Uropathogenic Escherichia coli P and Type 1 fimbriae act in synergy in a living host to facilitate renal colonization leading to nephron obstruction

Tiny but Mighty: Small RNAs-The Micromanagers of Bacterial Survival, Virulence, and Host-Pathogen Interactions

Bacterial pathogens have evolved diverse strategies to infect hosts, evade immune responses, and establish successful infections. While the role of transcription factors in bacterial virulence is well documented, emerging evidence highlights the significant contribution of small regulatory RNAs (sRNAs) in bacterial pathogenesis. These sRNAs function as posttranscriptional regulators that fine-tune gene expression, enabling bacteria to adapt rapidly to challenging environments. This review explores the multifaceted roles of bacterial sRNAs in host-pathogen interactions. Firstly, it examines how sRNAs regulate pathogenicity by modulating the expression of key virulence factors, including fimbriae, toxins, and secretion systems, followed by discussing the role of sRNAs in bacterial stress response mechanisms that counteract host immune defenses, such as oxidative and envelope stress. Additionally, this review investigates the involvement of sRNAs in antibiotic resistance by regulating efflux pumps, biofilm formation, and membrane modifications, which contribute to multi-drug resistance phenotypes. Lastly, this review highlights how sRNAs contribute to intra- and interspecies communication through quorum sensing, thereby coordinating bacterial behavior in response to environmental cues. Understanding these regulatory networks governed by sRNAs is essential for the development of innovative antimicrobial strategies. This review highlights the growing significance of sRNAs in bacterial pathogenicity and explores their potential as therapeutic targets for the treatment of bacterial infections.

Phage Endolysins as Promising and Effective Candidates for Use Against Uropathogenic Escherichia coli

The presented in silico and phylogenetic analysis of putative endolysins potentially produced by phages infecting uropathogenic Escherichia coli (UPEC) demonstrates their remarkable diversity. These proteins exhibit significant variations in sequence length, molecular weight, isoelectric point, and stability, as well as diverse functional domains determining their enzymatic activity, including lysin, lysozyme, hydrolase, amidase, and peptidase functions. Due to their predicted lytic properties, endolysins hold great promise in combating UPEC bacteria, including those within biofilms, which are often highly resistant to conventional treatments. Despite their potential, several challenges hinder the full utilization of endolysins. These include the relatively small number of identified proteins, challenges in the annotation process, and the scarcity of studies evaluating their efficacy in vitro and in vivo against Gram-negative bacteria. In this work, we emphasize these challenges while also underlining the potential of endolysins as an effective tool against UPEC infections. Their effectiveness could be significantly enhanced when combined with agents that disrupt the outer membrane of these bacteria, making them a promising alternative or complement to existing antimicrobial strategies. Further research is necessary to fully explore their therapeutic potential.

Bacterial adhesion strategies and countermeasures in urinary tract infection

Urinary tract infections (UTIs) are compounded by antimicrobial resistance, which increases the risk of UTI recurrence and antibiotic treatment failure. This also intensifies the burden of disease upon healthcare systems worldwide, and of morbidity and mortality. Uropathogen adhesion is a critical step in the pathogenic process, as has been mainly shown for Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Streptococcus agalactiae, Proteus, Enterococcus and Staphylococcus species. Although many bacterial adhesion molecules from these uropathogens have been described, our understanding of their contributions to UTIs is limited. Here we explore knowledge gaps in the UTI field, as we discuss the broader repertoire of uropathogen adhesins, including their role beyond initial attachment and the counter-responses of the host immune system. Finally, we describe the development of therapeutic approaches that target uropathogenic adhesion strategies and provide potential alternatives to antibiotics.

