 41 CR LEE genes and functionally characterized these mutants in vitro and in a murine infection model. We identified 33 virulence factors, including two virulence regulators and a hierarchical switch for type III secretion. In addition, 7 potential type III effectors encoded outside the LEE were identified by using a proteomics approach. These non-LEE effectors are encoded by three uncharacterized PAIs in EHEC O157, suggesting that these PAIs act cooperatively with the LEE in pathogenesis. Our findings provide significant insights into bacterial virulence mechanisms and disease.

Author(s): Samantha Gruenheid; B. Brett Finlay (corresponding author) To induce cytoskeletal changes, pathogenic microbes must ensure delivery of effector molecules onto or into host cells. Effectors are usually proteins that [...]

The identification of three genomic islands encoding non-LEE effector (nle) genes and 14 individual nle genes in non-O157 shiga toxin-producing Escherichia coli (STEC) strains is reported. A molecular risk assessment method to rapidly recognize and respond to non-O157 STEC strains is presented.