Dimeric and Trimeric Fusion Proteins Generated with Fimbrial Adhesins of Uropathogenic Escherichia coli

Specific Detection of Uropathogenic Escherichia coli via Fourier Transform Infrared Spectroscopy Using an Optical Biosensor

Urinary tract infections (UTIs) are caused mainly by uropathogenic Escherichia coli (UPEC), accounting for both uncomplicated (75%) and complicated (65%) UTIs. Detecting UPEC in a specific, rapid, and timely manner is essential for eradication, and optical biosensors may be useful tools for detecting UPEC. Recently, biosensors have been developed for the selective detection of antigen-antibody-specific interactions. In this study, a methodology based on the principle of an optical biosensor was developed to identify specific biomolecules, such as the PapG protein, which is located at the tip of P fimbriae and promotes the interaction of UPEC with the uroepithelium of the human kidney during a UTI. For biosensor construction, recombinant PapG protein was generated and polyclonal anti-PapG antibodies were obtained. The biosensor was fabricated in silicon supports because its surface and anchor biomolecules can be modified through its various properties. The fabrication process was carried out using self-assembled monolayers (SAMs) and an immobilized bioreceptor (anti-PapG) to detect the PapG protein. Each stage of biosensor development was evaluated by Fourier transform infrared (FTIR) spectroscopy. The infrared spectra showed bands corresponding to the C-H, C=O, and amide II bonds, revealing the presence of the PapG protein. Then, the spectra of the second derivative were obtained from 1600 to 1700 cm-1 to specifically determine the interactions that occur in the secondary structures between the biological recognition element (anti-PapG antibodies) and the analyte (PapG protein) complex. The analyzed secondary structure showed β-sheets and β-turns during the detection of the PapG protein. Our data suggest that the PapG protein can be detected through an optical biosensor and that the biosensor exhibited high specificity for the detection of UPEC strains. Furthermore, these studies provide initial support for the development of more specific biosensors that can be applied in the future for the detection of clinical UPEC samples associated with ITUs.

Polysaccharides from Vaccaria segetalis seeds reduce urinary tract infections by inhibiting the adhesion and invasion abilities of uropathogenic Escherichia coli

The seeds of Vaccaria segetalis (Neck.) are from a traditional medicinal plant Garcke, also called Wang-Bu-Liu-Xing in China. According to the Chinese Pharmacopoeia, the seeds of V. segetalis can be used for treating urinary system diseases. This study was designed to investigate the underlying mechanism of VSP (polysaccharides from Vaccaria segetalis) against urinary tract infections caused by uropathogenic Escherichia coli (UPEC). Here, both in vitro and in vivo infection models were established with the UPEC strain CFT073. Bacterial adhesion and invasion into bladder epithelial cells were analyzed. We found that VSP reduced the adhesion of UPEC to the host by inhibiting the expression of bacterial hair follicle adhesion genes. VSP also reduced the invasion of UPEC by regulating the uroplakins and Toll-like receptors of host epithelial cells. In addition, the swarming motility and flagella-mediated motility genes flhC, flhD and Flic of UPEC were diminished after VSP intervention. Taken together, our findings reveal a possible mechanism by which VSP interferes with the adhesion and invasion of UPEC.

Probiotics: Lactic Acid Bacteria have Antibacterial Activity and Downregulate Biofilm Genes of Uropathogenic E. coli

Urinary tract infections (UTIs) are regarded as one of the most serious infections worldwide. Uro Pathogenic E. coli (UPEC) accounts for nearly 80% of UTI infections in females. This study investigated the antibacterial and antibiofilm effects of Lactobacillus acidophilus (l. acidophilus) and Lactobacillus plantarum (lb. plantarum) on multidrug-resistant E. coli obtained from urine samples. Complete bacteriological identification was conducted on 45 E. coli isolated from 80 urine samples of females with UTIs. Antibiotic susceptibility test was performed on all isolates by nine antibiotics. Ten out of the 45 isolates exhibited multidrug resistance (MDR). L. acidophilus and Lb. plantarum showed marked inhibition of MDR E. coli isolates on agar by a diffusion method (16 ± 0.04: 23 ± 0.05 mm). Moreover, L. acidophilus and Lb. plantarum strains inhibited the ability of UPEC to form a biofilm by 56.3% and 39.63%, respectively. The expression of biofilm genes of E. coli are as follows: csgA, crl, csgD showed remarkable downregulation after treatment with probiotics suspension: 0.00364: 0.19078 fold, 0.0005: 0.1894 fold, and 0.0490: 0.0883 for L. acidophilus, respectively. On the other hand, downregulation of biofilm gene expression for csgA, crl, csgD after treatment with Lb. plantarum suspension were expressed by fold changes as follows: 0.0769: 0.3535 fold, 0.05440: 0.12940 fold, and 0.06745: 0.4146, respectively. These findings show that L. acidophilus and Lb. plantarum exhibit potent antibacterial and antibiofilm action against MDR UPEC at both genotypic and phenotypic levels, and appear to be a promising solution in therapeutic applications for recurrent and persistent UTIs.

