A genetic basis of susceptibility to acute pyelonephritis

Recurrent urinary tract infection genetic risk: a systematic review and gene network analysis

INTRODUCTION AND HYPOTHESIS

The development of recurrent urinary tract infections (rUTIs) is not completely understood. This review is aimed at investigating the connection between genetics and rUTIs and summarizing the results of studies that have documented variations in gene expression among individuals with rUTIs compared with healthy individuals.

METHODS

A systematic search was conducted in Cochrane, Ovid, and PubMed, limiting the results to articles published between 1 January 2000, and 5 July 2022. Only studies comparing the difference in gene expression between individuals with rUTI and healthy individuals utilizing molecular techniques to measure gene expression in blood or urine samples were included in this systematic review. Gene network and pathways analyses were performed using Cytoscape software, with input data obtained from our systematic review of differentially expressed genes in rUTIs.

RESULTS

Six studies met our criteria for inclusion. The selected studies used molecular biology methods to quantify gene expression data from blood specimens. The analysis revealed that gene expressions of CXCR1 and TLR4 decreased, whereas CXCR2, TRIF, and SIGIRR increased in patients with rUTI compared with healthy controls. The analysis demonstrated that the most significant pathways were associated with TLR receptor signaling and tolerance, I-kappa B kinase/NF-kappa B signaling, and MyD88-independent TLR signaling.

CONCLUSIONS

This systematic review uncovered gene expression variations in several candidate genes and identified a number of underlying biological pathways associated with rUTIs. These findings could shift the treatment and prevention strategies for rUTIs.

Urinary Tract Infections: Renal Intercalated Cells Protect against Pathogens

Urinary tract infections affect more than 1 in 2 women during their lifetime. Among these, more than 10% of patients carry antibiotic-resistant bacterial strains, highlighting the urgent need to identify alternative treatments. While innate defense mechanisms are well-characterized in the lower urinary tract, it is becoming evident that the collecting duct (CD), the first renal segment encountered by invading uropathogenic bacteria, also contributes to bacterial clearance. However, the role of this segment is beginning to be understood. This review summarizes the current knowledge on CD intercalated cells in urinary tract bacterial clearance. Understanding the innate protective role of the uroepithelium and of the CD offers new opportunities for alternative therapeutic strategies.

A Systematic Review of the (Un)known Host Immune Response Biomarkers for Predicting Recurrence of Urinary Tract Infection

Recurrent urinary tract infections (rUTI) represent a major healthcare and economic burden along with a significant impact on patient’s morbidity and quality of life, even in the absence of well-known risk factors, such as vesicoureteral reflux. Despite numerous attempts to find a suitable therapeutic option, there is no clear benefit of any currently available intervention for prevention of UTI recurrence and its long-term consequences such as hypertension, renal scarring and/or insufficiency. The common treatment practice in many centers around the globe involves the use of continuous low-dose antibiotic prophylaxis, irrespective of various studies indicating increased microbial resistance against the prophylactic drug, leading to prolonged duration and escalating the cost of UTI treatment. Moreover, the rapid appearance of multi-drug resistant uropathogens is threatening to transform UTI to untreatable disease, while impaired host-microbiota homeostasis induced by a long-term use of antibiotics predisposes patients for various autoimmune and infectious diseases. New biomarkers of the increased risk of UTI recurrence could therefore assist in avoiding such outcomes by revealing more specific patient population which could benefit from additional interventions. In this light, the recent findings suggesting a crucial role of urothelial innate immunity mechanisms in protection of urinary tract from invading uropathogens might offer new diagnostic, prognostic and even therapeutic opportunities. Uroepithelial cells detect uropathogens via pattern recognition receptors, resulting in activation of intracellular signaling cascade and transcription factors, which ultimately leads to an increased production and secretion of chemokines, cytokines and antimicrobial peptides into the urinary stream. Emerging evidence suggest that the disturbance of a single component of the urinary tract innate immunity system might increase susceptibility for rUTI. The aim of the current review is to update clinicians and researchers on potential biomarkers of host immune response alterations predisposing for rUTI and propose those well worth exploring further. For this purpose, over a hundred original papers were identified through an extensive PubMed and Scopus databases search. This comprehensive review might enrich the current clinical practice and fill the unmet clinical needs, but also encourage the development of therapeutic agents that would facilitate urinary bacterial clearance by enhancing the host immune response.

Sociodemographic factors and uncomplicated pyelonephritis in women aged 15-50 years: a nationwide Swedish cohort register study (1997-2018)

OBJECTIVE

To study the relationship between sociodemographic factors and pyelonephritis.

METHODS

A nationwide open cohort study consisting of 2 052 873 women (76.2% Swedish-born) aged 15-50 years was conducted (1997-2018). The outcome was first event of acute uncomplicated pyelonephritis diagnosed in primary health care settings in relation to the sociodemographic factors. Cox regression models were used in the analyses.

RESULTS

The study identified 40 724 cases. In the fully adjusted model, women from non-western countries had higher risks of pyelonephritis compared to Swedish-born women. Women from Latin America/Caribbean had highest risk (Hazard ratio = 1.60; 95% CI 1.49-1.72), followed by Eastern Europe (HR = 1.26; 95% CI 1.21-1.32) and Middle East/North Africa (HR = 1.25; 95% CI 1.19-1.30). Low education, low income, urban living, and young age were also associated with higher risks of pyelonephritis.

CONCLUSION

This study presents novel risk factors associated with pyelonephritis. Women from non-western countries and with low socioeconomic status might suffer disproportionately from this serious infection. This might be due to biological predispositions and the fact that immigrant women do not acquire the same level of health or might receive less health care compared to native women, even in the presence of universal health care.

Molecular determinants of disease severity in urinary tract infection

The most common and lethal bacterial pathogens have co-evolved with the host. Pathogens are the aggressors, and the host immune system is responsible for the defence. However, immune responses can also become destructive, and excessive innate immune activation is a major cause of infection-associated morbidity, exemplified by symptomatic urinary tract infections (UTIs), which are caused, in part, by excessive innate immune activation. Severe kidney infections (acute pyelonephritis) are a major cause of morbidity and mortality, and painful infections of the urinary bladder (acute cystitis) can become debilitating in susceptible patients. Disease severity is controlled at specific innate immune checkpoints, and a detailed understanding of their functions is crucial for strategies to counter microbial aggression with novel treatment and prevention measures. One approach is the use of bacterial molecules that reprogramme the innate immune system, accelerating or inhibiting disease processes. A very different outcome is asymptomatic bacteriuria, defined by low host immune responsiveness to bacteria with attenuated virulence. This observation provides the rationale for immunomodulation as a new therapeutic tool to deliberately modify host susceptibility, control the host response and avoid severe disease. The power of innate immunity as an arbitrator of health and disease is also highly relevant for emerging pathogens, including the current COVID-19 pandemic.

Epidemiology, definition and treatment of complicated urinary tract infections

UTIs are amongst the most frequent bacterial infections. However, the clinical phenotypes of UTI are heterogeneous and range from rather benign, uncomplicated infections to complicated UTIs (cUTIs), pyelonephritis and severe urosepsis. Stratification of patients with UTIs is, therefore, important. Several classification systems exist for the description and classification of UTIs, with the common rationale that cUTIs have a higher risk of recurrence or chronification, progression or severe outcome than uncomplicated UTIs. The pathophysiology and treatment of cUTIs and pyelonephritis are driven more by host factors than by pathogen attributes. cUTIs and pyelonephritis are associated with high antimicrobial resistance rates among causative pathogens. However, antimicrobial resistance rates can differ substantially, depending on the population being studied and whether the data being analysed are from surveillance studies, registry data or interventional studies, in which specific inclusion and exclusion criteria are used for patient selection. For example, antibiotic resistance rates are higher in patients with urosepsis than in those with less severe infections. Thus, treatment outcomes differ substantially among studies, ranging from 50% to almost 100% clearance of infection, depending on the patient population analysed, the UTI entities included and the primary outcome of the study. Pyelonephritis and cUTIs have emerged as infection models for the study of novel antibiotics, including extensive investigation of novel substances active against Gram-negative bacteria.

