Role of motility in the colonization of uropathogenic Escherichia coli in the urinary tract

Bacterial clustering biomaterials as anti-infective therapies

In Nature, bacterial clustering by host-released peptides or nucleic acids is an evolutionarily conserved immune defense strategy employed to prevent adhesion of pathogenic microbes, which is prerequisite for most infections. Synthetic anti-adhesion strategies present as non-lethal means of targeting bacteria and may potentially be used to avoid resistance against antimicrobial therapies. From bacteria-agglutinating biomolecules discovered in nature to synthetic designs involving peptides, cationic polymers and nanoparticles, the modes of actions appear broad and unconsolidated. Herein, we present a critical review and update of the state-of-the-art in synthetic bacteria-clustering designs with proposition of a more streamlined nomenclature and classification. Overall, this review aims to consolidate the conceptual framework in the field of bacterial clustering and highlight its potentials as an avenue for discovering novel antibacterial biomaterials.

PotF Affects the Antibacterial Activity of Plantaricin BM-1 Against Escherichia coli K12 by Modulating Biofilm Formation and Cell Membrane Integrity

Plantaricin BM-1 exhibits antibacterial activity against Escherichia coli; however, the underlying mechanism remains unclear. This study aimed to investigate the function of PotF, a putrescine-binding protein, in regulating the antibacterial activity of plantaricin BM-1 against E. coli K12. The antibacterial activity of plantaricin BM-1 against E. coli K12 and JW0838 cells was assessed using growth curves. The differences in biofilm formation between the two E. coli strains were evaluated by crystal violet staining and confocal laser scanning microscopy. The effects of plantaricin BM-1 on E. coli morphology and cell membrane integrity were investigated by electron microscopy and lactate dehydrogenase release assays. Proteomics was used to screen for differentially expressed proteins (DEPs) that are potentially involved in regulating the antibacterial mechanism. The null mutation of potF enhanced the antibacterial effects of plantaricin BM-1 on E. coli, and caused a significant decrease (p < 0.05) in the biofilms of E. coli JW0838. The plantaricin disrupted the cell membrane of E. coli JW0838. Proteomic analysis revealed that potF mutation significantly affected several DEPs involved in biofilm formation. Plantaricin BM-1 exhibited significantly enhanced antibacterial activity against biofilm-associated gene mutants compared to wild-type E. coli K12. These findings enhance our understanding of the bacteriostasis of class IIa bacteriocins against Gram-negative microorganisms.

First report on the physicochemical and proteomic characterization of Proteus mirabilis outer membrane vesicles under urine-mimicking growth conditions: comparative analysis with Escherichia coli

Introduction

Uropathogenic bacteria employ multiple strategies to colonize the urinary tract, including biofilm formation, invasion of urothelial cells, and the production of adhesins, toxins, and siderophores. Among the most prevalent pathogens causing urinary tract infections (UTIs) are Uropathogenic Escherichia coli and Proteus mirabilis. A notable feature of Gram-negative bacteria is their ability to produce outer membrane vesicles (OMVs), which play critical roles in bacterial survival, virulence, and host-pathogen interactions, including UTIs.

Methods

In this study, OMVs were isolated and characterized from two clinical strains, E. coli U144 and P. mirabilis 2,921, cultured in both Luria-Bertani broth and artificial urine.

Result and discussion

The OMVs ranged in size from 85 to 260 nm, with the largest vesicles observed in artificial urine. Proteomic analysis allowed the identification of 282 proteins in OMVs from E. coli and 353 proteins from P. mirabilis when cultured LB medium, while 215 were identified from E. coli and 103 from P. mirabilis when cultured in artificial urine. The majority of these proteins originated from the bacterial envelope, while others were linked to motility and adhesion. Notably, the protein composition of OMVs varied depending on the growth medium, and proteins associated with zinc and iron uptake being more prominent in artificial urine, suggesting their importance in the urinary environment. Crucially, this is the first report to characterize P. mirabilis OMVs under different culture conditions, offering novel insights into the role of OMVs in UTI pathogenesis. These findings provide a deeper understanding of the molecular mechanisms by which OMVs contribute to bacterial virulence, establishing the foundation for potential therapeutic interventions targeting OMV-mediated processes in UTIs.

Antimicrobial and antibiofilm activities of halogenated phenols against Staphylococcus aureus and other microbes

Antimicrobial resistance is a global public health crisis that undermines the efficacy of treatments for infectious diseases, contributing to higher healthcare costs. Among Gram-positive bacteria, Staphylococcus aureus poses significant challenges due to its ability to develop resistance to multiple antibiotics, particularly in food and healthcare settings. Biofilm formation by S. aureus further enhances its resistance and pathogenicity. This study investigated the effects of 126 halogenated compounds on S. aureus biofilms, identifying five potent halogenated phenols. Among these, 2,4,6-triiodophenol (2,4,6-TIP) emerged as the most effective, exhibiting strong biofilm inhibition at a minimum inhibitory concentration (MIC) of 5 μg mL-1. Additionally, 2,4,6-TIP demonstrated efficacy against biofilms formed by methicillin-resistant S. aureus MW2 and various Gram-negative bacteria, including Vibrio parahaemolyticus and uropathogenic Escherichia coli (UPEC), as well as the fungal species Candida albicans. It also prevented the formation of polymicrobial biofilms involving S. aureus and C. albicans. Beyond its antibiofilm properties, 2,4,6-TIP was effective in controlling key virulence factors in S. aureus, such as metabolic, hemolysis and protease activities. It also reduced swimming motility in V. parahaemolyticus and UPEC, and impaired hyphal formation in C. albicans. Transcriptomic analysis further revealed that 2,4,6-TIP significantly repressed the gene expression of RNAIII, a key regulator of biofilm and virulence production in S. aureus. Furthermore, in silico analysis, plant and nematode models showed that 2,4,6-TIP exhibited reduced toxicity compared to phenol. These findings unveiled the strong antimicrobial potential of 2,4,6-TIP and suggest a broad-spectrum capacity to target the virulent characteristics of medically important pathogens. It also highlights that strategic halogenation may play a critical role in enhancing the activity of phenolic compounds while alleviating their toxicity profiles. t.

Comprehensive Genomic Analysis of Uropathogenic E. coli: Virulence Factors, Antimicrobial Resistance, and Mobile Genetic Elements

Our whole-genome sequencing analysis of sixteen uropathogenic E. coli isolates revealed a concerning picture of multidrug resistance and potentially virulent bacteria. All isolates belonged to four distinct clonal groups, with the highly prevalent ST131 lineage being associated with extensive antibiotic resistance and virulence factors. Notably, all isolates exhibited multidrug resistance, with some resistant to as many as 12 antibiotics. Fluoroquinolone resistance stemmed primarily from efflux pumps and mutations in gyrase and topoisomerase genes. Additionally, we identified genes encoding resistance to extended-spectrum cephalosporins, trimethoprim/sulfamethoxazole, and various heavy metals. The presence of diverse plasmids and phages suggests the potential for horizontal gene transfer and the dissemination of virulence factors. All isolates harbored genomic islands containing virulence factors associated with adhesion, biofilm formation, and invasion. Genes essential for iron acquisition, flagella biosynthesis, secretion systems, and toxin production were also prevalent. Adding further complexity to understanding the isolates' genetic makeup, we identified CRISPR-Cas systems. This study underscores the need for continued genomic surveillance in understanding the pathogenic mechanisms and resistance profiles of uropathogenic E. coli to aid in developing targeted therapeutic strategies.

Auranofin enhances the antibacterial effects of ertapenem against carbapenem-resistant Escherichia coli

The prevalence of carbapenem-resistant Escherichia coli (CREC) is increasing worldwide, and infections caused by CREC are associated with substantial morbidity and mortality rates. It is within this context that combination therapy has been reported as an effective strategy for treating resistant bacteria. Auranofin was approved by the FDA for treating rheumatoid arthritis. We confirmed that auranofin restored the susceptibility of ertapenem to CREC through synergy checkerboard and time-kill analyses. We also demonstrated that sub-MIC levels of auranofin significantly inhibited the expression of carbapenemase (blaKPC) and efflux pump (acrA, acrD, and tolC) genes. The combination of auranofin and ertapenem suppressed the expression levels of motility (motA and flhD) genes, decreasing motility, which is a known pathogenic factor in CREC. Taken together, our results indicate that auranofin exerted a synergistic effect with ertapenem by suppressing the expression of carbapenemase and efflux pump genes and reducing the motility and virulence factors against CREC.