Flagella, Type I Fimbriae and Curli of Uropathogenic Escherichia coli Promote the Release of Proinflammatory Cytokines in a Coculture System

Background. Urinary tract infections (UTIs) are a public health problem in Mexico, and uropathogenic Escherichia coli (UPEC) is one of the main etiological agents. Flagella, type I fimbriae, and curli promote the ability of these bacteria to successfully colonize its host. Aim. This study aimed to determine whether flagella-, type I fimbriae-, and curli-expressing UPEC induces the release of proinflammatory cytokines in an established coculture system. Methods. The fliC, fimH, and csgA genes by UPEC strain were disrupted by allelic replacement. Flagella, type I fimbriae, and curli were visualized by transmission electron microscopy (TEM). HTB-5 (upper chamber) and HMC-1 (lower chamber) cells cocultured in Transwell^® plates were infected with these UPEC strains and purified proteins. There was adherence to HTB-5 cells treated with different UPEC strains and they were quantified as colony-forming units (CFU)/mL. Results. High concentrations of IL-6 and IL-8 were induced by the FimH and FliC proteins; however, these cytokines were detected in low concentrations in presence of CsgA. Compared with UPEC CFT073, CFT073ΔfimH, CFT073ΔfimHΔfliC, and CFT073ΔcsgAΔfimH strains significantly reduced the adherence to HTB-5 cells. Conclusion. The FimH and FliC proteins are involved in IL-6 and IL-8 release in a coculture model of HTB-5 and HMC-1 cells.

Recombinant FimH, a fimbrial tip adhesin of Vibrio parahaemolyticus, elicits mixed T helper cell response and confers protection against Vibrio parahaemolyticus challenge in murine model

Vibrio parahaemolyticus causes vibriosis in wide range of marine organisms, and is responsible for food borne illnesses in humans through consumption of contaminated uncooked/partially cooked seafood. Continued and widespread antibiotics usage to increase the productivity has led to antibiotics resistance development. This has necessitated the need to develop alternative methods to control its infection. Use of safe and effective vaccines against the virulence factors not only protects from infection, it also minimizes antibiotic usage. The colonization of V. parahaemolyticus in the host and disease development requires several adhesins present on the cell surface, and thereby make them attractive vaccine candidates. V. parahaemolyticus produces extracellular type 1 fimbriae that have been shown to play a role in adhesion, biofilm formation and virulence. FimH is one of the minor components of the type 1 fimbriae occurring on its very tip. Being present on the cell surface, it is highly immunogenic, and can be targeted as a potential vaccine candidate. The present study describes the immunogenic and vaccine potential of recombinant V. parahaemolyticus FimH (rVpFimH) expressed in E. coli. Immunization of BALB/c mice with the rVpFimH elicited a strong mixed immune response, T-cell memory (evidenced by antibody isotyping, cytokine profiling and T-cell proliferation assay), and agglutination positive antibodies. FACS analysis and immunogold labeling showed that the polyclonal anti-rVpFimH antibodies were able to recognize the FimH on V. parahaemolyticus cells. In vivo challenge of the rVpFimH-immunized mice with 2×LD₅₀ dose of live bacteria showed one hundred percent survival. Thus, our findings clearly demonstrate the potential of FimH as an effective vaccine candidate against V. parahaemolyticus.