The immune response to infection in the bladder

The bladder is continuously protected by passive defences such as a mucus layer, antimicrobial peptides and secretory immunoglobulins; however, these defences are occasionally overcome by invading bacteria that can induce a strong host inflammatory response in the bladder. The urothelium and resident immune cells produce additional defence molecules, cytokines and chemokines, which recruit inflammatory cells to the infected tissue. Resident and recruited immune cells act together to eradicate bacteria from the bladder and to develop lasting immune memory against infection. However, urinary tract infection (UTI) is commonly recurrent, suggesting that the induction of a memory response in the bladder is inadequate to prevent reinfection. Additionally, infection seems to induce long-lasting changes in the urothelium, which can render the tissue more susceptible to future infection. The innate immune response is well-studied in the field of UTI, but considerably less is known about how adaptive immunity develops and how repair mechanisms restore bladder homeostasis following infection. Furthermore, data demonstrate that sex-based differences in immunity affect resolution and infection can lead to tissue remodelling in the bladder following resolution of UTI. To combat the rise in antimicrobial resistance, innovative therapeutic approaches to bladder infection are currently in development. Improving our understanding of how the bladder responds to infection will support the development of improved treatments for UTI, particularly for those at risk of recurrent infection.

DCHS1 DNA copy number loss associated with pediatric urinary tract infection risk

Urinary tract infections (UTI), associated with vesicoureteral reflux (VUR), can lead to chronic kidney disease. Genetic alterations in the innate immune defenses contribute to UTI risk. We investigated a novel gene, Dachsous Cadherin-Related 1 (DCHS1), in children with UTI. We determined absolute DNA copy number (CN) of DCHS1 in children with UTI. In this case-control study, we utilized multiple complementary methods to determine the genomic CN of DCHS1. Children with (n = 370) and without (n = 71) VUR from two well-phenotyped clinical trials of UTI were copy-typed and compared to 491 healthy controls with no known history of VUR or UTI. Less than 1% of controls had a single copy of DCHS1, while 31% of children with UTI and no VUR and 7% of children with UTI and VUR had a single copy of the DCHS1 gene. Using immunostaining, we localized expression postnatally to the bladder and renal epithelia. Mice were also challenged with two uropathogenic Escherichia coli strains, and Dchs1 mRNA was quantified. This study represents the first report of DCHS1 in association with pediatric UTI. We hypothesize that its role in innate immunity is critical to lower urinary tract defense. Further investigation is required to determine the role of DCHS1 in innate immunity.

Urinary tract infection in pediatrics: an overview

OBJECTIVE

This review aimed to provide a critical overview on the pathogenesis, clinical findings, diagnosis, imaging investigation, treatment, chemoprophylaxis, and complications of urinary tract infection in pediatric patients.

SOURCE OF DATA

Data were obtained independently by two authors, who carried out a comprehensive and non-systematic search in public databases.

SUMMARY OF FINDINGS

Urinary tract infection is the most common bacterial infection in children. Urinary tract infection in pediatric patients can be the early clinical manifestation of congenital anomalies of the kidney and urinary tract (CAKUT) or be related to bladder dysfunctions. E. coli is responsible for 80-90% of community-acquired acute pyelonephritis episodes, especially in children. Bacterial virulence factors and the innate host immune systems may contribute to the occurrence and severity of urinary tract infection. The clinical presentation of urinary tract infections in children is highly heterogeneous, with symptoms that can be quite obscure. Urine culture is still the gold standard for diagnosing urinary tract infection and methods of urine collection in individual centers should be determined based on the accuracy of voided specimens. The debate on the ideal imaging protocol is still ongoing and there is tendency of less use of prophylaxis. Alternative measures and management of risk factors for recurrent urinary tract infection should be emphasized. However, in selected patients, prophylaxis can protect from recurrent urinary tract infection and long-term consequences. According to population-based studies, hypertension and chronic kidney disease are rarely associated with urinary tract infection.

CONCLUSION

Many aspects regarding urinary tract infection in children are still matters of debate, especially imaging investigation and indication of antibiotic prophylaxis. Further longitudinal studies are needed to establish tailored approach of urinary tract infection in childhood.

Association of mRNA Levels of IL6, MMP-8, GSS in Saliva and Pyelonephritis in Children

Nowadays, saliva is a subject of growing scientific interest because of its definite advantages as diagnostic medium. The aim of our study was to investigate the diagnostic potential and reliability of messenger RNAs (mRNAs) of selected genes—interleukin-6 (IL-6), matrix metalloproteinase-8 (MMP-8) and glutathione synthetase (GSS)—as salivary markers in children with diagnosed pyelonephritis and to correlate their levels with typical urine para-clinical indicators of the disease. Analysis of the mRNA levels for IL-6, MMP-8 and GSS in 28 children hospitalized with the diagnosis of pyelonephritis was conducted applying the method of quantitative reverse transcription polymerase chain reaction (RT-qPCR). In the study group (n = 28), IL-6 mRNA levels demonstrated 64-fold increase (p < 0.001). MMP-8 and GSS mRNA levels were increased in 12 samples in patients with pyelonephritis 3.27 (p < 0.01) and 1.94 (p < 0.001) times, respectively. We found a strong and significant correlation (p < 0.001) between the investigated mRNA for IL-6 and MMP-8, IL-6 and GSS, MMP-8 and GSS. Moderate degree of correlation was established between IL-6 and the typical para-clinical indicator of leucocytes (0.43, p < 0.05) and between GSS and leucocytes (0.54, p < 0.01). Salivary IL-6, MMP-8 and GSS mRNA levels in combination with urine test analysis could be useful diagnostic tool for the very distributed disorder of pyelonephritis in childhood.

Updates on urinary tract infections in kidney transplantation

Urinary tract infection (UTI) represents the most common infection after kidney transplantation; it is associated with an increased risk for acute kidney rejection and impaired graft function in the early post-transplant period. Kidney transplant recipients with UTIs are often clinically asymptomatic due to the immunosuppressive therapy; however, asymptomatic bacteriuria may progress to acute pyelonephritis, bacteremia and urosepsis, particularly in the early post-transplant period, that are independent risk factors for short and long-term graft and patient survival. This article reviews the definitions, incidence, risk factors and the management of UTI in kidney transplant recipients; furthermore, the main controversial and still unanswered questions, regarding the causes of recurrent UTIs, adequate use of antibiotics to avoid antibiotic resistance, dosing and timing for prophylaxis and treatment of symptomatic infections, are also discussed. The emerging definition of urinary microbiota introduces new concepts in understanding the complexity of the disease and might represent the future target for therapeutic interventions.

Association between interleukin 8-receptor gene (CXCR1 and CXCR2) polymorphisms and urinary tract infection: Evidence from 4097 subjects

AIM

The aim of this study was to determine whether a correlation exists between interleukin-8 receptor polymorphisms and urinary tract infection (UTI) susceptibility.

METHODS

We systematically searched electronic databases including PubMed, Embase, China National Knowledge Infrastructure, and Web of Science up to 5 November 2017 to select appropriate studies that focused on C-X-C chemokine receptor type 1 and/or 2 (CXCR1, CXCR2) polymorphisms with susceptibility to UTI. Eight case-control studies including 2085 patients with UTI and 2012 controls were enrolled in this study. Seven studies of CXCR1 rs2234671 and two studies of rs3138086 were included in the meta-analyses. Pooled odds ratio (OR) and corresponding 95% confidence interval (CI) were synthesized using fixed-effects or random-effects model according to heterogeneity.