Compensatory evolution of chromosomes and plasmids counteracts the plasmid fitness cost

Plasmids incur a fitness cost that has the potential to restrict the dissemination of resistance in bacterial pathogens. However, bacteria can overcome this disadvantage by compensatory evolution to maintain their resistance. Compensatory evolution can occur via both chromosomes and plasmids, but there are a few reviews regarding this topic, and most of them focus on plasmids. In this review, we provide a comprehensive overview of the currently reported mechanisms underlying compensatory evolution on chromosomes and plasmids, elucidate key targets regulating plasmid fitness cost, and discuss future challenges in this field. We found that compensatory evolution on chromosomes primarily arises from mutations in transcriptional regulatory factors, whereas compensatory evolution of plasmids predominantly involves three pathways: plasmid copy number regulation, conjugation transfer efficiency, and expression of antimicrobial resistance (AMR) genes. Furthermore, the importance of reasonable selection of research subjects and effective integration of diverse advanced research methods is also emphasized in our future study on compensatory mechanisms. Overall, this review establishes a theoretical framework that aims to provide innovative ideas for minimizing the emergence and spread of AMR genes.

Iron limitation induces motility in uropathogenic E. coli CFT073 partially through action of LpdA

More than half of women will experience a urinary tract infection (UTI) with most cases caused by uropathogenic Escherichia coli (UPEC). Bacterial swimming motility enhances UPEC pathogenicity, resulting in more severe disease outcomes including kidney infection. Surprisingly, the connection between motility and iron limitation is mostly unexplored despite the lack of free iron available in the host. We sought to investigate a potential connection between iron restriction and regulation of motility in UPEC. We cultured E. coli CFT073, a prototypical UPEC strain, under iron limitation and observed that CFT073 had elevated fliC (flagella) promoter activity, and this iron-specific response was repressed by the addition of exogenous iron. We confirmed increased flagellar expression in CFT073 by measuring fliC transcript, FliC protein, and surface-expressed flagella under iron-limited conditions. Interestingly, known motility regulator flhDC did not have altered transcription under these conditions. To define the regulatory mechanism of this response, we constructed single knockouts of eight master regulators and found the iron-regulated response was lost in crp, arcA, and fis mutants. Thus, we focused on the five genes regulated by all three regulators. Of the five genes knocked out, the iron-regulated motility response was most strongly dysregulated in the lpdA mutant, which also resulted in significantly lowered fitness in the murine model of ascending UTI, both against the WT and a non-motile fliC mutant. Collectively, we demonstrated that iron-mediated motility in CFT073 is partially regulated by lpdA, which contributes to the understanding of how uropathogens differentially regulate motility mechanisms in the iron-restricted host.

IMPORTANCE

Urinary tract infections (UTIs) are ubiquitous and responsible for over five billion dollars in associated health care costs annually. Both iron acquisition and motility are highly studied virulence factors associated with uropathogenic Escherichia coli (UPEC), the main causative agent of uncomplicated UTI. This work is innovative by providing mechanistic insight into the synergistic relationship between these two critical virulence properties. Here, we demonstrate that iron limitation has pleiotropic effects with consequences that extend beyond metabolism and impact other virulence mechanisms. Indeed, targeting iron acquisition as a therapy may lead to an undesirable enhancement of UPEC pathogenesis through increased motility. It is vital to understand the full breadth of UPEC pathogenesis to adequately respond to this common infection, especially with the increase of antibiotic-resistant pathogens.

Pseudomonas aeruginosa breaches respiratory epithelia through goblet cell invasion in a microtissue model

Pseudomonas aeruginosa, a leading cause of severe hospital-acquired pneumonia, causes infections with up to 50% mortality rates in mechanically ventilated patients. Despite some knowledge of virulence factors involved, it remains unclear how P. aeruginosa disseminates on mucosal surfaces and invades the tissue barrier. Using infection of human respiratory epithelium organoids, here we observed that P. aeruginosa colonization of apical surfaces is promoted by cyclic di-GMP-dependent asymmetric division. Infection with mutant strains revealed that Type 6 Secretion System activities promote preferential invasion of goblet cells. Type 3 Secretion System activity by intracellular bacteria induced goblet cell death and expulsion, leading to epithelial rupture which increased bacterial translocation and dissemination to the basolateral epithelium. These findings show that under physiological conditions, P. aeruginosa uses coordinated activity of a specific combination of virulence factors and behaviours to invade goblet cells and breach the epithelial barrier from within, revealing mechanistic insight into lung infection dynamics.

Peptidoglycan endopeptidase MepM of uropathogenic Escherichia coli contributes to competitive fitness during urinary tract infections

BACKGROUND

Urinary tract infections (UTIs) are common bacterial infections, primarily caused by uropathogenic Escherichia coli (UPEC), leading to significant health issues and economic burden. Although antibiotics have been effective in treating UPEC infections, the rise of antibiotic-resistant strains hinders their efficacy. Hence, identifying novel bacterial targets for new antimicrobial approaches is crucial. Bacterial factors required for maintaining the full virulence of UPEC are the potential target. MepM, an endopeptidase in E. coli, is involved in the biogenesis of peptidoglycan, a major structure of bacterial envelope. Given that the bacterial envelope confronts the hostile host environment during infections, MepM's function could be crucial for UPEC's virulence. This study aims to explore the role of MepM in UPEC pathogenesis.

RESULTS

MepM deficiency significantly impacted UPEC's survival in urine and within macrophages. Moreover, the deficiency hindered the bacillary-to-filamentous shape switch which is known for aiding UPEC in evading phagocytosis during infections. Additionally, UPEC motility was downregulated due to MepM deficiency. As a result, the mepM mutant displayed notably reduced fitness in causing UTIs in the mouse model compared to wild-type UPEC.

CONCLUSIONS

This study provides the first evidence of the vital role of peptidoglycan endopeptidase MepM in UPEC's full virulence for causing UTIs. MepM's contribution to UPEC pathogenesis may stem from its critical role in maintaining the ability to resist urine- and immune cell-mediated killing, facilitating the morphological switch, and sustaining motility. Thus, MepM is a promising candidate target for novel antimicrobial strategies.

TusDCB, a sulfur transferase complex involved in tRNA modification, contributes to UPEC pathogenicity

tRNA modifications play a crucial role in ensuring accurate codon recognition and optimizing translation levels. While the significance of these modifications in eukaryotic cells for maintaining cellular homeostasis and physiological functions is well-established, their physiological roles in bacterial cells, particularly in pathogenesis, remain relatively unexplored. The TusDCB protein complex, conserved in γ-proteobacteria like Escherichia coli, is involved in sulfur modification of specific tRNAs. This study focused on the role of TusDCB in the virulence of uropathogenic E. coli (UPEC), a bacterium causing urinary tract infections. The findings indicate that TusDCB is essential for optimal production of UPEC's virulence factors, including type 1 fimbriae and flagellum, impacting the bacterium's ability to aggregate in bladder epithelial cells. Deletion of tusDCB resulted in decreased virulence against urinary tract infection mice. Moreover, mutant TusDCB lacking sulfur transfer activity and tusE- and mnmA mutants revealed the indispensability of TusDCB's sulfur transfer activity for UPEC pathogenicity. The study extends its relevance to highly pathogenic, multidrug-resistant strains, where tusDCB deletion reduced virulence-associated bacterial aggregation. These insights not only deepen our understanding of the interplay between tRNA sulfur modification and bacterial pathogenesis but also highlight TusDCB as a potential therapeutic target against UPEC strains resistant to conventional antimicrobial agents.

Mapping niche-specific two-component system requirements in uropathogenic Escherichia coli

Sensory systems allow pathogens to differentiate between different niches and respond to stimuli within them. A major mechanism through which bacteria sense and respond to stimuli in their surroundings is two-component systems (TCSs). TCSs allow for the detection of multiple stimuli to lead to a highly controlled and rapid change in gene expression. Here, we provide a comprehensive list of TCSs important for the pathogenesis of uropathogenic Escherichia coli (UPEC). UPEC accounts for >75% of urinary tract infections (UTIs) worldwide. UTIs are most prevalent among people assigned female at birth, with the vagina becoming colonized by UPEC in addition to the gut and the bladder. In the bladder, adherence to the urothelium triggers E. coli invasion of bladder cells and an intracellular pathogenic cascade. Intracellular E. coli are safely hidden from host neutrophils, competition from the microbiota, and antibiotics that kill extracellular E. coli. To survive in these intimately connected, yet physiologically diverse niches E. coli must rapidly coordinate metabolic and virulence systems in response to the distinct stimuli encountered in each environment. We hypothesized that specific TCSs allow UPEC to sense these diverse environments encountered during infection with built-in redundant safeguards. Here, we created a library of isogenic TCS deletion mutants that we leveraged to map distinct TCS contributions to infection. We identify-for the first time-a comprehensive panel of UPEC TCSs that are critical for infection of the genitourinary tract and report that the TCSs mediating colonization of the bladder, kidneys, or vagina are distinct.IMPORTANCEWhile two-component system (TCS) signaling has been investigated at depth in model strains of Escherichia coli, there have been no studies to elucidate-at a systems level-which TCSs are important during infection by pathogenic Escherichia coli. Here, we report the generation of a markerless TCS deletion library in a uropathogenic E. coli (UPEC) isolate that can be leveraged for dissecting the role of TCS signaling in different aspects of pathogenesis. We use this library to demonstrate, for the first time in UPEC, that niche-specific colonization is guided by distinct TCS groups.