The maturation of native uropathogenic Escherichia coli biofilms seen through a non-interventional lens

Urinary tract infections (UTI) caused by uropathogenic Escherichia coli (UPEC) are a significant global health challenge. The UPEC biofilm lifestyle is believed to play an important role in infection recurrency and treatment resistance, but our understanding of how the extracellular matrix (ECM) components curli and cellulose contribute to biofilm formation and pathogenicity is limited. Here, we study the spatial and temporal development of native UPEC biofilm using agar-based detection methods where the non-toxic, optically active fluorescent tracer EbbaBiolight 680 reports the expression and structural location of curli in real-time. An in vitro screen of the biofilm capacity of common UPEC strains reveals significant strain variability and identifies UPEC No. 12 (UPEC12) as a strong biofilm former at 28 °C and 37 °C. Non-interventional microscopy, including time-lapse and 2-photon, reveal significant horizontal and vertical heterogeneity in the UPEC12 biofilm structure. We identify region-specific expression of curli, with a shift in localization from the bottom of the flat central regions of the biofilm to the upper surface in the topographically dramatic intermediate region. When investigating if the rdar morphotype affects wettability of the biofilm surface, we found that the nano-architecture of curli guided by cellulose, rather than the rdar macrostructures, leads to increased hydrophobicity of the biofilm. By providing new insights at exceptional temporal and spatial resolution, we demonstrate how non-interventional analysis of native biofilms will facilitate the next generation of understanding into the roles of ECM components during growth of UPEC biofilms and their contribution to the pathogenesis of UTI.

A comprehensive in silico analysis of putative outer membrane and secretory hydrolases from the pathogenic Leptospira: Possible implications in pathogenesis

Outer surface/membrane and virulent secretory proteins are primarily crucial for pathogenesis. Secreted and outer membrane hydrolases of many pathogens play an important role in attenuating the host immune system. Leptospira expresses many such proteins, and few have been characterized to display various roles, including host immune evasion. However, identification, classification, characterization, and elucidation of the possible role of Leptospira's outer membrane and secretory hydrolases have yet to be explored. In the present study, we used bioinformatics tools to predict exported proteins from the pathogenic Leptospira proteome. Moreover, we focused on secretory and outer membrane putative hydrolases from the exported proteins to generate a deeper understanding. Our analysis yielded four putative outer/secretory hydrolases, LIC_10995, LIC_11183, LIC_11463, and LIC_12988, containing α/β hydrolase fold and displayed similarity with lipase motif. Moreover, their conservation analysis of the predicted hydrolases across the spectrum of different Leptospira species showed high clustering with the pathogenic species. Outer membrane and secretory proteins with lipolytic activity may have a role in pathogenesis. This is the first bioinformatics analysis of secretory and outer membrane α/β hydrolases from leptospiral species. However, experimental studies are indeed required to unravel this possibility.

Distribution of papA and papG Variants among Escherichia coli Genotypes: Association with Major Extraintestinal Pathogenic Lineages

The pyelonephritis-associated fimbria (P fimbria) is one of the most recognized adhesion determinants of extraintestinal pathogenic Escherichia coli strains (ExPECs). Twelve variants have been described for the gene encoding the P fimbria major structural subunit PapA and three variants for the gene encoding the adhesin subunit PapG. However, their distribution among the ExPEC diversity has not been comprehensively addressed. A complete landscape of that distribution might be valuable for delineating basic studies about the pathogenicity mechanisms of ExPECs and following up on the evolution of ExPEC lineages, particularly those most epidemiologically relevant. Therefore, we performed a massive descriptive study to detect the papA and papG variants along different E. coli genotypes represented by genomic sequences contained in the NCBI Assembly Refseq database. The most common papA variants were F11, F10, F48, F16, F12, and F7-2, which were found in significant association with the most relevant ExPEC genotypes, the phylogroups B2 and D, and the sequence types ST95, ST131, ST127, ST69, ST12, and ST73. On the other hand, the papGII variant was by far the most common followed by papGIII, and both were also found to have a significant association with common ExPEC genotypes. We noticed the presence of genomes, mainly belonging to the sequence type ST12, harboring two or three papA variants and two papG variants. Furthermore, the most common papA and papG variants were also detected in records representing strains isolated from humans and animals such as poultry, bovine, and dogs, supporting previous hypotheses of potential cross-transmission. Finally, we characterized a set of 17 genomes from Chilean uropathogenic E. coli strains and found that ST12 and ST73 were the predominant sequence types. Variants F7-1, F7-2, F8, F9, F11, F13, F14, F16, and F48 were detected for papA, and papGII and papGIII variants were detected for papG. Significant associations with the sequence types observed in the analysis of genomes contained in the NCBI Assembly Refseq database were also found in this collection in 16 of 19 cases for papA variants and 7 of 9 cases for the papG variants. This comprehensive characterization might support future basic studies about P fimbria-mediated ExPEC adherence and future typing or epidemiological studies to monitor the evolution of ExPECs producing P fimbria.

