Role of Capsule and O Antigen in the Virulence of Uropathogenic Escherichia coli

Sarkar, Sohinee; Ulett, Glen C.; Totsika, Makrina; Phan, Minh-Duy; Schembri, Mark A.

doi:10.1371/journal.pone.0094786

Cited by 108 publications

(87 citation statements)

References 97 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…First, we determined the serum susceptibility of E. coli strain CFT073. Our results show that CFT073 is not strictly serum resistant as previously reported (6,8,9,31,32). Rather, only a fraction of cells survived serum treatment (Fig.…”

Section: Discussionsupporting

confidence: 77%

“…The CFT073 strain was isolated from the blood of a patient with acute pyelonephritis, so it is representative of UPEC strains that can cause bacteremia (25). CFT073 has been reported to be serum resistant (6,8,9,31,32). However, the experimental conditions for defining serum resistance are not standardized; the growth phase of the harvested bacteria, bacterial cell density, serum concentration, and incubation time can influence the number of cells that survive in the presence of serum (11)(12)(13)(14)33).…”

Section: Subpopulation Of Cft073 Cells Is Tolerant To Human Serummentioning

confidence: 99%

“…In addition, secretion of the exopolysaccharide colanic acid protects UPEC from complement-mediated killing (8). Modification of lipopolysaccharide (LPS) is also important for complement evasion (9,10). It has been shown that serum sensitivity depends on the bacterial growth phase; cells are more readily killed by serum during early logarithmic phase (11)(12)(13)(14).…”

mentioning

confidence: 99%

See 2 more Smart Citations

Phenotypic Heterogeneity Enables Uropathogenic Escherichia coli To Evade Killing by Antibiotics and Serum Complement

et al. 2015

View full text Add to dashboard Cite

Uropathogenic strains of Escherichia coli (UPEC) are the major cause of bacteremic urinary tract infections. Survival in the bloodstream is associated with different mechanisms that help to resist serum complement-mediated killing. While the phenotypic heterogeneity of bacteria has been shown to influence antibiotic tolerance, the possibility that it makes cells refractory to killing by the immune system has not been experimentally tested. In the present study we sought to determine whether the heterogeneity of bacterial cultures is relevant to bacterial targeting by the serum complement system. We monitored cell divisions in the UPEC strain CFT073 with fluorescent reporter protein. T he immune system has several pathways for recognizing and killing pathogenic bacteria. However, some pathogenic bacteria can maintain infection in mammalian hosts despite inflammation, specific antimicrobial mechanisms, and a robust adaptive immune response and can therefore give rise to persistent infection (1). Uropathogenic Escherichia coli (UPEC) causes recurrent urinary tract infections that can progress from the lower to the upper urinary tract and can lead to the dissemination of bacteria into the bloodstream.The complement system is part of the defense against invading pathogens, with an essential role in both innate and adaptive immunity (2). It is composed of more than 40 plasma and membrane proteins. It can be activated via three distinct routes: the classical (antibody dependent), lectin, and alternative pathways. Activation of complement cascades leads to the formation of the key component C3b on the bacterial surface, which stimulates phagocytosis. Late complement components (C5 to C9 proteins) are also activated via C3b, resulting in the formation of the membrane attack complex (MAC) causing cell lysis (2). The primary source of complement is blood, but complement proteins are also synthesized by a variety of other cell types and tissues (3).Bacterial resistance to serum complement killing depends on the presence or absence of antigenic outer membrane proteins (4). Pathogens often resist recognition and subsequent complement activation owing to their surface capsular polysaccharide, which masks underlying structures and by itself activates complement poorly (5-7). In addition, secretion of the exopolysaccharide colanic acid protects UPEC from complement-mediated killing (8). Modification of lipopolysaccharide (LPS) is also important for complement evasion (9, 10). It has been shown that serum sensitivity depends on the bacterial growth phase; cells are more readily killed by serum during early logarithmic phase (11)(12)(13)(14). However, there are examples showing that exponential-phase cells are more resistant to complement-mediated killing than stationary-phase cells (15,16). That phenomenon is largely explained by the growth-phase-dependent expression of antigens, capsule, and LPS modification (14, 15). Cell size can also be an important determinant of complement-mediated killing, since larger or aggregated cells ...

show abstract

Section: Discussionsupporting

confidence: 77%

Section: Subpopulation Of Cft073 Cells Is Tolerant To Human Serummentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Phenotypic Heterogeneity Enables Uropathogenic Escherichia coli To Evade Killing by Antibiotics and Serum Complement

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Uropathogenic Escherichia coli (UPEC) strains are the primary etiological agent of UTIs and cause 70 to 90% of all such infections (2). UPEC can survive in the urinary tract and cause disease due to a diverse range of virulence factors, including fimbriae (3-6), autotransporter (AT) proteins (7)(8)(9)(10), surface polysaccharides, such as the O antigen and capsule (11)(12)(13), iron acquisition systems (14)(15)(16), and toxins (17)(18)(19)(20)(21).…”

mentioning

confidence: 99%

Molecular Characterization of the Vacuolating Autotransporter Toxin in Uropathogenic Escherichia coli