Microfluidic approaches in microbial ecology

Microbial life is at the heart of many diverse environments and regulates most natural processes, from the functioning of animal organs to the cycling of global carbon. Yet, the study of microbial ecology is often limited by challenges in visualizing microbial processes and replicating the environmental conditions under which they unfold. Microfluidics operates at the characteristic scale at which microorganisms live and perform their functions, thus allowing for the observation and quantification of behaviors such as growth, motility, and responses to external cues, often with greater detail than classical techniques. By enabling a high degree of control in space and time of environmental conditions such as nutrient gradients, pH levels, and fluid flow patterns, microfluidics further provides the opportunity to study microbial processes in conditions that mimic the natural settings harboring microbial life. In this review, we describe how recent applications of microfluidic systems to microbial ecology have enriched our understanding of microbial life and microbial communities. We highlight discoveries enabled by microfluidic approaches ranging from single-cell behaviors to the functioning of multi-cellular communities, and we indicate potential future opportunities to use microfluidics to further advance our understanding of microbial processes and their implications.

Adaptive evolution of plasmid and chromosome contributes to the fitness of a blaNDM-bearing cointegrate plasmid in Escherichia coli

Large cointegrate plasmids recruit genetic features of their parental plasmids and serve as important vectors in the spread of antibiotic resistance. They are now frequently found in clinical settings, raising the issue of how to limit their further transmission. Here, we conducted evolutionary research of a large blaNDM-positive cointegrate within Escherichia coli C600, and discovered that adaptive evolution of chromosome and plasmid jointly improved bacterial fitness, which was manifested as enhanced survival ability for in vivo and in vitro pairwise competition, biofilm formation, and gut colonization ability. From the plasmid aspect, large-scale DNA fragment loss is observed in an evolved clone. Although the evolved plasmid imposes a negligible fitness cost on host bacteria, its conjugation frequency is greatly reduced, and the deficiency of anti-SOS gene psiB is found responsible for the impaired horizontal transferability rather than the reduced fitness cost. These findings unveil an evolutionary strategy in which the plasmid horizontal transferability and fitness cost are balanced. From the chromosome perspective, all evolved clones exhibit parallel mutations in the transcriptional regulatory stringent starvation Protein A gene sspA. Through a sspA knockout mutant, transcriptome analysis, in vitro transcriptional activity assay, RT-qPCR, motility test, and scanning electron microscopy techniques, we demonstrated that the mutation in sspA reduces its transcriptional inhibitory capacity, thereby improving bacterial fitness, biofilm formation ability, and gut colonization ability by promoting bacterial flagella synthesis. These findings expand our knowledge of how cointegrate plasmids adapt to new bacterial hosts.

Antimicrobial and antibiofilm activities of chromone derivatives against uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) is a urinary tract pathogen responsible for most nosocomial urinary tract infections and can cause severe conditions like acute cystitis of the bladder or pyelonephritis. UPEC harbors a host of virulence factors like curli, hemolysin, siderophore, and motility factors and can form biofilm-like communities and quiescent reservoirs that aid its survival. This study was performed to investigate the antibiofilm, antimicrobial, and antivirulence potentials of three chromone derivatives, namely, 6-bromo 3-formylchromone, 6-chloro 3-formylchromone, and 3-formyl 6-isopropylchromone. These chromones had MICs against UPEC of 20, 20, and 50 µg/ml, respectively, inhibited biofilm formation by 72-96% at 20 µg/ml, and inhibited UPEC-associated virulence factors, that is, hemolysis, motility, curli, siderophore production, indole production, quiescent colony formation, and cell surface hydrophobicity. Gene expression analysis indicated these three derivatives downregulated virulence genes associated with toxins, biofilm production, and stress regulation and suggested they might target two-component UvrY response regulator. 3D-QSAR analysis showed that substitutions at the third and sixth positions of the chromone scaffold favor antimicrobial activity against UPEC. Furthermore, ADME profiles and C. elegans cytotoxicity assays indicated that these chromone derivatives are potent, safe drug candidates.

Characterization of uropathogenic Escherichia coli phylogroups associated with antimicrobial resistance, virulence factor distribution, and virulence-related phenotypes

In this study, we compared the characteristics of different uropathogenic Escherichia coli phylogroups. A total of 844 E. coli isolated from urine were enrolled and the antimicrobial susceptibility of E. coli to 22 antibiotics was determined by disk diffusion test. The distribution of phylogroups and 20 virulence factor genes was determined by PCR. Phenotypes associated with bacterial virulence, including motility, biofilm formation, and the production of curli and siderophore, were examined. Phylogroup B2 was dominant in our isolates (64.8%), followed by phylogroups D (8.6%), B1 (7.8%), F (6.0%), C (4.5%), A (3.1%), untypable (2.8%), E (1.8%), and clade I (0.5%). The prevalence of multidrug-resistant strains was highest in phylogroup C (86.8%), followed by E (80.0%), F (75.0%), and D (71.2%). Moreover, 23.5% of the phylogroup F E. coli were extensively drug-resistant. Phylogroup B2 E. coli had an average of the highest virulence factor genes (10.1 genes/isolate). Compared to phylogroup B2 E. coli, phylogroups F and clade I E. coli had higher motility while phylogroup C E. coli had lower motility. >60% of phylogroups A and C E. coli showed very low curli production. In contrast, 14%, 10%, and 7%, of E. coli in phylogroups F, B2, and E, produced a very high amount of curli, respectively. Surprisingly, phylogroup A E. coli showed the highest virulence to larvae, followed by phylogroups B2 and C. In summary, we first characterized and revealed that the antimicrobial resistance, virulence gene distribution, motility, and curli production, were associated with in E. coli phylogroups.

The PapB/FocB family protein TosR acts as a positive regulator of flagellar expression and is required for optimal virulence of uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) is a major causative agent of urinary tract infections. The bacteria internalize into the uroepithelial cells, where aggregate and form microcolonies. UPEC fimbriae and flagella are important for the formation of microcolonies in uroepithelial cells. PapB/FocB family proteins are small DNA-binding transcriptional regulators consisting of approximately 100 amino acids that have been reported to regulate the expression of various fimbriae, including P, F1C, and type 1 fimbriae, and adhesins. In this study, we show that TosR, a member of the PapB/FocB family is the activator of flagellar expression. The tosR mutant had similar expression levels of type 1, P and F1C fimbriae as the parent strain, but flagellar production was markedly lower than in the parent strain. Flagellin is a major component of flagella. The gene encoding flagellin, fliC, is transcriptionally activated by the sigma factor FliA. The fliA expression is induced by the flagellar master regulator FlhDC. The flhD and flhC genes form an operon. The promoter activity of fliC, fliA and flhD in the tosR mutant was significantly lower than in the parent strain. The purified recombinant TosR does not bind to fliC and fliA but to the upstream region of the flhD gene. TosR is known to bind to an AT-rich DNA sequence consisting of 29 nucleotides. The characteristic AT-rich sequence exists 550-578 bases upstream of the flhD gene. The DNA fragment lacking this sequence did not bind TosR. Furthermore, loss of the tosR gene reduced motility and the aggregation ability of UPEC in urothelial cells. These results indicate that TosR is a transcriptional activator that increases expression of the flhDC operon genes, contributing to flagellar expression and optimal virulence.

Seven-day Oral Intake of Orthosiphon stamineus Leaves Infusion Exerts Antiadhesive Ex Vivo Activity Against Uropathogenic E. coli in Urine Samples

Orthosiphon stamineus leaves (Java tea) extract is traditionally used for the treatment of urinary tract infections. According to recent in vitro data, animal infection studies, and transcriptomic investigations, polymethoxylated flavones from Java tea exert antiadhesive activity against uropathogenic Escherichia coli (UPEC). This antiadhesive activity has been shown to reduce bladder and kidney lesion in a mice infection model. As no data on the antivirulent activity of Java tea intake on humans are available, a biomedical study was performed on 20 healthy volunteers who self-administered Orthosiphon infusion (4 × 3 g per day, orally) for 7 days. The herbal material used for the study conformed to the specification of the European Pharmacopoeia, and ultra high-performance liquid chromatography (UHPLC) of the infusion showed rosmarinic acid, caffeic acid, and cichoric acid to be the main compounds aside from polymethoxylated flavones. Rosmarinic acid was quantified in the tea preparations with 243 ± 22 µg/mL, indicating sufficient reproducibility of the preparation of the infusion. Urine samples were obtained during the biomedical study on day 1 (control urine, prior to Java tea intake), 3, 6 and 8. Antiadhesive activity of the urine samples was quantified by flowcytometric assay using pre-treated UPEC NU14 and human T24 bladder cells. Pooled urine samples indicated significant inhibition of bacterial adhesion on day 3, 6 and 8. The urine samples had no influence on the invasion of UPEC into host cells. Bacterial proliferation was slightly reduced after 24 h incubation with the urine samples. Gene expression analysis (qPCR) revealed strong induction of fitness and motility gene fliC and downregulation of hemin uptake system chuT. These data correlate with previously reported datasets from in vitro transcriptomic analysis. Increased bacterial motility was monitored using a motility assay in soft agar with UPEC UTI89. The intake of Java tea had no effect on the concentration of Tamm-Horsfall Protein in the urine samples. The present study explains the antiadhesive and anti-infective effect of the plant extract by triggering UPEC from a sessile lifestyle into a motile bacterial form, with reduced adhesive capacity.