Differences in P-Type and Type 1 Uropathogenic Escherichia coli Urinary Anti-Adhesion Activity of Cranberry Fruit Juice Dry Extract Product and D-Mannose Dietary Supplement

BACKGROUND

Urinary tract infection (UTI) prevention benefits of cranberry intake are clinically validated, especially for women and children. To ensure the benefits of cranberry dietary supplement products, the anti-adhesion activity (AAA) against uropathogenic bacteria is routinely used in in vitro bioassays to determine the activity in whole product formulations, isolated compounds, and ex vivo bioassays to assess urinary activity following intake. D-mannose is another dietary supplement taken for UTI prevention, based on the anti-adhesion mechanism.

OBJECTIVE

Compare the relative AAA of cranberry and D-mannose dietary supplements against the most important bacterial types contributing to the pathogenesis of UTI, and consider how certain components potentially induce in vivo activity.

METHODS

The current study used a crossover design to determine ex vivo AAA against both P- and Type 1-fimbriated uropathogenic Escherichia coli of either D-mannose or a cranberry fruit juice dry extract product containing 36 mg of soluble proanthocyanidins (PACs), using bioassays that measure urinary activity following consumption. AAA of extracted cranberry compound fractions and D-mannose were compared in vitro and potential induction mechanisms of urinary AAA explored.

RESULTS

The cranberry dietary supplement exhibited both P-type and Type 1 in vitro and ex vivo AAA, while D-mannose only prevented Type 1 adhesion. Cranberry also demonstrated more robust and consistent ex vivo urinary AAA than D-mannose over each 1-week study period at different urine collection time points. The means by which the compounds with in vitro activity in each supplement product could potentially induce the AAA in urines was discussed relative to the data.

CONCLUSIONS

Results of the current study provide consumers and healthcare professionals with additional details on the compounds and mechanisms involved in the positive, broad-spectrum AAA of cranberry against both E. coli bacterial types most important in UTIs and uncovers limitations on AAA and effectiveness of D-mannose compared to cranberry.

The biological function of the type II toxin-antitoxin system ccdAB in recurrent urinary tract infections

Urinary tract infections (UTIs) represent a significant challenge in clinical practice, with recurrent forms (rUTIs) posing a continual threat to patient health. Escherichia coli (E. coli) is the primary culprit in a vast majority of UTIs, both community-acquired and hospital-acquired, underscoring its clinical importance. Among different mediators of pathogenesis, toxin-antitoxin (TA) systems are emerging as the most prominent. The type II TA system, prevalent in prokaryotes, emerges as a critical player in stress response, biofilm formation, and cell dormancy. ccdAB, the first identified type II TA module, is renowned for maintaining plasmid stability. This paper aims to unravel the physiological role of the ccdAB in rUTIs caused by E. coli, delving into bacterial characteristics crucial for understanding and managing this disease. We investigated UPEC-induced rUTIs, examining changes in type II TA distribution and number, phylogenetic distribution, and Multi-Locus Sequence Typing (MLST) using polymerase chain reaction (PCR). Furthermore, our findings revealed that the induction of ccdB expression in E. coli BL21 (DE3) inhibited bacterial growth, observed that the expression of both ccdAB and ccdB in E. coli BL21 (DE3) led to an increase in biofilm formation, and confirmed that ccdAB plays a role in the development of persistent bacteria in urinary tract infections. Our findings could pave the way for novel therapeutic approaches targeting these systems, potentially reducing the prevalence of rUTIs. Through this investigation, we hope to contribute significantly to the global effort to combat the persistent challenge of rUTIs.

