h Extraintestinal Escherichia coli (ExPEC), a heterogeneous group of pathogens, encompasses avian, neonatal meningitis, and uropathogenic E. coli strains. While several virulence factors are associated with ExPEC, there is no core set of virulence factors that can be used to definitively differentiate these pathotypes. Here we describe a multiplex of four virulence factor-encoding genes, yfcV, vat, fyuA, and chuA, highly associated with uropathogenic E. coli strains that can distinguish three groups of E. coli: diarrheagenic and animal-associated E. coli strains, human commensal and avian pathogenic E. coli strains, and uropathogenic and neonatal meningitis E. coli strains. Furthermore, human intestinal isolates that encode all four predictor genes express them during exponential growth in human urine and colonize the bladder in the mouse model of ascending urinary tract infection in higher numbers than human commensal strains that do not encode the four predictor genes (P ‫؍‬ 0.02), suggesting that the presence of the predictors correlates with uropathogenic potential. Extraintestinal pathogenic Escherichia coli (ExPEC), a heterogeneous group of E. coli pathotypes defined by isolation from infections outside the intestinal tract, includes uropathogenic E. coli (UPEC), avian-pathogenic E. coli (APEC), and neonatal meningitis E. coli (NMEC) (20,32). ExPEC strains are a diverse group of pathogenic E. coli strains that cause disease in poultry and companion animals as well as humans (32). While many virulence factors are associated with ExPEC, no core set of virulence factors can unambiguously distinguish the ExPEC subgroups from one another. Therefore, strains can be designated UPEC, APEC, or NMEC only on the basis of the isolation source (20). Unlike diarrheagenic E. coli (DEC) strains, which are obligate intestinal pathogens, ExPEC strains can commensally colonize the human intestine; thus, the intestinal tract can serve as a reservoir for extraintestinal E. coli (20).This ExPEC reservoir is of particular importance for women with recurrent urinary tract infections (UTIs), as UPEC is the predominant cause of uncomplicated UTIs. It is estimated that over 50% of women will have a UTI in their lifetime; 25% will then experience a second UTI and 3% will have a third UTI within 6 months of the initial infection (5). One explanation for recurrence is that such a reservoir of UPEC in the gastrointestinal tract of this population of women is reintroduced to the urinary tract, allowing subsequent infections to occur. Indeed, UPEC clones persist long term as commensals within the intestinal tract and can even be shared among family members and household pets (13,24). A diagnostic test that could identify potential carriers of UPEC, therefore, would be beneficial for medical practitioners to determine a course for prevention of recurrent UTI. Identification of reservoirs of uropathogens could be used to identify at-risk populations and reduce disease transmission. Once carriers of UPEC are identified, the patients can be t...

Escherichia coli, a cause of ϳ90% of urinary tract infections (UTI), utilizes fimbrial adhesins to colonize the uroepithelium. Pyelonephritis isolate E. coli CFT073 carries 12 fimbrial operons, 5 of which have never been studied. Using multiplex PCR, the prevalence of these 12 and 3 additional fimbrial types was determined for a collection of 303 E. coli isolates (57 human commensal, 32 animal commensal, 54 asymptomatic bacteriuria, 45 complicated UTI, 38 uncomplicated cystitis, and 77 pyelonephritis). The number of fimbrial types per E. coli isolate was distributed bimodally: those with low (3.2 ؎ 1.1) and those with high (8.3 ؎ 1.3) numbers of fimbrial types (means ؎ standard errors of the means). The fimbrial genes ygiL, yadN, yfcV, and c2395 were significantly more prevalent among urine isolates than human commensal isolates. The effect of deletion of Ygi and Yad fimbrial operons on growth, motility, biofilm formation, adherence to immortalized human epithelial cells, and pathogenesis in the mouse model of UTI was examined. Yad fimbriae were necessary for wild-type levels of adherence to a bladder epithelial cell line and for biofilm formation. Deletion of these fimbrial genes increased motility. Ygi fimbriae were necessary for wild-type levels of adherence to a human embryonic kidney cell line, biofilm formation, and in vivo fitness in the urine and kidneys. Complementation of each fimbrial mutant restored wild-type levels of motility, biofilm formation, adherence and, for ygi, in vivo fitness. A double deletion strain, ⌬ygi ⌬yad, was attenuated in the urine, bladder, and kidneys in the mouse model, demonstrating that these fimbriae contribute to uropathogenesis.Uropathogenic Escherichia coli (UPEC) is the most prevalent cause of uncomplicated urinary tract infection (UTI) and one of the most common human pathogens (7). To better combat this pathogen, through the development of vaccines or alternative therapeutic approaches, it is imperative to understand the factors required for UPEC to successfully colonize its host. Numerous virulence factors have been determined, including toxins, siderophores, capsule, and adhesins (21-24, 36); however, no core set of virulence factors has been identified that defines all UPEC isolates.The first recognized virulence factors of UPEC were two fimbrial adhesins, type 1 and P fimbriae (19). Indeed, E. coli encodes both the chaperone-usher fimbriae and type IV pili (53). Chaperone-usher fimbriae are rigid rod-like structures with flexible fibrillar tips that terminate in an adhesin (17, 48). These fimbriae are comprised of main subunits, accessory pilins, and adhesins that are transported to the periplasm through the Sec system. Periplasmic chaperones bind the subunits and ensure proper folding as well as transport the subunits to the outer membrane usher (17, 48). In the outer membrane, a dimer of usher proteins docks each subunit and adds it to a growing fimbria (17).Chaperone-usher fimbriae are subdivided into clades based on the sequence of the usher proteins, with type...

Virulence assessment of 67 E. coli urosepsis isolates in a murine sepsis model in relation to host and bacterial characteristics suggested that host compromise, including older age and urinary tract abnormalities, allows comparatively low-virulence E. coli strains to cause urosepsis.

Uropathogenic Escherichia coli (UPEC) is a leading etiological agent of bacteremia in humans. Virulence mechanisms of UPEC in the context of urinary tract infections have been subjected to extensive research. However, understanding of the fitness mechanisms used by UPEC during bacteremia and systemic infection is limited. A forward genetic screen was utilized to detect transposon insertion mutants with fitness defects during colonization of mouse spleens. An inoculum comprised of 360,000 transposon mutants in the UPEC strain CFT073, cultured from the blood of a patient with pyelonephritis, was used to inoculate mice intravenously. Transposon insertion sites in the inoculum (input) and bacteria colonizing the spleen (output) were identified using high-throughput sequencing of transposon-chromosome junctions. Using frequencies of representation of each insertion mutant in the input and output samples, 242 candidate fitness genes were identified. Co-infection experiments with each of 11 defined mutants and the wild-type strain demonstrated that 82% (9 of 11) of the tested candidate fitness genes were required for optimal fitness in a mouse model of systemic infection. Genes involved in biosynthesis of poly-N-acetyl glucosamine (pgaABCD), major and minor pilin of a type IV pilus (c2394 and c2395), oligopeptide uptake periplasmic-binding protein (oppA), sensitive to antimicrobial peptides (sapABCDF), putative outer membrane receptor (yddB), zinc metallopeptidase (pqqL), a shikimate pathway gene (c1220) and autotransporter serine proteases (pic and vat) were further characterized. Here, we report the first genome-wide identification of genes that contribute to fitness in UPEC during systemic infection in a mammalian host. These fitness factors may represent targets for developing novel therapeutics against UPEC.