Role of Proteus mirabilis flagella in biofilm formation

Proteus mirabilis(P. mirabilis) is a common etiological agent of urinary tract infections, particularly those associated with catheterization. P. mirabilis efficiently forms biofilms on different surfaces and shows a multicellular behavior called 'swarming', mediated by flagella. To date, the role of flagella in P. mirabilis biofilm formation has been under debate. In this study, we assessed the role of P. mirabilis flagella in biofilm formation using an isogenic allelic replacement mutant unable to express flagellin. Different approaches were used, such as the evaluation of cell surface hydrophobicity, bacterial motility and migration across catheter sections, measurements of biofilm biomass and biofilm dynamics by immunofluorescence and confocal microscopy in static and flow models. Our findings indicate that P. mirabilis flagella play a role in biofilm formation, although their lack does not completely avoid biofilm generation. Our data suggest that impairment of flagellar function can contribute to biofilm prevention in the context of strategies focused on particular bacterial targets.

Urinary Tract Infections Caused by Uropathogenic Escherichia coli: Mechanisms of Infection and Treatment Options

Urinary tract infections (UTIs) are common bacterial infections that represent a severe public health problem. They are often caused by Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumonia), Proteus mirabilis (P. mirabilis), Enterococcus faecalis (E. faecalis), and Staphylococcus saprophyticus (S. saprophyticus). Among these, uropathogenic E. coli (UPEC) are the most common causative agent in both uncomplicated and complicated UTIs. The adaptive evolution of UPEC has been observed in several ways, including changes in colonization, attachment, invasion, and intracellular replication to invade the urothelium and survive intracellularly. While antibiotic therapy has historically been very successful in controlling UTIs, high recurrence rates and increasing antimicrobial resistance among uropathogens threaten to greatly reduce the efficacy of these treatments. Furthermore, the gradual global emergence of multidrug-resistant UPEC has highlighted the need to further explore its pathogenesis and seek alternative therapeutic and preventative strategies. Therefore, a thorough understanding of the clinical status and pathogenesis of UTIs and the advantages and disadvantages of antibiotics as a conventional treatment option could spark a surge in the search for alternative treatment options, especially vaccines and medicinal plants. Such options targeting multiple pathogenic mechanisms of UPEC are expected to be a focus of UTI management in the future to help combat antibiotic resistance.

Mapping Niche-specific Two-Component System Requirements in Uropathogenic Escherichia coli

Sensory systems allow pathogens to differentiate between different niches and respond to stimuli within them. A major mechanism through which bacteria sense and respond to stimuli in their surroundings is two-component systems (TCSs). TCSs allow for the detection of multiple stimuli to lead to a highly controlled and rapid change in gene expression. Here, we provide a comprehensive list of TCSs important for the pathogenesis of uropathogenic Escherichia coli (UPEC). UPEC accounts for >75% of urinary tract infections (UTIs) worldwide. UTIs are most prevalent among people assigned female at birth, with the vagina becoming colonized by UPEC in addition to the gut and the bladder. In the bladder, adherence to the urothelium triggers E. coli invasion of bladder cells and an intracellular pathogenic cascade. Intracellular E. coli are safely hidden from host neutrophils, competition from the microbiota, and antibiotics that kill extracellular E. coli. To survive in these intimately connected, yet physiologically diverse niches E. coli must rapidly coordinate metabolic and virulence systems in response to the distinct stimuli encountered in each environment. We hypothesized that specific TCSs allow UPEC to sense these diverse environments encountered during infection with built-in redundant safeguards. Here, we created a library of isogenic TCS deletion mutants that we leveraged to map distinct TCS contributions to infection. We identify - for the first time - a comprehensive panel of UPEC TCSs that are critical for infection of the genitourinary tract and report that the TCSs mediating colonization of the bladder, kidneys, or vagina are distinct.

Bacterial chemotaxis in human diseases

To infect and cause disease, bacterial pathogens must localize to specific regions of the host where they possess the metabolic and defensive acumen for survival. Motile flagellated pathogens exercise control over their localization through chemotaxis to direct motility based on the landscape of exogenous nutrients, toxins, and molecular cues sensed within the host. Here, we review advances in understanding the roles chemotaxis plays in human diseases. Chemotaxis drives pathogen colonization to sites of inflammation and injury and mediates fitness advantages through accessing host-derived nutrients from damaged tissue. Injury tropism may worsen clinical outcomes through instigating chronic inflammation and subsequent cancer development. Inhibiting bacterial chemotactic systems could act synergistically with antibacterial medicines for more effective and specific eradication.

In Vivo Role of Two-Component Regulatory Systems in Models of Urinary Tract Infections

Two-component signaling systems (TCSs) are finely regulated mechanisms by which bacteria adapt to environmental conditions by modifying the expression of target genes. In bacterial pathogenesis, TCSs play important roles in modulating adhesion to mucosal surfaces, resistance to antibiotics, and metabolic adaptation. In the context of urinary tract infections (UTI), one of the most common types infections causing significant health problems worldwide, uropathogens use TCSs for adaptation, survival, and establishment of pathogenicity. For example, uropathogens can exploit TCSs to survive inside bladder epithelial cells, sense osmolar variations in urine, promote their ascension along the urinary tract or even produce lytic enzymes resulting in exfoliation of the urothelium. Despite the usefulness of studying the function of TCSs in in vitro experimental models, it is of primary necessity to study bacterial gene regulation also in the context of host niches, each displaying its own biological, chemical, and physical features. In light of this, the aim of this review is to provide a concise description of several bacterial TCSs, whose activity has been described in mouse models of UTI.

Evasion of toll-like receptor recognition by Escherichia coli is mediated via population level regulation of flagellin production

Uropathogenic Escherichia coli is a major cause of urinary tract infections. Analysis of the innate immune response in immortalized urothelial cells suggests that the bacterial flagellar subunit, flagellin, is key in inducing host defenses. A panel of 48 clinical uro-associated E. coli isolates recovered from either cystitis, pyelonephritis asymptomatic bacteriuria (ABU) or UTI-associated bacteraemia infections were characterized for motility and their ability to induce an innate response in urothelial cells stably transfected with a NF-κB luciferase reporter. Thirty-two isolates (67%) were identified as motile with strains recovered from cystitis patients exhibiting an uneven motility distribution pattern; seven of the cystitis isolates were associated with a  > 5-fold increase in NF-κB signaling. To explore whether the NF-κB signaling response reflected antigenic variation, flagellin was purified from 14 different isolates. Purified flagellin filaments generated comparable NF-κB signaling responses, irrespective of either the source of the isolate or H-serotype. These data argued against any variability between isolates being related to flagellin itself. Investigations also argued that neither TLR4 dependent recognition of bacterial lipopolysaccharide nor growth fitness of the isolates played key roles in leading to the variable host response. To determine the roles, if any, of flagellar abundance in inducing these variable responses, flagellar hook numbers of a range of cystitis and ABU isolates were quantified. Images suggested that up to 60% of the isolate population exhibited flagella with the numbers averaging between 1 and 2 flagella per bacterial cell. These data suggest that selective pressures exist in the urinary tract that allow uro-associated E. coli strains to maintain motility, but exploit population heterogeneity, which together function to prevent host TLR5 recognition and bacterial killing.