et al. 2016

Self Cite

View full text Add to dashboard Cite

The vacuolating autotransporter toxin (Vat) contributes to uropathogenic Escherichia coli (UPEC) fitness during systemic infection. Here, we characterized Vat and investigated its regulation in UPEC. We assessed the prevalence of vat in a collection of 45 UPEC urosepsis strains and showed that it was present in 31 (68%) of the isolates. The isolates containing the vat gene corresponded to three major E. coli sequence types (ST12, ST73, and ST95), and these strains secreted the Vat protein. Further analysis of the vat genomic locus identified a conserved gene located directly downstream of vat that encodes a putative MarR-like transcriptional regulator; we termed this gene vatX. The vat-vatX genes were present in the UPEC reference strain CFT073, and reverse transcriptase PCR (RT-PCR) revealed that the two genes are cotranscribed. Overexpression of vatX in CFT073 led to a 3-fold increase in vat gene transcription. The vat promoter region contained three putative nucleation sites for the global transcriptional regulator histone-like nucleoid structuring protein (H-NS); thus, the hns gene was mutated in CFT073 (to generate CFT073 hns). Western blot analysis using a Vat-specific antibody revealed a significant increase in Vat expression in CFT073 hns compared to that in wild-type CFT073. Direct H-NS binding to the vat promoter region was demonstrated using purified H-NS in combination with electrophoresis mobility shift assays. Finally, Vat-specific antibodies were detected in plasma samples from urosepsis patients infected by vat-containing UPEC strains, demonstrating that Vat is expressed during infection. Overall, this study has demonstrated that Vat is a highly prevalent and tightly regulated immunogenic serine protease autotransporter protein of Enterobacteriaceae (SPATE) secreted by UPEC during infection. IMPORTANCEUropathogenic Escherichia coli (UPEC) is the major cause of hospital-and community-acquired urinary tract infections. The vacuolating autotransporter toxin (Vat) is a cytotoxin known to contribute to UPEC fitness during murine sepsis infection. In this study, Vat was found to be highly conserved and prevalent among a collection of urosepsis clinical isolates and was expressed at human core body temperature. Regulation of vat was demonstrated to be directly repressed by the global transcriptional regulator H-NS and upregulated by the downstream gene vatX (encoding a new MarR-type transcriptional regulator). Additionally, increased Vat-specific IgG titers were detected in plasma from corresponding urosepsis patients infected with vatpositive isolates. Hence, Vat is a highly conserved and tightly regulated urosepsis-associated virulence factor. U rinary tract infections (UTIs) are one of the most common human infections, affecting 40 to 50% of women and approximately 12% of men globally (1). UTIs are ascending infections and can involve infection of the bladder (cystitis), kidneys (pyelonephritis), or dissemination into the bloodstream (urosepsis). Uropathogenic Escherichia coli (UPEC) strains ...

show abstract

“…DegP and DegQ contain a central protease domain flanked by two PDZ domains (PDZ1 and PDZ2) (Sassoon et al, 1999, Krojer et al, 2002. DegP exists as an inactive hexameric protein ( Figure 1.7), consisting of two face-to-face trimer complexes (Krojer et al, 2002, Jomaa et al, 2007.…”

Section: Serine Protease Chaperonesmentioning

confidence: 99%

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

Nichols¹

View full text Add to dashboard Cite

Uropathogenic Escherichia coli (UPEC) are the primary cause for all urinary tract infections.Autotransporter (AT) proteins are virulence factors secreted by the type V secretion pathway. This project examined the prevalence, regulation and expression of the vacuolating AT toxin (Vat), and the role of periplasmic chaperone proteins in AT translocation.The vacuolating autotransporter (AT) toxin (Vat) contributes to Uropathogenic Escherichia coli (UPEC) fitness during systemic infection. Vat is a serine protease AT of Enterobacteriaceae (SPATE) with cytotoxic activity. Here we characterised Vat and investigated its regulation in UPEC.We assessed the prevalence of vat in a collection of 45 UPEC urosepsis strains and showed it that was present in 31 (68%) of the isolates. The isolates containing the vat gene corresponded to three major E. coli sequence types (ST12, 73 and 95) and these strains secreted the Vat protein.Further analysis of the vat genetic locus identified a conserved gene located directly downstream of vat that encodes a putative MarR-like transcriptional regulator, which we termed vatX. The vatvatX genes were present in the UPEC reference strain CFT073 and RT-PCR revealed both genes are co-transcribed. Over-expression of vatX in CFT073 led to a 3-fold increase in vat gene transcription. The vat promoter region contained three putative nucleation sites for the global transcriptional regulator H-NS; thus the hns gene was mutated in CFT073 (to generate CFT073hns).Western blot analysis using a Vat-specific antibody revealed a significant increase in Vat expression in CFT073hns compared to wild-type CFT073. Direct H-NS binding to the vat promoter region was demonstrated using purified H-NS in combination with electrophoresis mobility shift assays. Finally, Vat-specific antibodies were detected in plasma samples from urosepsis patients iv Declaration by authorThis thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis.

show abstract

Role of Capsule and O Antigen in the Virulence of Uropathogenic Escherichia coli

Cited by 108 publications

References 97 publications

Phenotypic Heterogeneity Enables Uropathogenic Escherichia coli To Evade Killing by Antibiotics and Serum Complement

Phenotypic Heterogeneity Enables Uropathogenic Escherichia coli To Evade Killing by Antibiotics and Serum Complement

Molecular Characterization of the Vacuolating Autotransporter Toxin in Uropathogenic Escherichia coli

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

Contact Info

Product

Resources

About