RESULTS

No significant correlations were found between CXCR1 rs2234671 and rs3138086 polymorphisms and UTI susceptibility. However, subgroup analysis showed that rs2234671 was associated with an increased risk of UTI under allelic comparisons (C vs. G, OR = 1.95, 95% CI = 1.07-3.55), heterozygous model (GC vs. GG, OR = 1.93, 95% CI = 1.06-3.50), and dominant model (GC + CC vs. GG, OR = 1.98, 95% CI = 1.07-3.69) in children, especially in paediatric patients with acute pyelonephritis (allelic, OR = 2.43, 95% CI = 1.28-4.60; heterozygous, OR = 2.40, 95% CI = 1.24-4.62; dominant, OR = 2.48, 95% CI = 1.26-4.88). Furthermore, these results remained the same after eliminating paediatric patients with vesicoureteral reflux.

CONCLUSION

CXCR1 rs2234671 polymorphism might be associated with an increased risk of UTI in children.

Susceptibility to Urinary Tract Infection: Benefits and Hazards of the Antibacterial Host Response

A paradigm shift is needed to improve and personalize the diagnosis of infectious disease and to select appropriate therapies. For many years, only the most severe and complicated bacterial infections received more detailed diagnostic and therapeutic attention as the efficiency of antibiotic therapy has guaranteed efficient treatment of patients suffering from the most common infections. Indeed, treatability almost became a rationale not to analyze bacterial and host parameters in these larger patient groups. Due to the rapid spread of antibiotic resistance, common infections like respiratory tract- or urinary-tract infections (UTIs) now pose new and significant therapeutic challenges. It is fortunate and timely that infectious disease research can offer such a wealth of new molecular information that is ready to use for the identification of susceptible patients and design of new suitable therapies. Paradoxically, the threat of antibiotic resistance may become a window of opportunity, by encouraging the implementation of new diagnostic and therapeutic approaches. The frequency of antibiotic resistance is rising rapidly in uropathogenic organisms and the molecular and genetic understanding of UTI susceptibility is quite advanced. More bold translation of the new molecular diagnostic and therapeutic tools would not just be possible but of great potential benefit in this patient group. This chapter reviews the molecular basis for susceptibility to UTI, including recent advances in genetics, and discusses the consequences for diagnosis and therapy. By dissecting the increasingly well-defined molecular interactions between bacteria and host and the molecular features of excessive bacterial virulence or host-response malfunction, it is becoming possible to isolate the defensive from the damaging aspects of the host response. Distinguishing "good" from "bad" inflammation has been a long-term quest of biomedical science and in UTI, patients need the "good" aspects of the inflammatory response to resist infection while avoiding the "bad" aspects, causing chronicity and tissue damage.

Urinary NGAL deficiency in recurrent urinary tract infections

INTRODUCTION

Children with recurrent urinary tract infections (rUTI) often show no identifiable cause of their infections. Neutrophil gelatinase-associated lipocalin (NGAL) is known to be upregulated within the uroepithelium and kidney of patients with UTI and exhibits a localized bacteriostatic effect through iron chelation. We hypothesize that some patients with rUTI without an identifiable cause of their recurrent infections have locally deficient NGAL production. We therefore explored whether a lack of NGAL production may be a factor in the pathogenesis of rUTI.

MATERIALS AND METHODS

Patients seen in the urology clinic for rUTI who were <21 years of age were enrolled. Patients were excluded if they had UTI at the time of enrollment, evidence of renal disease, decreased renal function, known anatomic abnormality of the genitourinary tract, or other reasons that predispose to UTI, such as neurogenic bladder, the need for intermittent catheterization, or unrepaired posterior urethral valves. Control patients were healthy children enrolled from the emergency department with no history of UTI or renal dysfunction, normal urinalysis at the time of enrollment, and presenting no diagnosis associated with increased NGAL levels, such as acute kidney injury or infection. NGAL was measured by immunoblot.

RESULTS

Fifteen cases and controls were enrolled. Median urinary NGAL levels were significantly decreased in rUTI patients compared with controls [15 (14-29) ng/ml vs 30 (27-61) ng/ml; p = 0.002)] Although comparatively diminished, measurable NGAL levels were present in all patients with rUTI.

CONCLUSIONS

Urinary NGAL is significantly decreased in patients with compared with patients without rUTI. These data suggest that some patients with rUTI may be predisposed to UTI because of a relative local deficiency in urinary NGAL production.

[Pathogenesis of urinary tract infections : An update]

Urinary tract infections are among the most common bacterial infections worldwide. The management has become a public health concern of socioeconomic importance. Every second woman will experience at least one episode in her lifetime. Due to the emergence of multiresistant pathogens and the developmental void, treatment has become more challenging over the years. Deciphering the complex molecular interaction between host and pathogen is necessary to identify potent treatment targets for future approaches. The objective of this review is to present novel aspects on the pathogenesis of urinary tract infections and its relevance for clinical practice.

Estimation of the relationship between the polymorphisms of selected genes: ACE, AGTR1, TGFβ1 and GNB3 with the occurrence of primary vesicoureteral reflux

PURPOSE

Etiopathogenesis of VUR is composite and not fully understood. Many data indicate the importance of genetic predisposition. The aim of this study was to establish the relationship of selected polymorphisms: 14094 polymorphism of the ACE, polymorphism rs1800469 of TGFβ-1, rs5443 gene polymorphism of the GNB3 and receptor gene polymorphism rs5186 type 1 AGTR1 with the occurrence of the primary vesicoureteral reflux.

MATERIAL

The study included 190 children: 90 with the primary VUR confirmed with the voiding cystourethrogram and excluded secondary VUR and a control group of 100 children without a history of the diseases of the genitourinary tract.

METHODS

The study was planned in the scheme: "tested case versus control." Genomic DNA was isolated from the leukocytes of peripheral blood samples. The results were statistically analyzed in the Statistica 10 using χ ² test and analysis of the variance Anova.

RESULTS

Any of the four studied polymorphisms showed no difference in the distribution of genotypes between patients with primary vesicoureteral reflux and the control group. In patients with VUR and TT genotype polymorphism rs5443 GNB3 gene, the glomerular filtration rate was significantly higher than in patients with genotype CC or CT.

CONCLUSIONS

(1) No relationship was found between the studied polymorphisms (14094 ACE gene, rs1800469 gene TGFβ1, GNB3 gene rs5443, rs5186 AGTR1 gene) and the occurrence of primary vesicoureteral reflux. (2) TT genotype polymorphism rs5443 GNB3 gene may be a protective factor for the improved renal function in patients with primary vesicoureteral reflux in patients with genotype CC or CT.

CXCR1-mediated neutrophil degranulation and fungal killing promote Candida clearance and host survival

Systemic Candida albicans infection causes high morbidity and mortality and is now the leading cause of nosocomial bloodstream infection in the United States. Neutropenia is a major risk factor for poor outcome in infected patients; however, the molecular factors that mediate neutrophil trafficking and effector function during infection are poorly defined. Using a mouse model of systemic candidiasis, we found that the neutrophil-selective CXC chemokine receptor Cxcr1 and its ligand, Cxcl5, are highly induced in the Candida-infected kidney, the target organ in the model. To investigate the role of Cxcr1 in antifungal host defense in vivo, we generated Cxcr1(-/-) mice and analyzed their immune response to Candida. Mice lacking Cxcr1 exhibited decreased survival with enhanced Candida growth in the kidney and renal failure. Increased susceptibility of Cxcr1(-/-) mice to systemic candidiasis was not due to impaired neutrophil trafficking from the blood into the infected kidney but was the result of defective killing of the fungus by neutrophils that exhibited a cell-intrinsic decrease in degranulation. In humans, the mutant CXCR1 allele CXCR1-T276 results in impaired neutrophil degranulation and fungal killing and was associated with increased risk of disseminated candidiasis in infected patients. Together, our data demonstrate a biological function for mouse Cxcr1 in vivo and indicate that CXCR1-dependent neutrophil effector function is a critical innate protective mechanism of fungal clearance and host survival in systemic candidiasis.