Chemorepellent-Loaded Nanocarriers Promote Localized Interference of Escherichia coli Transport to Inhibit Biofilm Formation

To mitigate antimicrobial resistance, we developed polymeric nanocarrier delivery of the chemorepellent signaling agent, nickel, to interfere with Escherichia coli transport to a surface, an incipient biofilm formation stage. The dynamics of nickel nanocarrier (Ni NC) chemorepellent release and induced chemorepellent response required to effectively modulate bacterial transport for biofilm prevention were characterized in this work. Ni NCs were fabricated with the established Flash NanoPrecipitation method. NC size was characterized with dynamic light scattering. Measured with a zincon monosodium salt colorimetric assay, NC nickel release was pH-dependent, with 62.5% of total encapsulated nickel released at pH 7 within 0-15 min, competitive with rapid E. coli transport to the surface. Confocal laser scanning microscopy of E. coli (GFP-expressing) biofilm growth dynamics on fluorescently labeled Ni NC coated glass coupled with a theoretical dynamical criterion probed the biofilm prevention outcomes of NC design. The Ni NC coating significantly reduced E. coli attachment compared to a soluble nickel coating and reduced E. coli biomass area by 61% compared to uncoated glass. A chemical-in-plug assay revealed Ni NCs induced a chemorepellent response in E. coli. A characteristic E. coli chemorepellent response was observed away from the Ni NC coated glass over 10 μm length scales effective to prevent incipient biofilm surface attachment. The dynamical criterion provided semiquantitative analysis of NC mechanisms to control biofilm and informed optimal chemorepellent release profiles to improve NC biofilm inhibition. This work is fundamental for dynamical informed design of biofilm-inhibiting chemorepellent-loaded NCs promising to mitigate the development of resistance and interfere with the transport of specific pathogens.

Oscillatory rheotaxis of artificial swimmers in microchannels

Biological microswimmers navigate upstream of an external flow with trajectories ranging from linear to spiralling and oscillatory. Such a rheotactic response primarily stems from the hydrodynamic interactions triggered by the complex shapes of the microswimmers, such as flagellar chirality. We show here that a self-propelling droplet exhibits oscillatory rheotaxis in a microchannel, despite its simple spherical geometry. Such behaviour has been previously unobserved in artificial swimmers. Comparing our experiments to a purely hydrodynamic theory model, we demonstrate that the oscillatory rheotaxis of the droplet is primarily governed by both the shear flow characteristics and the interaction of the finite-sized microswimmer with all four microchannel walls. The dynamics can be controlled by varying the external flow strength, even leading to the rheotactic trapping of the oscillating droplet. Our results provide a realistic understanding of the behaviour of active particles navigating in confined microflows relevant in many biotechnology applications.

Flagella at the Host-Microbe Interface: Key Functions Intersect With Redundant Responses

Many bacteria and other microbes achieve locomotion via flagella, which are organelles that function as a swimming motor. Depending on the environment, flagellar motility can serve a variety of beneficial functions and confer a fitness advantage. For example, within a mammalian host, flagellar motility can provide bacteria the ability to resist clearance by flow, facilitate access to host epithelial cells, and enable travel to nutrient niches. From the host’s perspective, the mobility that flagella impart to bacteria can be associated with harmful activities that can disrupt homeostasis, such as invasion of epithelial cells, translocation across epithelial barriers, and biofilm formation, which ultimately can decrease a host’s reproductive fitness from a perspective of natural selection. Thus, over an evolutionary timescale, the host developed a repertoire of innate and adaptive immune countermeasures that target and mitigate this microbial threat. These countermeasures are wide-ranging and include structural components of the mucosa that maintain spatial segregation of bacteria from the epithelium, mechanisms of molecular recognition and inducible responses to flagellin, and secreted effector molecules of the innate and adaptive immune systems that directly inhibit flagellar motility. While much of our understanding of the dynamics of host-microbe interaction regarding flagella is derived from studies of enteric bacterial pathogens where flagella are a recognized virulence factor, newer studies have delved into host interaction with flagellated members of the commensal microbiota during homeostasis. Even though many aspects of flagellar motility may seem innocuous, the host’s redundant efforts to stop bacteria in their tracks highlights the importance of this host-microbe interaction.

Phytolectin conjugated positively charged fatty acid amide impairs virulence factors and inhibits cross-kingdom biofilm formation of Candida albicans and uropathogenic Escherichia coli

AIM

Polymicrobial biofilm encasing cross-kingdom microorganisms are apparent in medicine, which imposes serious resistance to conventional antimicrobial treatment. The objective of the study was to explore Butea monosperma seed lectin (BMSL) conjugated antimicrobial lipid, 2-((N-(2-hydroxyethyl)palmitamido)methyl)-1-methylpyridin-1-ium iodide (cN16E) to inhibit mixed-species biofilm of uropathogenic Escherichia coli-Candida albicans.

METHODS AND RESULTS

Antimicrobial activity and antibiofilm of cN16E and cN16E-BMSL conjugate (BcN16E) were analyzed against single- and mixed microbial cultures. The minimum inhibitory concentration (MIC) indicates that the MIC of cN16E-BMSL conjugate (BcN16E) against cohabiting UPEC-C. albicans was eightfold lower than the cN16E. BcN16E affects membrane integrity to elicit antimicrobial activity. BcN16E inhibits the dual-species biofilm even with 16 times lower MIC of cN16E. BcN16E impairs the biofilm-associated virulence factors which include extracellular polysaccharides, cell surface hydrophobicity, swimming, swarming motilities, hyphal filamentous morphology, curli formation, and hemolysin activity. As a proof of concept, we demonstrated BcN16E ability to inhibit dual-species biofilm formation on a urinary catheter.

CONCLUSION

The study revealed that the BcN16E is better than cN16E in impairing biofilm-associated virulence factors and exerting antimicrobial activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

The findings emphasize that phytolectin has the potential to enhance the anti-virulence strategies of antimicrobials against cross-kingdom biofilm-related infections.

Roles of the Tol/Pal System in Bacterial Pathogenesis and Its Application to Antibacterial Therapy

The Tol/Pal system (also written as “The Tol-Pal system”) is a set of protein complexes produced by most Gram-negative bacteria. It comprises the inner membrane-associated and the outer membrane-anchored subunits composed of the TolA, TolQ, and TolR proteins and the TolB and Pal proteins, respectively. Although the Tol/Pal system was first defined as bacterial proteins involved in colicin uptake of Escherichia coli, its global roles have been characterized in several studies as mentioned in this article. Pathogenesis of many Gram-negative pathogens is sustained by the Tol/Pal system. It is also essential for cell growth and fitness in some pathogens. Therefore, the Tol/Pal system is proposed as a potential target for antimicrobial chemotherapy. Although the tol/pal mutants are low in virulence, they still have the ability to stimulate the immune system. The Pal protein is highly immunogenic and induces both adaptive and innate immune responses. Therefore, the tol/pal mutant strains and Pal proteins also have potential vaccine properties. For these reasons, the Tol/Pal system represents a promising research target in the development of antibacterial therapeutic strategies for refractory infections caused by multi-drug-resistant (MDR), Gram-negative pathogens. In this paper, we summarize studies on the Tol/Pal system associated with bacterial pathogenesis and vaccine development.

Adaptive strategies of uropathogenic Escherichia coli CFT073: from growth in lab media to virulence during host cell adhesion

Urinary tract infections (UTIs) are a major concern in public health. The prevalent uropathogenic bacterium in healthcare settings is Escherichia coli. The increasing rate of antibiotic-resistant strains demands studies to understand E. coli pathogenesis to drive the development of new therapeutic approaches. This study compared the gene expression profile of selected target genes in the prototype uropathogenic E. coli (UPEC) strain CFT073 grown in Luria Bertani (LB), artificial urine (AU), and during adhesion to host bladder cells by semi-quantitative real-time PCR (RT-PCR) assays. AU effectively supported the growth of strain CFT073 as well as other E. coli strains with different lifestyles, thereby confirming the appropriateness of this medium for in vitro models. Unexpectedly, gene expression of strain CFT073 in LB and AU was quite similar; conversely, during the adhesion assay, adhesins and porins were upregulated, while key global regulators were downregulated with respect to lab media. Interestingly, fimH and papGII genes were significantly expressed in all tested conditions. Taken together, these results provide for the first time insights of the metabolic and pathogenic profile of strain CFT073 during the essential phase of host cell adhesion.

Antibacterial activity of medicinal plants against uropathogenic Escherichia coli

Urinary tract infections (UTIs) are one of the most common bacterial infections with uropathogenic Escherichia coli (UPEC) being the most prevalent causative agent in both complicated and uncomplicated UTIs. Antibiotic resistance among UPEC has been already demonstrated against a wide variety of antibiotics and the situation is continuing to deteriorate increasing the rate of recurrence and the difficulty of treatment and prophylaxis. Recently, a big attention has been paid to non-antibiotic approaches as an alternative to conventional antibiotics. Among many strategies, phytotherapy has gained a special attention worldwide. Herbal remedies have been used in traditional medicine since ancient times and they are well known for their effectiveness in treating many health conditions including UTIs. Researches are conducted continuously to validate the use of many medicinal plants against UPEC, investigate their mechanisms of action, and determine their active constituents. Our extensive review of the recent literature revealed that many phytochemicals are shown to target and inhibit a wide variety of bioprocesses in UPEC, such as adhesion, motility, biofilm formation, and quorum sensing. Such natural approaches are very promising in confronting the antibiotic resistance of UPEC and can be further used to develop plant-based strategies and pharmaceutical products to treat and prevent UTIs caused by UPEC.