Uropathogenic Escherichia coli causes significant urothelial damage in an ex vivo porcine bladder model, with no protective effect observed from cranberry or d-mannose

Urinary tract infections (UTIs), primarily caused by uropathogenic Escherichia coli (UPEC), have an unclear impact on bladder mucosal physiology. This study investigates UPEC's effects on the urothelium and lamina propria using an ex vivo porcine bladder model. Bladder mucosal strips were analysed for contractile responses to acetylcholine, serotonin, and neurokinin A. Given rising antibiotic resistance, non-antibiotic agents such as cranberry and d-mannose were also evaluated for their potential to prevent UPEC-induced damage. The findings of the current study revealed that UPEC significantly compromised urothelial integrity, barrier function, and permeability, with loss of urothelial cells, uroplakins, and tight junction protein ZO-1 expression. Additionally, infected bladders exhibited a markedly enhanced contractile response to serotonin compared to uninfected controls. Notably, neither cranberry nor d-mannose offered protection against UPEC-mediated damage or mitigated the heightened serotonin-induced contractility. This study provides novel insights into how UPEC disrupts bladder cell biology and highlights the possible involvement of serotonin in the pathophysiology of UTIs.

Lower Urinary Tract Inflammation and Infection: Key Microbiological and Immunological Aspects

The urinary system, primarily responsible for the filtration of blood and waste, is affected by several infectious and inflammatory conditions. Focusing on the lower tract, this review outlines the physiological and immune landscape of the urethra and bladder, addressing key immunological and microbiological aspects of important infectious/inflammatory conditions. The conditions addressed include urethritis, interstitial cystitis/bladder pain syndrome, urinary tract infections, and urosepsis. Key aspects of each condition are addressed, including epidemiology, pathophysiology, and clinical considerations. Finally, therapeutic options are outlined, highlighting gaps in the knowledge and novel therapeutic approaches.

Uropathogenic Escherichia coli (UPEC)-Associated Urinary Tract Infections: The Molecular Basis for Challenges to Effective Treatment

Urinary tract infections (UTIs) are among the most common bacterial infections, especially among women and older adults, leading to a significant global healthcare cost burden. Uropathogenic Escherichia coli (UPEC) are the most common cause and accounts for the majority of community-acquired UTIs. Infection by UPEC can cause discomfort, polyuria, and fever. More serious clinical consequences can result in urosepsis, kidney damage, and death. UPEC is a highly adaptive pathogen which presents significant treatment challenges rooted in a complex interplay of molecular factors that allow UPEC to evade host defences, persist within the urinary tract, and resist antibiotic therapy. This review discusses these factors, which include the key genes responsible for adhesion, toxin production, and iron acquisition. Additionally, it addresses antibiotic resistance mechanisms, including chromosomal gene mutations, antibiotic deactivating enzymes, drug efflux, and the role of mobile genetic elements in their dissemination. Furthermore, we provide a forward-looking analysis of emerging alternative therapies, such as phage therapy, nano-formulations, and interventions based on nanomaterials, as well as vaccines and strategies for immunomodulation. This review underscores the continued need for research into the molecular basis of pathogenesis and antimicrobial resistance in the treatment of UPEC, as well as the need for clinically guided treatment of UTIs, particularly in light of the rapid spread of multidrug resistance.

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.