The Genetics of Urinary Tract Infections and the Innate Defense of the Kidney and Urinary tract

The urinary tract is a sterile organ system. Urinary tract infections (UTIs) are common and often serious infections. Research has focused on uropathogen, environment, and host factors leading to UTI pathogenesis. A growing body of evidence exists implicating genetic factors that can contribute to UTI risks. In this review, we highlight genetic variations in aspects of the innate immune system critical to the host response to uropathogens. This overview includes genetic variations in pattern recognition receptor molecules, chemokines/cytokines, and neutrophil activation. We also comprehensively cover murine knockout models of UTI, genetic variations involved in renal scarring as a result of ascending UTIs, and asymptomatic bacteriuria.

Urinary tract infection pattern in adult women followed from childhood

BACKGROUND

The aim of this study was to describe the pattern of urinary tract infection (UTI) and bladder function in women who had experienced recurrent UTI in childhood, with and without consequent renal damage, and followed for three to four decades.

METHODS

A population-based cohort of women who had been followed from the first UTI in childhood and previously studied at a median age of 27 years was studied at a median age of 41 years. Renal damage was evaluated by (99m)Tc-dimercaptosuccinic acid scan. Clinical data were collected on the pattern of recurrent UTIs and bladder function.

RESULTS

A total of 86 women were investigated, of whom 58 had suffered renal damage and 28 were without. Febrile UTI in adulthood had occurred in 22 patients, once in 15 women and twice or more in seven women. There was a change in the infection pattern over time, evident already in childhood, that was characterized by a decrease in UTI frequency and a shift from febrile to non-febrile infections. A significant association was found between renal damage and febrile UTI (p = 0.046), and between abnormal bladder function and recurrent non-febrile UTI (p = 0.002). There was no relationship between persisting vesicoureteral reflux (VUR) and proneness to either symptomatic UTI (p = 0.99) or febrile UTI in adulthood (p = 0.14).

CONCLUSIONS

Among this study cohort there was a continuously decreasing rate of febrile UTI in adulthood. Persisting VUR was not related to UTI in adulthood. Abnormal bladder function was related to non-febrile UTI but not to febrile UTI.

Urinary Tract Infection Molecular Mechanisms and Clinical Translation

Rapid developments in infection biology create new and exciting options for individualized diagnostics and therapy. Such new practices are needed to improve patient survival and reduce morbidity. Molecular determinants of host resistance to infection are being characterized, making it possible to identify susceptible individuals and to predict their risk for future morbidity. Immunotherapy is emerging as a new strategy to treat infections worldwide and controlled boosting of the host immune defense represents an important therapeutic alternative to antibiotics. In proof of concept studies, we have demonstrated that this approach is feasible. The long-term goal is not just to remove the pathogens but to also develop technologies that restore resistance to infection in disease-prone patients and devise personalized therapeutic interventions. Here, we discuss some approaches to reaching these goals, in patients with urinary tract infection (UTI). We describe critical host signaling pathways that define symptoms and pathology and the genetic control of innate immune responses that balance protection against tissue damage. For some of these genes, human relevance has been documented in clinical studies, identifying them as potential targets for immune-modulatory therapies, as a complement to antibiotics.

Association of O-Antigen Serotype with the Magnitude of Initial Systemic Cytokine Responses and Persistence in the Urinary Tract

Urinary tract infection (UTI) is one of the most common ailments requiring both short-term and prophylactic antibiotic therapies. Progression of infection from the bladder to the kidney is associated with more severe clinical symptoms (e.g., fever and vomiting) as well as with dangerous disease sequelae (e.g., renal scaring and sepsis). Host-pathogen interactions that promote bacterial ascent to the kidney are not completely understood. Prior studies indicate that the magnitude of proinflammatory cytokine elicitation in vitro by clinical isolates of uropathogenic Escherichia coli (UPEC) inversely correlates with the severity of clinical disease. Therefore, we hypothesize that the magnitude of initial proinflammatory responses during infection defines the course and severity of disease. Clinical UPEC isolates obtained from patients with a nonfebrile UTI elicited high systemic proinflammatory responses early during experimental UTI in a murine model and were attenuated in bladder and kidney persistence. Conversely, UPEC isolates obtained from patients with febrile UTI elicited low systemic proinflammatory responses early during experimental UTI and exhibited prolonged persistence in the bladder and kidney. Soluble factors in the supernatant from saturated cultures as well as the lipopolysaccharide (LPS) serotype correlated with the magnitude of proinflammatory responses in vitro. Our data suggest that the structure of the O-antigen sugar moiety of the LPS may determine the strength of cytokine induction by epithelial cells. Moreover, the course and severity of disease appear to be the consequence of the magnitude of initial cytokines produced by the bladder epithelium during infection.

IMPORTANCE

The specific host-pathogen interactions that determine the extent and course of disease are not completely understood. Our studies demonstrate that modest changes in the magnitude of cytokine production observed using in vitro models of infection translate into significant ramifications for bacterial persistence and disease severity. While many studies have demonstrated that modifications of the LPS lipid A moiety modulate the extent of Toll-like receptor 4 (TLR4) activation, our studies implicate the O-antigen sugar moiety as another potential rheostat for the modulation of proinflammatory cytokine production.

A Murine Model for Escherichia coli Urinary Tract Infection

Urinary tract infections (UTI) are among the most common bacterial infections of humans. The mouse provides an excellent and tractable model system for cystitis and pyelonephritis caused by Escherichia coli and other uropathogens. Using a well-established model of experimental cystitis in which the bladders of female mice are infected via transurethral catheterization, the molecular details of the pathogenesis of bacterial cystitis have been substantially illuminated in the last decade. Uropathogenic E. coli attach to bladder epithelium (both in human and mouse) via adhesive type 1 pili, establish a replicative niche within epithelial cell cytoplasm, and form intracellular bacterial communities that are protected from antibiotic effects and immune clearance. The use of different inbred and mutant mouse strains offers the opportunity to study outcomes of infection, including resolution, formation of quiescent intracellular bacterial reservoirs, chronic bacterial cystitis, and recurrent infections. Urine, bladder, and kidney tissues can be analyzed by bacterial culture, histology, immunohistochemistry, immunofluorescent and confocal microscopy, electron microscopy, and flow cytometry, while a broad array of soluble markers (e.g., cytokines) can also be profiled in serum, urine, and tissue homogenates by ELISA, Western blotting, multiplex bead array, and other approaches. This model promises to afford continued opportunity for discovery of pathogenic mechanisms and evaluation of therapeutic and preventive strategies for acute, chronic, and recurrent UTI.

Integrated Pathophysiology of Pyelonephritis

Pyelonephritis represents a subset of urinary tract infections that occur from bacteria ascending from the lower to the upper reaches of the genitourinary system, such as the kidney. The renal system contains a range of hydrodynamically and immunologically challenging, interconnected microenvironments where the invading pathogen may populate during the course of the infection. The situation at the infection foci changes dynamically, vacillating between bacterial colonization and clearance, to which the outcome is a summation of all host-pathogen elements in play. A selection of important determinants includes factors of microbial origin, effects of eukaryotic cell signaling, physiological facets of the infected organ, and signals from distal organs. Improved understanding of the multifactorial aspects of molecular pathogenesis of infection requires intravital, cross-disciplinary approaches with high spatio-temporal resolution. The advancement of such approaches promises to eventually provide a comprehensive understanding of the integrated pathophysiology of pyelonephritis.