ECTyper: in silico Escherichia coli serotype and species prediction from raw and assembled whole-genome sequence data

Escherichia coli is a priority foodborne pathogen of public health concern and phenotypic serotyping provides critical information for surveillance and outbreak detection activities. Public health and food safety laboratories are increasingly adopting whole-genome sequencing (WGS) for characterizing pathogens, but it is imperative to maintain serotype designations in order to minimize disruptions to existing public health workflows. Multiple in silico tools have been developed for predicting serotypes from WGS data, including SRST2, SerotypeFinder and EToKi EBEis, but these tools were not designed with the specific requirements of diagnostic laboratories, which include: speciation, input data flexibility (fasta/fastq), quality control information and easily interpretable results. To address these specific requirements, we developed ECTyper (https://github.com/phac-nml/ecoli_serotyping) for performing both speciation within Escherichia and Shigella, and in silico serotype prediction. We compared the serotype prediction performance of each tool on a newly sequenced panel of 185 isolates with confirmed phenotypic serotype information. We found that all tools were highly concordant, with 92-97 % for O-antigens and 98-100 % for H-antigens, and ECTyper having the highest rate of concordance. We extended the benchmarking to a large panel of 6954 publicly available E. coli genomes to assess the performance of the tools on a more diverse dataset. On the public data, there was a considerable drop in concordance, with 75-91 % for O-antigens and 62-90 % for H-antigens, and ECTyper and SerotypeFinder being the most concordant. This study highlights that in silico predictions show high concordance with phenotypic serotyping results, but there are notable differences in tool performance. ECTyper provides highly accurate and sensitive in silico serotype predictions, in addition to speciation, and is designed to be easily incorporated into bioinformatic workflows.

Multiple functions of flagellar motility and chemotaxis in bacterial physiology

Most swimming bacteria are capable of following gradients of nutrients, signaling molecules and other environmental factors that affect bacterial physiology. This tactic behavior became one of the most-studied model systems for signal transduction and quantitative biology, and underlying molecular mechanisms are well characterized in Escherichia coli and several other model bacteria. In this review, we focus primarily on less understood aspect of bacterial chemotaxis, namely its physiological relevance for individual bacterial cells and for bacterial populations. As evident from multiple recent studies, even for the same bacterial species flagellar motility and chemotaxis might serve multiple roles, depending on the physiological and environmental conditions. Among these, finding sources of nutrients and more generally locating niches that are optimal for growth appear to be one of the major functions of bacterial chemotaxis, which could explain many chemoeffector preferences as well as flagellar gene regulation. Chemotaxis might also generally enhance efficiency of environmental colonization by motile bacteria, which involves intricate interplay between individual and collective behaviors and trade-offs between growth and motility. Finally, motility and chemotaxis play multiple roles in collective behaviors of bacteria including swarming, biofilm formation and autoaggregation, as well as in their interactions with animal and plant hosts.

Comparative phenotypic characterization of hybrid Shiga toxin-producing / uropathogenic Escherichia coli, canonical uropathogenic and Shiga toxin-producing Escherichia coli

Hybrid Shiga toxin (Stx)-producing Escherichia coli (STEC) and uropathogenic E. coli (UPEC) strains are phylogenetically positioned between STEC and UPEC and can cause both diarrhea and urinary tract infections (UTIs). However, their virulence properties and adaptation to different host milieu in comparison to canonical UPEC and STEC strains are unknown. We determined phenotypes of the STEC/UPEC hybrid with respect to virulence including acid resistance, motility, biofilm formation, siderophore production, and adherence to human colonic Caco-2 and bladder T24 cells and compared to phenotypes of commensal strain MG1655, UPEC strain 536, and STEC strains B2F1 and Sakai. Moreover, we assessed the adaptation of the hybrid to artificial urine medium (AUM) and simulated colonic environment medium (SCEM). Overall acid resistance at pH 2.5 was high except in strains B2F1 and hybrid 05-00787 which showed reduced and extremely low acid resistance, respectively. Motility was reduced in hybrid 05-00787 and 09-05501 but strong in the remaining hybrids. While some hybrids showed high biofilm formation in LB, overall biofilm formation in SCEM and AUM were low and non-existent, respectively. All strains tested showed siderophore activity at equilibrium. All strains except MG1655 adhered to Caco-2 cells with the hybrid having similar adherence when compared to 536 but exhibited 2 and 3 times lower adherence when compared to B2F1 and Sakai, respectively. All Stx-producing strains adhered stronger to T24 cells than strains 536 and MG1655. Overall growth in LB, SCEM and AUM was consistent within the hybrid strains, except hybrid 05-00787 which showed significantly different growth patterns. Our data suggest that the hybrid is adapted to both, the intestinal and extraintestinal milieu. Expression of phenotypes typical of intestinal and extraintestinal pathogens thereby supports its potential to cause diarrhea and UTI.

Immunization with recombinant protein Ag43::UpaH with alum and 1,25(OH)2D3 adjuvants significantly protects Balb/C mice against urinary tract infection caused by uropathogenic Escherichia coli

The majority of urinary tract infections (UTIs) are caused by uropathogenic Escherichia coli (UPEC). Designing a vaccine will certainly reduce the occurrence of infection and antibiotic resistance of the isolates. Antigen 43 (Ag43) and autotransporter H (UpaH) have been associated with the virulence of UPEC. In the present study, the efficacy of different formulations of a hybrid protein composed of Ag43 and UpaH with and without alum and 1,25(OH)2D3 (Vitamin D3) adjuvants were evaluated in mice model. A significant increase in IgG and cellular responses was developed against Ag43::UpaH as compared to the control mice. The addition of alum or a mixture of alum and Vitamin D3 to the protein significantly enhanced the serum IgG responses and tended to remain in a steady state until 6 months. In addition, the mentioned formulations produced significant amounts of IgG1, IL-4, and IL-17 as compared to the fusion protein alone. In addition to the mentioned formulations, the combination of protein with Vitamin D3 also resulted in significantly higher serum IgA and IFN-γ levels as compared to the fusion protein alone. Mice immunized with fusion plus alum and formulation protein admixed with both alum and Vitamin D3 significantly reduced the bacterial load in the bladders and kidneys of mice as compared to the control. In this study, for the first time, the ability of a novel hybrid protein in combination with adjuvants alum and Vitamin D3 was evaluated against UPEC. Our results indicated that fusion Ag43::UpaH admixed with alum and Vitamin D3 could be a promising candidate against UTIs.

The RyfA small RNA regulates oxidative and osmotic stress responses and virulence in uropathogenic Escherichia coli

Urinary tract infections (UTIs) are a common bacterial infectious disease in humans, and strains of uropathogenic Escherichia coli (UPEC) are the most frequent cause of UTIs. During infection, UPEC must cope with a variety of stressful conditions in the urinary tract. Here, we demonstrate that the small RNA (sRNA) RyfA of UPEC strains is required for resistance to oxidative and osmotic stresses. Transcriptomic analysis of the ryfA mutant showed changes in expression of genes associated with general stress responses, metabolism, biofilm formation and genes coding for cell surface proteins. Inactivation of ryfA in UPEC strain CFT073 decreased urinary tract colonization in mice and the ryfA mutant also had reduced production of type 1 and P fimbriae (pili), adhesins which are known to be important for UTI. Furthermore, loss of ryfA also reduced UPEC survival in human macrophages. Thus, ryfA plays a key regulatory role in UPEC adaptation to stress, which contributes to UTI and survival in macrophages.

Roles of OmpX, an Outer Membrane Protein, on Virulence and Flagellar Expression in Uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) is a major pathogen that causes urinary tract infection (UTI). This bacterium adheres to and internalizes within urinary tract cells, where it aggregates and subsequently forms biofilm-like multicellular colonies that protect UPEC from antimicrobial agents and the host's immune system. Here, we show that OmpX, an outer membrane protein, plays a role in the pathogenesis of UPEC in renal cells. Deletion of ompX decreased bacterial internalization and aggregation within kidney epithelial cells and also impaired the colonization of mouse urinary tracts, but the ompX mutant still adhered to the epithelial cells at a level similar to that of the parent strain. FlhD, the master regulator of flagellum-related genes, had a low expression level in the ompX mutant compared to the parent strain, and the ompX mutant exhibited defective motility due to lower flagellar production than the parent strain. The fliC mutant, which lacks flagella, exhibited lower levels of bacterial internalization and aggregation than the parent strain. Additional deletion of ompX in the fliC mutant did not further decrease bacterial internalization. These combined results suggest that OmpX contributes to flagellar production in UPEC and then sustains UPEC virulence associated with bacterial internalization and aggregation within urinary tract cells and colonization in the urinary tract.