FimH and Type 1 Pili Mediated Tumor Cell Cytotoxicity by Uropathogenic Escherichia coli In Vitro

Uropathogenic Escherichia coli express hairlike proteinaceous surface projections, known as chaperone-usher pathway (CUP) pili. Type 1 pili are CUP pili with well-established pathogenic properties. The FimH adhesin subunit of type 1 pili plays a key role in the pathogenesis of urinary tract infections (UTIs) as it mediates the adhesion of the bacteria to urothelial cells of the bladder. In this study, two breast cancer cell lines, MDA-MB-231 and MCF-7, were used to demonstrate the cytotoxic activities of type 1 piliated uropathogenic E. coli UTI89 on breast cancer cells in a type 1 pili and FimH-mediated manner. E. coli were grown in static and shaking conditions to induce or inhibit optimal type 1 pili biogenesis, respectively. Deletion constructs of UTI89 ΔfimH and a complemented strain (UTI89 ΔfimH/pfimH) were further utilized to genetically assess the effect of type 1 pili and FimH on cancer cell viability. After incubation with the different strains, cytotoxicity was measured using trypan blue exclusion assays. UTI89 grown statically caused significant cytotoxicity in both breast cancer cell lines whereas cytotoxicity was reduced when the cells were incubated with bacteria grown under shaking conditions. The incubation of both MDA-MB-231 and MCF-7 with UTI89 Δfim operon or ΔfimH showed a significant reduction in cytotoxicity exerted by the bacterial strains, revealing that type 1 pili expression was necessary for cytotoxicity. Complementing the ΔfimH strain with pfimH reversed the phenotype, leading to a significant increase in cytotoxicity. Incubating type 1 pili expressing bacteria with the competitive FimH inhibitor D-mannose before cancer cell treatment also led to a significant reduction in cytotoxicity on both MDA-MB-231 and MCF-7 cancer cells, compared to vehicle control or D-mannose alone, indicating the requirement for functional FimH for cytotoxicity. Overall, our results reveal that, as opposed to UTI89 lacking type 1 pili, type 1 piliated UTI89 causes significant cancer cell mortality in a FimH-mediated manner, that is decreased with D-mannose.

Dynamic single cell analysis in a proximal-tubule-on-chip reveals heterogeneous epithelial colonization strategies of uropathogenic Escherichia coli under shear stress

The urinary tract is a hydrodynamically challenging microenvironment and uropathogenic Escherichia coli (UPEC) must overcome several physiological challenges in order to adhere and establish a urinary tract infection. Our previous work in vivo revealed a synergy between different UPEC adhesion organelles, which facilitated effective colonization of the renal proximal tubule. To allow high-resolution real-time analysis of this colonization behavior, we established a biomimetic proximal-tubule-on-chip (PToC). The PToC allowed for single-cell resolution analysis of the first stages of bacterial interaction with host epithelial cells, under physiological flow. Time-lapse microscopy and single-cell trajectory analysis in the PToC revealed that while the majority of UPEC moved directly through the system, a minority population initiated heterogeneous adhesion, identified as either rolling or bound. Adhesion was predominantly transient and mediated by P pili at the earliest time-points. These bound bacteria initiated a founder population which rapidly divided, leading to 3D microcolonies. Within the first hours, the microcolonies did not express extracellular curli matrix, but rather were dependent on Type 1 fimbriae as the key element in the microcolony structure. Collectively, our results show the application of Organ-on-chip technology to address bacterial adhesion behaviors, demonstrating a well-orchestrated interplay and redundancy between adhesion organelles that enables UPEC to form microcolonies and persist under physiological shear stress.

A high-throughput sequencing approach identifies immunotherapeutic targets for bacterial meningitis in neonates

BACKGROUND

Worldwide, Escherichia coli is the leading cause of neonatal Gram-negative bacterial meningitis, but full understanding of the pathogenesis of this disease is not yet achieved. Moreover, to date, no vaccine is available against bacterial neonatal meningitis.