Genetic Polymorphisms in Inflammasome-Dependent Innate Immunity among Pediatric Patients with Severe Renal Parenchymal Infections

Background

Inflammasome innate immune response activation has been demonstrated in various inflammatory diseases and microbial infections. However, to our knowledge, no study has examined the inflammasome-dependent pathways in patients with urinary tract infection. Defective or variant genes associated with innate immunity are believed to alter the host’s susceptibility to microbial infection. This study investigated genetic polymorphisms in genes encoding inflammasomes and the subsequent released cytokines in pediatric patients with severe renal parenchymal infections.

Methodology

This study included patients diagnosed with acute pyelonephritis (APN) and acute lobar nephronia (ALN) who had no underlying disease or structural anomalies other than vesicoureteral reflux (VUR). Single nucleotide polymorphism (SNP) genotyping was performed in the genes associated with inflammasome formation and activation (NLRP3, CARD8) and subsequent IL–1β cytokine generation (IL–1β).

Principal Findings

A total of 40 SNPs were selected for initial genotyping. Analysis of samples from 48 patients each and 96 controls revealed that only nine SNPs (five SNPs in NLRP3; three SNPs in CARD8; one SNP in IL–1β) had heterozygosity rates >0.01. Hardy–Weinberg equilibrium was satisfied for the observed genotype frequencies of these SNPs. Analysis excluding patients with VUR, a well-known risk factor for severe UTIs, revealed a lower frequency of the CC genotype in NLRP3 (rs4612666) in patients with APN and ALN than in controls. Correction for multiple-SNP testing showed that the non-VUR subgroup of the APN+ALN combined patient groups remained significantly different from the control group (P < 0.0055).

Conclusions

This study is the first to suggest that the inflammasome-dependent innate immunity pathway is associated with the pathogenesis of pediatric severe renal parenchymal infections. Further investigation is warranted to clarify its pathogenic mechanism.

Innate immunity and genetic determinants of urinary tract infection susceptibility

Purpose of review

Urinary tract infections (UTIs) are common, dangerous and interesting. Susceptible individuals experience multiple, often clustered episodes, and in a subset of patients, infections progress to acute pyelonephritis (APN), sometimes accompanied by uro-sepsis. Others develop asymptomatic bacteriuria (ABU). Here, we review the molecular basis for these differences, with the intention to distinguish exaggerated host responses that drive disease from attenuated responses that favour protection and to highlight the genetic basis for these extremes, based on knock-out mice and clinical studies.

Recent findings

The susceptibility to UTI is controlled by specific innate immune signalling and by promoter polymorphisms and transcription factors that modulate the expression of genes controlling these pathways. Gene deletions that disturb innate immune activation either favour asymptomatic bacteriuria or create acute morbidity and disease. Promoter polymorphisms and transcription factor variants affecting those genes are associated with susceptibility in UTI-prone patients.

Summary

It is time to start using genetics in UTI-prone patients, to improve diagnosis and to assess the risk for chronic sequels such as renal malfunction, hypertension, spontaneous abortions, dialysis and transplantation. Furthermore, the majority of UTI patients do not need follow-up, but for lack of molecular markers, they are unnecessarily investigated.

Type 1 Diabetes Prone NOD Mice Have Diminished Cxcr1 mRNA Expression in Polymorphonuclear Neutrophils and CD4+ T Lymphocytes

In humans, CXCR1 and CXCR2 are two homologous proteins that bind ELR+ chemokines. Both receptors play fundamental roles in neutrophil functions such as migration and reactive oxygen species production. Mouse Cxcr1 and Cxcr2 genes are located in an insulin-dependent diabetes genetic susceptibility locus. The non obese diabetic (NOD) mouse is a spontaneous well-described animal model for insulin-dependent type 1 diabetes. In this disease, insulin deficiency results from the destruction of insulin-producing beta cells by autoreactive T lymphocytes. This slow-progressing disease is dependent on both environmental and genetic factors. Here, we report descriptive data about the Cxcr1 gene in NOD mice. We demonstrate decreased expression of mRNA for Cxcr1 in neutrophils and CD4+ lymphocytes isolated from NOD mice compared to other strains, related to reduced NOD Cxcr1 gene promoter activity. Looking for Cxcr1 protein, we next analyze the membrane proteome of murine neutrophils by mass spectrometry. Although Cxcr2 protein is clearly found in murine neutrophils, we did not find evidence of Cxcr1 peptides using this method. Nevertheless, in view of recently-published experimental data obtained in NOD mice, we argue for possible Cxcr1 involvement in type 1 diabetes pathogenesis.

Urinary proteins, vitamin D and genetic polymorphisms as risk factors for febrile urinary tract infection and relation with bacteremia: a case control study

Objective/Purpose

Febrile urinary tract infection (UTI) is a common bacterial disease that may lead to substantial morbidity and mortality especially among the elderly. Little is known about biomarkers that predict a complicated course. Our aim was to determine the role of certain urinary cytokines or antimicrobial proteins, plasma vitamin D level, and genetic variation in host defense of febrile UTI and its relation with bacteremia.

Methods

A case-control study. Out of a cohort of consecutive adults with febrile UTI (n = 787) included in a multi-center observational cohort study, 46 cases with bacteremic E.coli UTI and 45 cases with non-bacteremic E.coli UTI were randomly selected and compared to 46 controls. Urinary IL-6, IL-8, LL37, β-defensin 2 and uromodulin as well as plasma 25-hydroxyvitamin D were measured. In 440 controls and 707 UTI patients polymorphisms were genotyped in the genes CXCR1, DEFA4, DEFB1, IL6, IL8, MYD88, UMOD, TIRAP, TLR1, TLR2, TLR5 and TNF.

Results

IL-6, IL-8, and LL37 are different between controls and UTI patients, although these proteins do not distinguish between patients with and without bacteremia. While uromodulin did not differ between groups, inability to produce uromodulin is more common in patients with bacteremia. Most participants in the study, including the controls, had insufficient vitamin D and, at least in winter, UTI patients have lower vitamin D than controls. Associations were found between the CC genotype of IL6 SNP rs1800795 and occurrence of bacteremia and between TLR5 SNP rs5744168 and protection from UTI. The rare GG genotype of IL6 SNP rs1800795 was associated with higher β-defensin 2 production.

Conclusion

Although no biomarker was able to distinguish between UTI with or without bacteremia, two risk factors for bacteremia were identified. These were inability to produce uromodulin and an IL6 rs1800795 genotype.

Association of interleukin-10 gene promoter polymorphisms with susceptibility to acute pyelonephritis in children

Interleukin-10 (IL-10) is a potent inhibitor of leukocyte chemotaxis, bacterial killing in phagocytes and synthesis of pro-inflammatory cytokines and chemokines, and recent studies have suggested an important role for this immunoregulatory cytokine in the pathogenesis of urinary tract infections (UTIs). Therefore, the gene encoding IL-10 (IL10) is an attractive candidate for association studies attempting to identify susceptibility genes conferring risk of UTIs. In this case-control study, we aimed to investigate the association of single nucleotide polymorphisms (SNPs) in the promoter region of IL10 with acute pyelonephritis in the Slovak population. Polymerase chain reaction with sequence-specific primers was used to analyse IL10 -1082A/G (rs1800896), -819C/T (rs1800871) and -592C/A (rs1800872) SNPs in 147 children with acute pyelonephritis and 215 healthy controls. Comparison of patients with healthy controls using the logistic regression analysis revealed significantly increased risk of developing recurrent attacks of acute pyelonephritis for -1082 G allele in a dominant genetic model GG (GG + AG vs. AA, P = 0.019, odds ratio (OR) = 2.26). A similar tendency was also found when the recurrent acute pyelonephritis subgroup was compared to episodic pyelonephritis cases (GG + AG vs. AA, P = 0.009, OR = 3.38). In conclusion, our results suggest that IL10 -1082 A/G SNP is a susceptibility factor for development of recurrent attacks of acute pyelonephritis.