Chemotactic invasion in deep soft tissue by Vibrio vulnificus is essential for the progression of necrotic lesions

Necrotizing soft tissue infections (NSTI) progress to severe necrosis and result in fatal sepsis within a short time. Vibrio vulnificus is a causative agent and can spread from the initial infection site through soft tissue finally to the systemic circulation of the host. The motility and chemotaxis of this bacterium are essential for proliferation and lethality in a murine model of the infection, but their role in pathogenicity has not been characterized. In this study, we revealed the roles of motility and chemotaxis during the process of V. vulnificus infection. We compared a nonmotile mutant and two nonchemotactic mutants with their parent strain (WT) with regard to bacterial spread using an in vivo imaging system (IVIS) and invasion by detection of bacteria from the muscle and spleen of a murine infection model. WT rapidly spread throughout the infected thigh and invaded deep muscle causing severe tissue damage. The detection rate in the systemic circulation and the lethality were high. On the other hand, the nonmotile mutant stayed at the inoculation site, and the nonchemotactic mutants spread only slowly through the soft tissue of the infected thigh. Detection in the systemic circulation, the degree of tissue damage, and the lethality of nonchemotactic mutants were significantly reduced in mice compared with WT. This study demonstrated that chemotaxis is essential for invasion from the infection site to the deep and distant tissues and the main pathogenic factor for the rapid progression leading to sepsis in V. vulnificus NSTI.

Peptidoglycan Endopeptidase Spr of Uropathogenic Escherichia coli Contributes to Kidney Infections and Competitive Fitness During Bladder Colonization

Uropathogenic Escherichia coli (UPEC) is the most common pathogen of urinary tract infections (UTIs). Antibiotic therapy is the conventional measure to manage such infections. However, the rapid emergence of antibiotic resistance has reduced the efficacy of antibiotic treatment. Given that the bacterial factors required for the full virulence of the pathogens are potential therapeutic targets, identifying such factors may facilitate the development of novel therapeutic strategies against UPEC UTIs. The peptidoglycan (PG) endopeptidase Spr (also named MepS) is required for PG biogenesis in E. coli. In the present study, we found that Spr deficiency attenuated the ability of UPEC to infect kidneys and induced a fitness defect during bladder colonization in a mouse model of UTI. Based on the liquid chromatography (LC)/mass spectrometry (MS)/MS analysis of the bacterial envelope, spr deletion changed the levels of some envelope-associated proteins, suggesting that Spr deficiency interfere with the components of the bacterial structure. Among the proteins, FliC was significantly downregulated in the spr mutant, which is resulted in reduced motility. Lack of Spr might hinder the function of the flagellar transcriptional factor FlhDC to decrease FliC expression. The motility downregulation contributed to the reduced fitness in urinary tract colonization. Additionally, spr deletion compromised the ability of UPEC to evade complement-mediated attack and to resist intracellular killing of phagocytes, consequently decreasing UPEC bloodstream survival. Spr deficiency also interfered with the UPEC morphological switch from bacillary to filamentous shapes during UTI. It is known that bacterial filamentation protects UPEC from phagocytosis by phagocytes. In conclusion, Spr deficiency was shown to compromise multiple virulence properties of UPEC, leading to attenuation of the pathogen in urinary tract colonization and bloodstream survival. These findings indicate that Spr is a potential antimicrobial target for further studies attempting to develop novel strategies in managing UPEC UTIs.

Restoration of wild-type motility to flagellin-knockout Escherichia coli by varying promoter, copy number and induction strength in plasmid-based expression of flagellin

Flagellin is the major constituent of the flagellar filament and faithful restoration of wild-type motility to flagellin mutants may be beneficial for studies of flagellar biology and biotechnological exploitation of the flagellar system. However, gene complementation studies often fail to report whether true wild-type motility was restored by expressing flagellin from a plasmid. Therefore, we explored the restoration of motility by flagellin expressed from a variety of combinations of promoter, plasmid copy number and induction strength. Motility was only partially (~50%) restored using the tightly regulated rhamnose promoter due to weak flagellin gene expression, but wild-type motility was regained with the T5 promoter, which, although leaky, allowed titration of induction strength. The endogenous E. coli flagellin promoter also restored wild-type motility. However, flagellin gene transcription levels increased 3.1–27.9-fold when wild-type motility was restored, indicating disturbances in the flagellar regulatory mechanisms. Motility was little affected by plasmid copy number when dependent on inducible promoters. However, plasmid copy number was important when expression was controlled by the native E. coli flagellin promoter. Motility was poorly correlated with flagellin transcription levels, but strongly correlated with the amount of flagellin associated with the flagellar filament, suggesting that excess monomers are either not exported or not assembled into filaments. This study provides a useful reference for further studies of flagellar function and a simple blueprint for similar studies with other proteins.

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Restoration of motility to flagellin-knockout E. coli depends on choice of promoter.

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Plasmid copy number is important when using the natural flagellin promoter.

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For inducible promoters, induction strength is more important than copy number.

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Large increase in flagellin transcription but not flagella-associated protein.

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Plasmid-based expression interrupts flagellin expression control mechanisms.

YdiV regulates Escherichia coli ferric uptake by manipulating the DNA-binding ability of Fur in a SlyD-dependent manner

Iron is essential for all bacteria. In most bacteria, intracellular iron homeostasis is tightly regulated by the ferric uptake regulator Fur. However, how Fur activates the iron-uptake system during iron deficiency is not fully elucidated. In this study, we found that YdiV, the flagella gene inhibitor, is involved in iron homeostasis in Escherichia coli. Iron deficiency triggers overexpression of YdiV. High levels of YdiV then transforms Fur into a novel form which does not bind DNA in a peptidyl-prolyl cis-trans isomerase SlyD dependent manner. Thus, the cooperation of YdiV, SlyD and Fur activates the gene expression of iron-uptake systems under conditions of iron deficiency. Bacterial invasion assays also demonstrated that both ydiV and slyD are necessary for the survival and growth of uropathogenic E. coli in bladder epithelial cells. This reveals a mechanism where YdiV not only represses flagella expression to make E. coli invisible to the host immune system, but it also promotes iron acquisition to help E. coli overcome host nutritional immunity.

Restriction of chronic Escherichia coli urinary tract infection depends upon T cell-derived interleukin-17, a deficiency of which predisposes to flagella-driven bacterial persistence

Urinary tract infections (UTI) frequently progress to chronicity in infected individuals but the mechanisms of pathogenesis underlying chronic UTI are not well understood. We examined the role of interleukin (IL)-17A in UTI because this cytokine promotes innate defense against uropathogenic Escherichia coli (UPEC). Analysis of UPEC persistence and pyelonephritis in mice deficient in IL-17A revealed that UPEC CFT073 caused infection at a rate higher than the multidrug resistant strain EC958. Il17a^-/- mice exhibited pyelonephritis with kidney bacterial burdens higher than those of wild-type (WT) mice. Synthesis of IL-17A in the bladder reflected a combination of γδ-T and T_H 17 cell responses. Analysis of circulating inflammatory mediators at 24h postinoculation identified predictors of progression to chronicity, including IL-6 and monocyte chemoattractant protein-1 (MCP-1). Histological analysis identified infiltrating populations of neutrophils, NK cells, and γδ T cells in the bladder, whereas neutrophils predominated in the kidney. Analysis of the contribution of flagella to chronicity using hyper-flagellated and fliC-deficient UPEC in WT and Il17a^-/- mice revealed that, in a host that is deficient for the production of IL-17A, flagella contribute to bacterial persistence. These findings show a role for IL-17A in defense against chronic UTI and a contribution of flagella to the pathogenesis of infection.

Genomic Survey of E. coli From the Bladders of Women With and Without Lower Urinary Tract Symptoms

Urinary tract infections (UTIs) are one of the most common human bacterial infections. While UTIs are commonly associated with colonization by Escherichia coli, members of this species also have been found within the bladder of individuals with no lower urinary tract symptoms (no LUTS), also known as asymptomatic bacteriuria. Prior studies have found that both uropathogenic E. coli (UPEC) strains and E. coli isolates that are not associated with UTIs encode for virulence factors. Thus, the reason(s) why E. coli sometimes causes UTI-like symptoms remain(s) elusive. In this study, the genomes of 66 E. coli isolates from adult female bladders were sequenced. These isolates were collected from four cohorts, including women: (1) without lower urinary tract symptoms, (2) overactive bladder symptoms, (3) urgency urinary incontinence, and (4) a clinical diagnosis of UTI. Comparative genomic analyses were conducted, including core and accessory genome analyses, virulence and motility gene analyses, and antibiotic resistance prediction and testing. We found that the genomic content of these 66 E. coli isolates does not correspond with the participant's symptom status. We thus looked beyond the E. coli genomes to the composition of the entire urobiome and found that the presence of E. coli alone was not sufficient to distinguish between the urobiomes of individuals with UTI and those with no LUTS. Because E. coli presence, abundance, and genomic content appear to be weak predictors of UTI status, we hypothesize that UTI symptoms associated with detection of E. coli are more likely the result of urobiome composition.