Interaction of microbial functional amyloids with solid surfaces

HYPOTHESIS

Self-assembling protein subunits hold great potential as biomaterials with improved functions. Among the self-assembled protein structures functional amyloids are promising unique properties such as resistance to harsh physical and chemical conditions their mechanical strength, and ease of functionalization. Curli proteins, which are functional amyloids of bacterial biofilms can be programmed as intelligent biomaterials.

EXPERIMENTS

In order to obtain controllable curli based biomaterials for biomedical applications, and to understand role of each of the curli forming monomeric proteins (namely CsgA and CsgB from Escherichia coli) we characterized their binding kinetics to gold, hydroxyapatite, and silica surfaces.

FINDINGS

We demonstrated that CsgA, CsgB, and their equimolar mixture have different binding strengths for different surfaces. On hydroxyapatite and silica surfaces, CsgB is the crucial element that determines the final adhesiveness of the CsgA-CsgB mixture. On the gold surface, on the other hand, CsgA controls the behavior of the mixture. Those findings uncover the binding behavior of curli proteins CsgA and CsgB on different biomedically valuable surfaces to obtain a more precise control on their adhesion to a targeted surface.

Curli of Uropathogenic Escherichia coli Enhance Urinary Tract Colonization as a Fitness Factor

Curli, a type of fimbriae widely distributed in uropathogenic Escherichia coli (UPEC), are involved in adhesion to human bladder cell surfaces and biofilm development. The role of UPEC curli was evaluated in a murine model of urinary tract infection. The aim of this study was to establish the role of curli in C57BL/6 mice transurethrally infected with curli-producing and non-curli-producing UPEC strains. We confirmed that curli enhanced UPEC colonization in the urinary tract, resulting in damage to both the bladder and kidney. Intranasal immunization with recombinant CsgA protein protected against colonization by curli-producing UPEC in the urinary tract. Quantification of cytokines from urinary tract organs showed increases in interleukin-6 and tumor necrosis factor (TNF) release in the kidneys 48 h postinfection with curli-producing UPEC. By contrast, mice infected with non-curli-producing UPEC showed the highest release of interleukin-6, -10, and -17A and TNF. Curli may obscure other fimbriae and LPS, preventing interactions with Toll-like receptors. When intranasal immunization with recombinant FimH and PapG proteins and subsequent infection with this strain were performed, cytokine quantification showed a decrease in the stimulation and release by the uroepithelium. Thus, curli are amyloid-like fimbriae that enhances colonization in the urinary tract and a possible fitness factor.

Uropathogenic Escherichia coli strains harboring tosA gene were associated to high virulence genes and a multidrug-resistant profile

TosA, a putative repeats-in-toxin protein that has recently gained importance as an antigenic molecule, has characteristics of nonfimbrial adhesins and can act as a virulence marker in uropathogenic Escherichia coli (UPEC) strains; however, little is known about the association of this protein with antibiotic resistance profiles in UPEC tosA⁺ clinical strains. The aim of this study was to evaluate UPEC tosA⁺ strains, including examining genetic diversity, associations with phylogenetic groups, resistance profiles, virulence genes, adherence assays, integrons, and extended-spectrum beta-lactamase phenotypes. Pulsed-field gel electrophoresis analysis grouped these strains into eight clusters with 62% genetic diversity. These strains were mainly associated with the multidrug-resistant profiles, together with an association with class 1 integron and the extended-spectrum beta-lactamase phenotype. Additionally, the strains exhibited a distribution of ≥96% for core-associated genes, while a variable distribution was identified for pathogenic islands-associated genes. Strong associations between UPEC tosA⁺ strains and two phylogenetic groups (B2 and D) were identified, including resistance to β-lactam and non-β-lactam antibiotics. The UPEC tosA⁺ clinical strains exhibited major adherence, which was related to the fitness and virulence genes. A recombinant TosA protein reacted with antibodies from the sera of urinary tract infection patients, and anti-recombinant TosA polyclonal antibodies also detected TosA expression in these strains. In conclusion, strains of UPEC tosA⁺ belonging to phylogenetic group B2 had a high frequency of fitness and virulence genes associated with class 1 integrons and the extended-spectrum beta-lactamase phenotype, which exhibited a high adherence profile. The TosA protein is expressed during infection with UPEC and is considered an immunogenic molecule.

