The Yersiniabactin-Associated ATP Binding Cassette Proteins YbtP and YbtQ Enhance Escherichia coli Fitness during High-Titer Cystitis

Abstract

The Yersinia high-pathogenicity island (HPI) is common to multiple virulence strategies used by Escherichia coli strains associated with urinary tract infection (UTI). Among the genes in this island are ybtP and ybtQ, encoding distinctive ATP binding cassette (ABC) proteins associated with iron(III)-yersiniabactin import in Yersinia pestis. In this study, we compared the impact of ybtPQ on a model E. coli cystitis strain during in vitro culture and experimental murine infections. A ybtPQ-null mutant exhibited no growth defect under standard culture conditions, consistent with nonessentiality in this background. A growth defect phenotype was observed and genetically complemented in vitro during iron(III)-yersiniabactin-dependent growth. Following inoculation into the bladders of C3H/HEN and C3H/HeOuJ mice, this strain exhibited a profound, 10 6 -fold competitive infection defect in the subgroup of mice that progressed to high-titer bladder infections. These results identify a virulence role for YbtPQ in the highly inflammatory microenvironment characteristic of high-titer cystitis. The profound competitive defect may relate to the apparent selection of Yersinia HPI-positive E. coli in uncomplicated clinical UTIs. Urinary tract infection (UTI) is one of the most common bacterial infections, affecting nearly 9 million individuals every year in the United States (1). Uropathogenic Escherichia coli (UPEC) is responsible for over 80% of all community-acquired UTI cases and in some patients progresses from a localized bladder infection to an infection of the kidneys and bloodstream (2, 3). Over 50% of women acquire a UTI over their lifetimes, with 30% suffering from recurrent UTIs (4, 5). Uncomplicated UTIs appear to follow an ascending route of infection in which the bladder is exposed to a polymicrobial inoculum of intestinal bacteria that colonize the vaginal vestibule and urethra (6-10). This early colonization event may precede patients' visits to physicians by several days. Our understanding of the molecular mechanisms that UPEC uses to emerge from this early inoculum and dominate the urinary microbiome at the time of clinical UTI diagnosis remains incomplete.When an uncomplicated UTI patient's rectal and urinary E. coli strains are compared, the urinary strain is more likely to carry the 30-kb Yersinia high-pathogenicity island (HPI) (11). The Yersinia HPI is nearly ubiquitous among model uropathogenic E. coli strains, is associated with fluoroquinolone resistance when present in combination with the aerobactin siderophore system, and is typically present in over 70% of clinical urinary isolates (3,11,12). The Yersinia HPI encodes the yersiniabactin (Ybt) siderophore system, including yersiniabactin biosynthetic enzymes, in addition to outer and inner membrane transporters associated with metal-yersiniabactin complex import (13-16). Yersiniabactin is one of three genetically nonconserved E. coli siderophore types (yersiniabactin, salmochelin, and aerobactin) that may be expressed in addition to enterobactin, the...

Enterobacteria secrete an inhibitor of Pseudomonas virulence during clinical bacteriuria

“…coli siderophore-dependent growth assay. The assay was adapted from a previously published Fe(III)-Ybt-dependent growth assay, and apo-Ybt was purified as previously described (16,19). UTI89 was grown overnight in LB broth at 37°C under shaking conditions and then washed 3 times by centrifugation and resuspension in a volume of PBS equal to the culture volume.…”

“…These results suggest that the early stages of ascending UTI are competitive and favor isolates with specific siderophore profiles. In this and other studies, Ybt, a siderophore encoded by the Yersinia high pathogenicity island (HPI), was associated with urinary tract virulence (7,(13)(14)(15)(16)(17).…”

Pathogenic siderophore ABC importer YbtPQ adopts a surprising fold of exporter

“…Thus, the import of metal-chelated Ybt is an essential pathway for the microbes to acquire necessary metal ions. It has been established that deletion of YbtP or YbtQ gene in UPEC has no effect on the extracellular release of metal-free Ybt, but has detrimental effect on the intracellular metal uptake and later leads to profound decreased UTIs in a cystitis mouse model (11). Thus, it is suggested that the heterodimer YbtPQ is an ABC importer responsible for specific uptake of metal-chelated Ybt molecules.…”

Copper import in Escherichia coli by the yersiniabactin metallophore system

“…Among HPI-encoded proteins, transport-associated outer and inner membrane proteins are required for Fe(III)-Ybt dependent growth and are expressed in a YbtA-dependent manner 8 , 9 , 12 , 13 . FyuA ( f erric y ersiniabactin u ptake A, Psn in Yersinia pestis ) is an outer membrane protein with structural and functional features that are typical of TonB-dependent outer membrane siderophore transporters 13 , 14 .…”