Hyperglucosuria induced by dapagliflozin augments bacterial colonization in the murine urinary tract

AIM

To test the effects of dapagliflozin-induced hyperglucosuria on ascending bacterial urinary tract infection (UTI) in a mouse model.

METHODS

Dapagliflozin or canagliflozin was used to induce hyperglucosuria in non-diabetic adult female mice prior to transurethral inoculation with uropathogenic Escherichia coli (UPEC) or Klebsiella pneumoniae. Glucose, bacterial load, cytokines, neutrophil mobilization and inflammation during acute and chronic UTI were determined.

RESULTS

Significant increase in UPEC load was observed in the urinary tract of hyperglucosuric mice compared with controls. Dapagliflozin-treated mice developed bacteraemia resulting in UPEC colonization of the spleen and liver at a higher frequency than controls. Chronic UTI in hyperglucosuric mice resulted in an increased incidence of renal abscesses. Histopathological evaluation revealed only modest increases in tissue damage in the urinary bladders and kidneys of dapagliflozin-treated mice, despite a profound increase in bacterial load. There was poor neutrophil mobilization to the urine of hyperglucosuric mice. We also observed a delayed increase of IL-1β in urine, and bladders, and IL-6 in urine of hyperglucosuric mice. Experimental inoculation with K. pneumoniae also revealed higher bacterial burden in the urinary bladder, spleen and liver from dapagliflozin-treated mice compared with controls.

CONCLUSION

Collectively, our results indicate that dapagliflozin-induced hyperglucosuria in non-diabetic female mice leads to increased susceptibility to severe UTI, and bacteraemia of urinary tract origin.

The effect of flow on swimming bacteria controls the initial colonization of curved surfaces

The colonization of surfaces by bacteria is a widespread phenomenon with consequences on environmental processes and human health. While much is known about the molecular mechanisms of surface colonization, the influence of the physical environment remains poorly understood. Here we show that the colonization of non-planar surfaces by motile bacteria is largely controlled by flow. Using microfluidic experiments with Pseudomonas aeruginosa and Escherichia coli, we demonstrate that the velocity gradients created by a curved surface drive preferential attachment to specific regions of the collecting surface, namely the leeward side of cylinders and immediately downstream of apexes on corrugated surfaces, in stark contrast to where nonmotile cells attach. Attachment location and rate depend on the local hydrodynamics and, as revealed by a mathematical model benchmarked on the observations, on cell morphology and swimming traits. These results highlight the importance of flow on the magnitude and location of bacterial colonization of surfaces.

Bacterial colonization of surfaces has a profound environmental, technological and medical impact. Here, Secchi et al. show how fluid flow affects the magnitude and location of bacterial colonization on curved surfaces through its coupling with cell morphology and motility.

GadE regulates fliC gene transcription and motility in Escherichia coli

BACKGROUND

Escherichia coli (E. coli) express flagella to ascend human urinary tracts. To survive in the acidic pH of human urine, E. coli uses the glutamate decarboxylase acid response system, which is regulated by the GadE protein.

AIM

To determine if growth in an acidic pH environment affected fliC transcription and whether GadE regulated that transcription.

METHODS

A fliC-lacZ reporter fusion was created on a single copy number plasmid to assess the effects of acidic pH on fliC transcription. Further, a ΔgadE mutant strain of a uropathogenic E. coli was created and tested for motility compared to the wild-type strain.

RESULTS

Escherichia coli cells carrying the fliC-lacZ fusion displayed significantly less fliC transcription when grown in an acidic pH medium compared to when grown in a neutral pH medium. Transcription of fliC fell further when the E. coli was grown in an acidic pH/high osmolarity environment. Since GadE is a critical regulator of one acid response system, fliC transcription was tested in a gadE mutant strain grown under acidic conditions. Expression of fliC was derepressed in the E. coli gadE mutant strain grown under acidic conditions compared to that in wild-type bacteria under the same conditions. Furthermore, a gadE mutation in a uropathogenic E. coli background exhibited significantly greater motility than the wild-type strain following growth in an acidic medium.

CONCLUSION

Together, our results suggest that GadE may down-regulate fliC transcription and motility in E. coli grown under acidic conditions.

The novel E. coli cell division protein, YtfB, plays a role in eukaryotic cell adhesion

Characterisation of protein function based solely on homology searches may overlook functions under specific environmental conditions, or the possibility of a protein having multiple roles. In this study we investigated the role of YtfB, a protein originally identified in a genome-wide screen to cause inhibition of cell division, and has demonstrated to localise to the Escherichia coli division site with some degree of glycan specificity. Interestingly, YtfB also shows homology to the virulence factor OapA from Haemophilus influenzae, which is important for adherence to epithelial cells, indicating the potential of additional function(s) for YtfB. Here we show that E. coli YtfB binds to N’acetylglucosamine and mannobiose glycans with high affinity. The loss of ytfB results in a reduction in the ability of the uropathogenic E. coli strain UTI89 to adhere to human kidney cells, but not to bladder cells, suggesting a specific role in the initial adherence stage of ascending urinary tract infections. Taken together, our results suggest a role for YtfB in adhesion to specific eukaryotic cells, which may be additional, or complementary, to its role in cell division. This study highlights the importance of understanding the possible multiple functions of proteins based on homology, which may be specific to different environmental conditions.

The oxidative fumarase FumC is a key contributor for E. coli fitness under iron-limitation and during UTI

The energy required for a bacterium to grow and colonize the host is generated by metabolic and respiratory functions of the cell. Proton motive force, produced by these processes, drives cellular mechanisms including redox balance, membrane potential, motility, acid resistance, and the import and export of substrates. Previously, disruption of succinate dehydrogenase (sdhB) and fumarate reductase (frdA) within the oxidative and reductive tricarboxylic acid (TCA) pathways in uropathogenic E. coli (UPEC) CFT073 indicated that the oxidative, but not the reductive TCA pathway, is required for fitness in the urinary tract. Those findings led to the hypothesis that fumA and fumC encoding fumarase enzymes of the oxidative TCA cycle would be required for UPEC colonization, while fumB of the reductive TCA pathway would be dispensable. However, only UPEC strains lacking fumC had a fitness defect during experimental urinary tract infection (UTI). To further characterize the role of respiration in UPEC during UTI, additional mutants disrupting both the oxidative and reductive TCA pathways were constructed. We found that knock-out of frdA in the sdhB mutant strain background ameliorated the fitness defect observed in the bladder and kidneys for the sdhB mutant strain and results in a fitness advantage in the bladder during experimental UTI. The fitness defect was restored in the sdhBfrdA double mutant by complementation with frdABCD. Taken together, we demonstrate that it is not the oxidative or reductive pathway that is important for UPEC fitness per se, but rather only the oxidative TCA enzyme FumC. This fumarase lacks an iron-sulfur cluster and is required for UPEC fitness during UTI, most likely acting as a counter measure against exogenous stressors, especially in the iron-limited bladder niche.

Suppressing the phenotypic virulence factors of Uropathogenic Escherichia coli using marine polysaccharide

Uropathogenic Escherichia coli (UPEC) is one of the keystone pathogen that cause 80-90% of community acquired urinary tract infections (UTIs) and Catheter associated urinary tract infections (CAUTIs). Pathogenicity and ability of UPEC to colonize the bladder majorly relies on the expression of phenotypic virulence factors like flagella, pili, curli, and non pilus adhesion. Pathogens that colonize on the indwelling medical devices are able to communicate using quorum sensing (QS) signals. QS Plays a vital role in coordinating biofilm formation which results in the bacterial cells encased inside an extracellular polymeric substance (EPS). Chitosan is a marine polysaccharide which is known for its antibacterial activity. In the present study we investigated the ability of chitosan extracted from marine biowaste to mitigate the QS mediated biofilm formation in UPEC. Extracted chitosan (EC) and Commercial chitosan (CC) showed percentage inhibition of 80-85% and 60-75% respectively on young biofilm inhibition and preformed biofilm disruption. EC and CC were assessed for its ability to suppress QS mediated virulence in UPEC. Hemolysis assay showed a percentage inhibition of 79% against EC. Both chitosan showed profound activity to suppress the phenotypic virulence factors like swarming motility which is mediated by type I pili and colony morphology assay showed repression in cellulose production in UPEC. Furthermore, Real-Time PCR confirmed the ability of EC to down regulate the virulent genes which are responsible for invasion in UPEC. Accordingly, the current study foresees the quorum sensing inhibiting (QSI) potential of chitosan extracted from marine biowaste which offers an antibiotic free approach to combat UTI caused by UPEC.