Features of urinary Escherichia coli isolated from children with complicated and uncomplicated urinary tract infections in Mexico

The Hospital Infantil de México Federico Gómez (HIMFG) is a tertiary care hospital in Mexico City where Escherichia coli is frequently isolated from the urine samples of pediatric patients with urinary tract infections. A collection of 178 urinary Escherichia coli (UEc) isolates associated with complicated and uncomplicated urinary tract infections were evaluated in this study. The patterns of resistance to 9 antibiotic classes showed that 60.7% of the UEc isolates had a highly multidrug-resistant (MDR) profile. Genetic diversity analyses of the UEc isolates showed a high variability and revealed 16 clusters associated with four phylogenetic groups, namely, groups A, B1, B2, and D. Phylogenetic group B2 was widely associated with the 16 clusters as well as with virulence and fitness genes. The virulence and fitness genes in the UEc isolates, which included fimbriae-, siderophore-, toxin-, and mobility-associated genes, were grouped as occurring at a low, variable, or high frequency. Interestingly, only the papF gene could be amplified from some UEc isolates, and the sequence analysis of the pap operon identified an insertion sequence (IS) element and gene loss. These data suggested pathoadaptability and the development of immune system evasion, which was confirmed by the loss of P fimbriae-associated agglutination in the UEc isolates. E. coli clone O25-ST131 had a prevalence of 20.2% among the UEc isolates; these isolates displayed both a highly MDR profile and the presence of the papGII, fimH, papGIII, iutD, sat, hlyA, and motA genes. In conclusion, the UEc isolates from complicated urinary tract infection (cUTI) were characterized as being MDR, highly genetically diverse, and associated with phylogenetic group B2 and many virulence and fitness genes. Additionally, gene loss and IS elements were identified in some UEc isolates identified as clone O25-ST131.

Targeting Dynamical Binding Processes in the Design of Non-Antibiotic Anti-Adhesives by Molecular Simulation-The Example of FimH

Located at the tip of type I fimbria of Escherichia coli, the bacterial adhesin FimH is responsible for the attachment of the bacteria to the (human) host by specifically binding to highly-mannosylated glycoproteins located on the exterior of the host cell wall. Adhesion represents a necessary early step in bacterial infection and specific inhibition of this process represents a valuable alternative pathway to antibiotic treatments, as such anti-adhesive drugs are non-intrusive and are therefore unlikely to induce bacterial resistance. The currently available anti-adhesives with the highest affinities for FimH still feature affinities in the nanomolar range. A prerequisite to develop higher-affinity FimH inhibitors is a molecular understanding of the FimH-inhibitor complex formation. The latest insights in the formation process are achieved by combining several molecular simulation and traditional experimental techniques. This review summarizes how molecular simulation contributed to the current knowledge of the molecular function of FimH and the importance of dynamics in the inhibitor binding process, and highlights the importance of the incorporation of dynamical aspects in (future) drug-design studies.

Mannheimia haemolytica OmpP2-like is an amyloid-like protein, forms filaments, takes part in cell adhesion and is part of biofilms

Mannheimia haemolytica causes respiratory disease in cattle. Amyloid proteins are a major component of biofilms; they aid in adhesion and confer resistance against several environmental insults. The amyloid protein curli is highly resistant to protease digestion and physical and chemical denaturation and binds Congo red (CR) dye. The purpose of this study was to characterize an approximately 50-kDa CR-binding amyloid-like protein (ALP) expressed by M. haemolytica. This protein resisted boiling and formic acid digestion and was recognized by a polyclonal anti-Escherichia coli curli serum, suggesting its relationship with amyloid proteins. Immunolabeling and transmission electron microscopy showed that antibodies bound long, thin fibers attached to the bacterial surface. Mass spectrometry analysis indicated that these fibers are M. haemolytica OmpP2-like proteins. The purified protein formed filaments in vitro, and antiserum against it reacted positively with biofilms. An in silico analysis of its amino acid sequence indicated it has auto-aggregation properties and eight amyloid peptides. Rabbit polyclonal antibodies generated against this ALP diminished the adhesion of ATCC 31612 and BA1 M. haemolytica strains to A549 human epithelial cells, indicating its participation in cell adhesion. ALP expressed by M. haemolytica may be important in its pathogenicity and ability to form biofilms.