Streptococcus pneumoniae as a uropathogen in children with urinary tract abnormalities

We describe 3 children with urinary tract abnormalities and large numbers of Streptococcus pneumoniae in their urine, along with a brief review of previously reported cases. These findings strongly suggest that S. pneumoniae is a uropathogen, especially in children with urinary tract abnormalities.

Genetic polymorphisms in Toll-like receptors among pediatric patients with renal parenchymal infections of different clinical severities

Background

Although several studies have suggested single gene defects or variations in the genes associated with host immune response could confer differences in susceptibility to urinary pathogen invasion, no studies have examined the genetic polymorphisms in various toll-like receptors (TLRs) that activate innate immune responses in pediatric renal parenchymal infections of different clinical severities, namely acute pyelonephritis and the clinically more severe disease, acute lobar nephronia.

Methodology

Patients who fulfilled the diagnostic criteria for acute pyelonephritis (APN) and acute lobar nephronia (ALN) without underlying diseases or structural anomalies, except for vesicoureteral reflux (VUR), were enrolled. Genotyping of the single nucleotide polymorphisms (SNPs) in the genes encoding TLR-1, TLR-2, TLR-4, TLR-5, and TLR-6 was performed by matrix-assisted laser desorption/ionization time-of-flight-based mini-sequencing analysis.

Principal Findings

A total of 16 SNPs were selected for genotyping. Analysis of 96 normal and 48 patients’ samples revealed that only four SNPs had heterozygosity rates >0.01. These SNPs were selected for further investigation. Hardy-Weinberg equilibrium was satisfied for the observed genotype frequencies. Statistically significant differences in the genotype frequency of TLR-2 (rs3804100, T1350C) between controls and ALN or (APN+ALN) combined group were identified using the recessive model with the correction for multiple-SNP testing. Further genotype pattern frequency analysis in TLR-2 SNPs (rs3804099 and rs3804100) showed significantly reduced occurrence of the rare allele homozygote (CC+CC) in the no-VUR subgroup of APN and ALN cases.

Conclusions

As the inflammatory responses in ALN patients are more severe than those in APN patients (higher CRP levels, longer duration of fever after antibiotic treatment), these findings suggest that the genetic variant in TLR-2 (rs3804100, T1350C) may protect the host from severe urinary tract infections as ALN.

Susceptibility to acute pyelonephritis or asymptomatic bacteriuria: host-pathogen interaction in urinary tract infections

Our knowledge of the molecular mechanisms of urinary tract infection (UTI) pathogenesis has advanced greatly in recent years. In this review, we provide a general background of UTI pathogenesis, followed by an update on the mechanisms of UTI susceptibility, with a particular focus on genetic variation affecting innate immunity. The innate immune response of the host is critically important in the antibacterial defence mechanisms of the urinary tract, and bacterial clearance normally proceeds without sequelae. However, slight dysfunctions in these mechanisms may result in acute disease and tissue destruction. The symptoms of acute pyelonephritis are caused by the innate immune response, and inflammation in the urinary tract decreases renal tubular function and may give rise to renal scarring, especially in paediatric patients. In contrast, in children with asymptomatic bacteriuria (ABU), bacteria persist without causing symptoms or pathology. Pathogenic agents trigger a response determined by their virulence factors, mediating adherence to the urinary tract mucosa, signalling through Toll-like receptors (TLRs) and activating the defence mechanisms. In ABU strains, such virulence factors are mostly not expressed. However, the influence of the host on UTI severity cannot be overestimated, and rapid progress is being made in clarifying host susceptibility mechanisms. For example, genetic alterations that reduce TLR4 function are associated with ABU, while polymorphisms reducing IRF3 or CXCR1 expression are associated with acute pyelonephritis and an increased risk for renal scarring. It should be plausible to "individualize" diagnosis and therapy by combining information on bacterial virulence and the host response.

Genetic variations of interleukin-8, CXCR1 and CXCR2 genes and risk of acute pyelonephritis in children

Acute pyelonephritis (APN) is the most severe form of urinary tract infection, the etiopathogenesis of which is still not well understood. Previous studies demonstrated that chemotaxis of neutrophils into the tissue and across the infected epithelial layer is a key step in rapid bacterial clearance. Variations within genes encoding the major chemokine interleukin-8 and its receptors CXCR1 and CXCR2 are therefore attractive candidates for participation in genetic predisposition to APN. The aim of our study was to evaluate the association of single nucleotide polymorphisms (SNPs) -251 T/A, +781 C/T, +1633 C/T and +2767 A/T in the IL-8 gene, +2608 G/C in the CXCR1 gene and +1208 C/T in the CXCR2 gene with susceptibility to APN in the Slovak population. PCR-SSP and PCR-RFLP were used to genotype SNPs in 147 children with APN (62 with recurrent and 85 with episodic form) and 215 healthy individuals. Statistical analysis revealed significantly increased frequency of CXCR1 +2608 C allele (P = 0.0238, OR = 2.452, 95% CI = 1.147-5.243) and GC genotype (P = 0.0201, OR = 2.627, 95% CI = 1.188-5.810) and lower frequency of CXCR2 +1208 T allele (P = 0.0408, OR = 0.645, 95% CI = 0.429-0.972) and TT+TC genotypes (P = 0.0497, OR = 0.5273, 95% CI = 0.288-0.964) in patients with recurrent APN compared with healthy controls. Furthermore, the A allele of IL-8 -251 T/A SNP was also significantly overrepresented in patients with recurrent APN when compared with those with only single episode of APN (P = 0.0439, OR = 1.627, 95% CI = 1.019-2.599). Our results indicate that the minor CXCR1 +2608 C allele is associated with significantly increased susceptibility to APN in childhood, while the CXCR2 +1208 T allele confers protection from recurrent APN. Moreover, allele A of the IL-8 -251 T/A may also increase the risk of developing recurrent attacks after the first-time APN.

Genetic control of the variable innate immune response to asymptomatic bacteriuria

The severity of urinary tract infection (UTI) reflects the quality and magnitude of the host response. While strong local and systemic innate immune activation occurs in patients with acute pyelonephritis, the response to asymptomatic bacteriuria (ABU) is low. The immune response repertoire in ABU has not been characterized, due to the inherent problem to distinguish bacterial differences from host-determined variation. In this study, we investigated the host response to ABU and genetic variants affecting innate immune signaling and UTI susceptibility. Patients were subjected to therapeutic urinary tract inoculation with E. coli 83972 to ensure that they were exposed to the same E. coli strain. The innate immune response repertoire was characterized in urine samples, collected from each patient before and after inoculation with bacteria or PBS, if during the placebo arm of the study. Long-term E. coli 83972 ABU was established in 23 participants, who were followed for up to twelve months and the innate immune response was quantified in 233 urine samples. Neutrophil numbers increased in all but two patients and in an extended urine cytokine/chemokine analysis (31 proteins), the chemoattractants IL-8 and GRO-α, RANTES, Eotaxin-1 and MCP-1, the T cell chemoattractant and antibacterial peptide IP-10, inflammatory regulators IL-1-α and sIL-1RA and the T lymphocyte/dendritic cell product sIL-2Rα were detected and variably increased, compared to sterile samples. IL-6, which is associated with symptomatic UTI, remained low and numerous specific immune mediators were not detected. The patients were also genotyped for UTI-associated IRF3 and TLR4 promoter polymorphisms. Patients with ABU associated TLR4 polymorphisms had low neutrophil numbers, IL-6, IP-10, MCP-1 and sIL-2Rα concentrations. Patients with the ABU-associated IRF3 genotype had lower neutrophils, IL-6 and MCP-1 responses than the remaining group. The results suggest that the host-specific, low immune response to ABU mainly includes innate immune mediators and that host genetics directly influence the magnitude of this response.

