Fimbrial Profiles Predict Virulence of Uropathogenic Escherichia coli Strains: Contribution of Ygi and Yad Fimbriae

Abstract

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...

Cloning, purification, crystallization and preliminary X-ray diffraction studies ofEscherichia coliPapD-like protein (EcpD)

“…EcpD shares $40% homology with the uropathogenic E. coli PapD protein (Raina et al, 1993); it is supposed to be involved in the proper folding of Yad fimbrial proteins and in guiding them to the outer membrane usher in a systematic manner, thereby adding to the growing fimbriae (Korea et al, 2010;Tønjum et al, 1993). Previous studies have shown that the formation of Yad fimbriae is essential for the wild-type level of adhesion to the host epithelial cell, colonization and biofilm formation of UPEC (Spurbeck et al, 2011).…”

“…Recent studies have shown the importance of yad genes in adherence, as the deletion of yad genes increases cell motility. However, less is known about the fimbriae that are mainly found in UPEC and help in adhesion and infection (Spurbeck et al, 2011). Considering the significant role of EcpD in such a highly orchestrated interplay of molecules, its structural and functional characterization is necessary in order to understand the mechanism of pilus biogenesis and its role in virulence.…”

“…Of these five classes, the chaperone-usher (CU) pili often contribute to virulence and hence it is necessary to understand the role of these pili in host-pathogen interactions (Fronzes et al, 2008). EcpD is a periplasmic chaperone of Yad CU pili which is known to play a significant role in pilus biogenesis and is prevalently found in uropathogenic Escherichia coli (UPEC), which predominantly infects bladder epithelial cells (Spurbeck et al, 2011). EcpD shares $40% homology with the uropathogenic E. coli PapD protein (Raina et al, 1993); it is supposed to be involved in the proper folding of Yad fimbrial proteins and in guiding them to the outer membrane usher in a systematic manner, thereby adding to the growing fimbriae (Korea et al, 2010;Tønjum et al, 1993).…”

What does it take to stick around?

“…8 UPEC harbor numerous CUP pili systems, the differential expression of which is thought to facilitate colonization of different niches. [9][10][11][12][13] Type 1 pili mediate adherence largely via the FimH tip adhesin, which recognizes and binds mannosylated moieties on biotic and abiotic surfaces. 4,6,[14][15][16][17][18][19][20] Within the host, FimH mediates UPEC binding to the bladder epithelium and is also required for proper formation of biofilm-like intracellular bacterial communities (IBCs) within bladder epithelial cells.…”

Autotransporter proteins of Uropathogenic Escherichia coli: regulation, characterisation and the role of periplasmic proteins in their expression

“…Type 1 and P fimbriae represent the two best studied fimbriae present in UPEC. Some of the more recently characterised UPEC fimbriae include F9, type 3-like, Ygi and Yad (Spurbeck et al, 2011, Ulett et al, 2007a, Ong et al, 2008. The genes encoding for fimbriae are always contained within a single operon (Wurpel et al, 2013), and are often phase variable (e.g.…”