The repeat-in-toxin (RTX) family member TosA mediates adherence of Uropathogenic Escherichia coli to urinary tract epithelial cells and enhances survival and toxicity during bacteremia and sepsis

Uropathogenic Escherichia coli (UPEC) are responsible for the majority of uncomplicated urinary tract infections (UTI) and represent the most common bacterial infection of the adult population. UPEC utilize a wide range of virulence factors to colonize the host environment, including the secreted protein toxin α-hemolysin. While a great deal is known about this protein, which serves as the prototype of a large family of secreted bacterial proteins termed the repeats-in-toxin (RTX) family, the protein itself has only a minor contribution to UPEC pathogenesis. The work contained in this dissertation describes a novel RTX family member, TosA, which was discovered in a screen of proteins synthesized by a human UPEC strain that were recognized as antigenic during chronic UTI in an animal model of infection. TosA was determined to be specifically expressed in the host urinary tract and contributed significantly to the virulence and survival of UPEC. TosA was only found in the B2 phylogenetic subgroup of E. coli and served as a marker for a group of isolates that also contained a large number of well characterized UPEC virulence factors. The presence of the gene tosA was determined to predict the success of fecal isolates in the murine model of ascending UTI regardless of the source of the isolate. Finally, a detailed analysis of the function of tosA revealed that this gene is linked to genes encoding a conserved type 1 secretion system similar to other RTX family members and may be part of large regulatory network that includes other UPEC adherence factors. The TosA protein was found to mediate i) adherence to host cells derived from the upper urinary tract, ii) survival in disseminated infections, and iii) enhanced lethality during sepsis (as discovered in two different animal models of infection). An experimental vaccine using purified protein protected vaccinated animals against urosepsis. From this work, it was concluded that TosA belongs to a novel group of RTX proteins that mediate adherence and host damage during UTI and urosepsis, and may be a novel target for the development of new therapeutics to treat ascending urinary tract infections.