Acute pyelonephritis and renal scarring are caused by dysfunctional innate immunity in mCxcr2 heterozygous mice

The CXCR1 receptor and chemokine CXCL8 (IL-8) support neutrophil-dependent clearance of uropathogenic Escherichia coli from the urinary tract. CXCR1 is reduced in children prone to pyelonephritis, and heterozygous hCXCR1 polymorphisms are more common in this patient group than in healthy individuals, strongly suggesting a disease association. Since murine CXCR2 (mCXCR2) is functionally similar to human CXCR1, we determined effects of gene heterozygosity on the susceptibility to urinary tract infection by infecting heterozygous (mCxcr2(+/-)) mice with uropathogenic Escherichia coli. Clearance of infection and tissue damage were assessed as a function of innate immunity in comparison to that in knockout (mCxcr2(-/-)) and wild-type (mCxcr2(+/+)) mice. Acute sepsis-associated mortality was increased and bacterial clearance drastically impaired in heterozygous compared to wild-type mice. Chemokine and neutrophil responses were delayed along with evidence of neutrophil retention and unresolved kidney inflammation 1 month after infection. This was accompanied by epithelial proliferation and subepithelial fibrosis. The heterozygous phenotype was intermediate, between knockout and wild-type mice, but specific immune cell infiltrates that accompany chronic infection in knockout mice were not found. Hence, the known heterozygous CXCR1 polymorphisms may predispose patients to acute pyelonephritis and urosepsis.

Genetics of innate immunity and UTI susceptibility

A functional and well-balanced immune response is required to resist most infections. Slight dysfunctions in innate immunity can turn the 'friendly' host defense into an unpleasant foe and give rise to disease. Beneficial and destructive forces of innate immunity have been discovered in the urinary tract and mechanisms by which they influence the severity of urinary tract infections (UTIs) have been elucidated. By modifying specific aspects of the innate immune response to UTI, genetic variation either exaggerates the severity of acute pyelonephritis to include urosepsis and renal scarring or protects against symptomatic disease by suppressing innate immune signaling, as in asymptomatic bacteriuria (ABU). Different genes are polymorphic in patients prone to acute pyelonephritis or ABU, respectively, and yet discussions of UTI susceptibility in clinical practice still focus mainly on social and behavioral factors or dysfunctional voiding. Is it not time for UTIs to enter the era of molecular medicine? Defining why certain individuals are protected from UTI while others have severe, recurrent infections has long been difficult, but progress is now being made, encouraging new approaches to risk assessment and therapy in this large and important patient group, as well as revealing promising facets of 'good' versus 'bad' inflammation.

Urinary tract infections in women: etiology and treatment options

Urinary tract infections (UTI) are common among the female population. It has been calculated that about one-third of adult women have experienced an episode of symptomatic cystitis at least once. It is also common for these episodes to recur. If predisposing factors are not identified and removed, UTI can lead to more serious consequences, in particular kidney damage and renal failure. The aim of this review was to analyze the factors more commonly correlated with UTI in women, and to see what possible solutions are currently used in general practice and specialized areas, as well as those still under investigation. A good understanding of the possible pathogenic factors contributing to the development of UTI and its recurrence will help the general practitioner to interview the patient, search for causes that would otherwise remain undiscovered, and to identify the correct therapeutic strategy.

Genetic polymorphisms and susceptibility to parenchymal renal infection among pediatric patients

BACKGROUND

Patient susceptibility to bacterial urinary tract infections, which is determined by complex pathogen-host interactions, varies between individuals due to genetic variation. The neutrophil-dependent innate immune system is an important part of keeping the urinary tract sterile. This study was performed to explore single nucleotide polymorphisms (SNPs) in genes associated with neutrophil-dependent immunity in pediatric patients with severe parenchymal infections.

METHODS

The subjects included patients who fulfilled the diagnostic criteria of acute pyelonephritis (APN) and acute lobar nephronia (ALN) without underlying disease or structural anomalies (excluding vesicoureteral reflux). Genotyping of the genes encoding toll-like receptor 4 (TLR-4), interleukin-8 (IL-8), and IL-8 receptors CXCR1 and CXCR2 was performed by matrix-assisted laser desorption/ionization time-of-flight-based mini-sequencing analysis.

RESULTS

A total of 17 SNPs, including missense SNPs and those located in promoter regions, were initially selected for genotyping. Only 4 SNPs with a heterozygosity rate >0.01 were evaluated further. The observed genotype frequencies satisfied Hardy-Weinberg equilibrium. Statistical analysis revealed that only IL-8 (rs4073, -251A>T) showed significant differences in genotype and allele frequency between the control and APN or ALN cases. Following the elimination of vesicoureteral reflux, which is a significant risk factor for severe parenchymal infection, a single SNP in IL-8 (rs4073) was found to be associated with clinically severe ALN.

CONCLUSIONS

The AA genotype and A allele of the IL-8 SNP is related to patient susceptibility to parenchymal infection and is correlated with the severity of infection in pediatric APN and ALN patients, probably due to the upregulation of IL-8 expression.

Intracellular lifestyles and immune evasion strategies of uropathogenic Escherichia coli

Paradigms in the pathogenesis of urinary tract infections have shifted dramatically as a result of recent scientific revelations. Beyond extracellular colonization of the bladder luminal surface, as traditional clinical thinking would hold, uropathogenic bacteria direct a complex, intracellular cascade that shelters bacteria from host defenses and leads to persistent bacterial residence within the epithelium. After epithelial invasion, many organisms are promptly expelled by bladder epithelial cells; a minority establish a niche in the cytoplasm that results in the development of biofilm-like intracellular bacterial communities and serves as the primary location for bacterial expansion. Exfoliation of the superficial epithelial layer acts to reduce the bacterial load but facilitates chronic residence of small nests of bacteria that later reemerge to cause some episodes of recurrent cystitis, a familiar clinical scenario in otherwise healthy women. Advances in both in vitro and animal models of cystitis promise to provide insights into the bacterial and host transcriptional and biochemical pathways that define these pathogenic stages.

Association of Toll-like receptor 4 gene polymorphism and expression with urinary tract infection types in adults

BACKGROUND

Innate immunity of which Toll-like receptor (TLR) 4 and CXCR1 are key elements plays a central role in the development of urinary tract infection (UTI). Although the relation between the genetics of TLR4 and CXCR1 and UTI is investigated partly, the polymorphisms and expression of TLR4 and CXCR1 in different types of UTI in adults are not extremely clear.

METHODOLOGY/PRINCIPAL FINDINGS

This study investigates the presence of TLR4 A (896) G and CXCR1 G (2608) C polymorphisms in 129 UTI patients using RFLP-PCR. Gene and allelic prevalence were compared with 248 healthy controls. Flow cytometry was used to detect TLR4 and CXCR1 expression in the monocytes of UTI patients and healthy controls. TLR4 (896) AG genotype and TLR4 (896) G allele had higher prevalence in UTI (especially in acute cystitis and urethritis) patients, whereas CXCR1 (2608) GC genotype and CXCR1 (2608) C allele had lower prevalence in UTI patients than controls. TLR4 expression was significantly lower in chronic UTI patients than in acute pyelonephritis or healthy controls. CXCR1 expression was similar in both controls and patients. TLR4 expression in chronic UTI patients after astragalus treatment was higher than pre-treatment.

CONCLUSIONS

The results indicate the relationship between the carrier status of TLR4 (896) G alleles and the development of UTI, especially acute cystitis and urethritis, in adults. TLR4 expression levels are correlated with chronic UTI.

The IL-6 -174G/C polymorphism and renal scarring in children with first acute pyelonephritis

Urinary tract infections (UTI) are common in infants and children and may result in serious complications, such as renal scarring, hypertension, and renal failure. Identification of the new markers in relation to acute pyelonephritis (APN) and its treatment is essential for designing interventions that would minimize tissue damage. This prospective study investigated the first UTI infection in 71 children (age range: 1-24 months) in respect to interleukin-6 (IL-6) -174G/C polymorphism and renal scarring. The patients were divided into an APN group and a lower UTI group according to dimercaptosuccinic acid (DMSA). The IL-6 -174G/C genotypes were determined by tetra-primer ARMSPCR. Serum IL-6 was significantly higher in the APN group than in the group with lower UTI (p<0.05). In both groups, the -174G/C genotype and allele frequencies did not differ significantly from the control group. The highest white blood cell (WBC) count was observed in the CC genotype (p<0.05). A non-significant trend toward higher serum IL-6 was observed in children with CC genotype. On follow-up DMSA imaging performed 6 months later, renal scarring was detected in 36.9% of APN children. We did not find the significant association of IL-6 -174G/C polymorphism with APN and/or postinfectious renal scarring. These results indicate that serum IL-6 concentrations were significantly higher in children with APN than in patients with lower UTI.

Pathogen specific, IRF3-dependent signaling and innate resistance to human kidney infection

The mucosal immune system identifies and fights invading pathogens, while allowing non-pathogenic organisms to persist. Mechanisms of pathogen/non-pathogen discrimination are poorly understood, as is the contribution of human genetic variation in disease susceptibility. We describe here a new, IRF3-dependent signaling pathway that is critical for distinguishing pathogens from normal flora at the mucosal barrier. Following uropathogenic E. coli infection, Irf3(-/-) mice showed a pathogen-specific increase in acute mortality, bacterial burden, abscess formation and renal damage compared to wild type mice. TLR4 signaling was initiated after ceramide release from glycosphingolipid receptors, through TRAM, CREB, Fos and Jun phosphorylation and p38 MAPK-dependent mechanisms, resulting in nuclear translocation of IRF3 and activation of IRF3/IFNβ-dependent antibacterial effector mechanisms. This TLR4/IRF3 pathway of pathogen discrimination was activated by ceramide and by P-fimbriated E. coli, which use ceramide-anchored glycosphingolipid receptors. Relevance of this pathway for human disease was supported by polymorphic IRF3 promoter sequences, differing between children with severe, symptomatic kidney infection and children who were asymptomatic bacterial carriers. IRF3 promoter activity was reduced by the disease-associated genotype, consistent with the pathology in Irf3(-/-) mice. Host susceptibility to common infections like UTI may thus be strongly influenced by single gene modifications affecting the innate immune response.

Inhibition of TIR domain signaling by TcpC: MyD88-dependent and independent effects on Escherichia coli virulence

Toll-like receptor signaling requires functional Toll/interleukin-1 (IL-1) receptor (TIR) domains to activate innate immunity. By producing TIR homologous proteins, microbes inhibit host response induction and improve their own survival. The TIR homologous protein TcpC was recently identified as a virulence factor in uropathogenic Escherichia coli (E. coli), suppressing innate immunity by binding to MyD88. This study examined how the host MyD88 genotype modifies the in vivo effects of TcpC and whether additional, TIR-domain containing proteins might be targeted by TcpC. In wild type mice (wt), TcpC enhanced bacterial virulence, increased acute mortality, bacterial persistence and tissue damage after infection with E. coli CFT073 (TcpC+), compared to a ΔTcpC deletion mutant. These effects were attenuated in Myd88(-/-) and Tlr4(-/-) mice. Transcriptomic analysis confirmed that TcpC inhibits MYD88 dependent gene expression in CFT073 infected human uroepithelial cells but in addition the inhibitory effect included targets in the TRIF and IL-6/IL-1 signaling pathways, where MYD88 dependent and independent signaling may converge. The effects of TcpC on bacterial persistence were attenuated in Trif (-/-) or Il-1β (-/-) mice and innate immune responses to ΔTcpC were increased, confirming that Trif and Il-1β dependent targets might be involved in vivo, in addition to Myd88. Furthermore, soluble TcpC inhibited Myd88 and Trif dependent TLR signaling in murine macrophages. Our results suggest that TcpC may promote UTI-associated pathology broadly, through inhibition of TIR domain signaling and downstream pathways. Dysregulation of the host response by microbial TcpC thus appears to impair the protective effects of innate immunity, while promoting inflammation and tissue damage.

Host imprints on bacterial genomes--rapid, divergent evolution in individual patients

Bacteria lose or gain genetic material and through selection, new variants become fixed in the population. Here we provide the first, genome-wide example of a single bacterial strain's evolution in different deliberately colonized patients and the surprising insight that hosts appear to personalize their microflora. By first obtaining the complete genome sequence of the prototype asymptomatic bacteriuria strain E. coli 83972 and then resequencing its descendants after therapeutic bladder colonization of different patients, we identified 34 mutations, which affected metabolic and virulence-related genes. Further transcriptome and proteome analysis proved that these genome changes altered bacterial gene expression resulting in unique adaptation patterns in each patient. Our results provide evidence that, in addition to stochastic events, adaptive bacterial evolution is driven by individual host environments. Ongoing loss of gene function supports the hypothesis that evolution towards commensalism rather than virulence is favored during asymptomatic bladder colonization.

Polymorphisms in the surfactant protein a gene are associated with the susceptibility to recurrent urinary tract infection in chinese women

Some risk factors for susceptibility to recurrent urinary tract infection (r-UTI) are well known, but the genetic role in acquiring the disease is poorly understood. Surfactant protein A and D (SP-A and SP-D) play an important role in modulation of lung inflammatory processes. The SP-A1 and SP-A2 genes encoding SP-A and the SP-D gene are highly polymorphic, and some of polymorphisms are associated with several infective diseases, including pyelonephritis. In the present study, we investigated whether some of these polymorphisms are associated with the risk of r-UTI in Chinese population. Genomic DNA was extracted from blood samples of 32 female patients with r-UTI and 30 age-matched, unrelated healthy female subjects. Genotyping of gene polymorphisms was analyzed by PCR. Among 11 single nucleotide polymorphisms (SNPs) (five of SP-A1, four of SP-A2 and two of SP-D) observed in the enrolled subjects, Ala19Val of SP-A1 and Lys223Gln of SP-A2 were associated with susceptibility to r-UTI. The frequencies of 19Ala allele of SP-A1 gene (p = 0.038) and 223Gln allele of SP-A2 gene (p = 0.012) in the patients were significantly higher than those in healthy subjects. The serum SP-A and SP-D levels were increased and the urine SP-A and SP-D levels were decreased in r-UTI patients compared with control subjects (p < 0.05). r-UTI patients with 19Ala/Ala or 223Gln/Gln genotype were associated with high serum and low urine SP-A levels (p < 0.01). Therefore, the 19Ala allele of SP-A1 gene and the 223Gln allele of SP-A2 gene are risk factors for r-UTI.