METHODS

Here, we used Transposon Sequencing of saturated banks of mutants (TnSeq) to evaluate E. coli K1 genetic fitness in murine neonatal meningitis. We identified E. coli K1 genes encoding for factors important for systemic dissemination and brain infection, and focused on products with a likely outer-membrane or extra-cellular localization, as these are potential vaccine candidates. We used in vitro and in vivo models to study the efficacy of active and passive immunization.

RESULTS

We selected for further study the conserved surface polysaccharide Poly-β-(1-6)-N-Acetyl Glucosamine (PNAG), as a strong candidate for vaccine development. We found that PNAG was a virulence factor in our animal model. We showed that both passive and active immunization successfully prevented and/or treated meningitis caused by E. coli K1 in neonatal mice. We found an excellent opsonophagocytic killing activity of the antibodies to PNAG and in vitro these antibodies were also able to decrease binding, invasion and crossing of E. coli K1 through two blood brain barrier cell lines. Finally, to reinforce the potential of PNAG as a vaccine candidate in bacterial neonatal meningitis, we demonstrated that Group B Streptococcus, the main cause of neonatal meningitis in developed countries, also produced PNAG and that antibodies to PNAG could protect in vitro and in vivo against this major neonatal pathogen.

INTERPRETATION

Altogether, these results indicate the utility of a high-throughput DNA sequencing method to identify potential immunotherapy targets for a pathogen, including in this study a potential broad-spectrum target for prevention of neonatal bacterial infections.

FUNDINGS

ANR Seq-N-Vaq, Charles Hood Foundation, Hearst Foundation, and Groupe Pasteur Mutualité.

Biofilm Lifestyle in Recurrent Urinary Tract Infections

Urinary tract infections (UTIs) represent one of the most common infections that are frequently encountered in health care facilities. One of the main mechanisms used by bacteria that allows them to survive hostile environments is biofilm formation. Biofilms are closed bacterial communities that offer protection and safe hiding, allowing bacteria to evade host defenses and hide from the reach of antibiotics. Inside biofilm communities, bacteria show an increased rate of horizontal gene transfer and exchange of resistance and virulence genes. Additionally, bacterial communication within the biofilm allows them to orchestrate the expression of virulence genes, which further cements the infestation and increases the invasiveness of the infection. These facts stress the necessity of continuously updating our information and understanding of the etiology, pathogenesis, and eradication methods of this growing public health concern. This review seeks to understand the role of biofilm formation in recurrent urinary tact infections by outlining the mechanisms underlying biofilm formation in different uropathogens, in addition to shedding light on some biofilm eradication strategies.

Virulence factors of uropathogens and their role in host pathogen interactions

Gram-positive and Gram-negative bacterial pathogens are commonly found in Urinary Tract Infection (UTI), particularly infected in females like pregnant women, elder people, sexually active, or individuals prone to other risk factors for UTI. In this article, we review the expression of virulence surface proteins and their interaction with host cells for the most frequently isolated uropathogens: Escherichia coli, Enterococcus faecalis, Proteus mirabilis, Klebsiella pneumoniae, and Staphylococcus saprophyticus. In addition to the host cell interaction, surface protein regulation was also discussed in this article. The surface protein regulation serves as a key tool in differentiating the pathogen isotypes. Furthermore, it might provide insights on novel diagnostic methods to detect uropathogen that are otherwise easily overlooked due to limited culture-based assays. In essence, this review shall provide an in-depth understanding on secretion of virulence factors of various uropathogens and their role in host-pathogen interaction, this knowledge might be useful in the development of therapeutics against uropathogens.

Role of aggregate-forming pilus (AFP) in adherence and colonization of both intestinal and urinary tracts

Hybrid-pathogenic Escherichia coli represent an important group of strains associated with intestinal and extraintestinal infections. Recently, we described strain UPEC-46, a uropathogenic/enteroaggregative E. coli (UPEC/EAEC) strain presenting the aggregative adherence (AA) pattern on bladder and colorectal epithelial cells mediated by aggregate-forming pili (AFP). However, the role of AFP and other uninvestigated putative fimbriae operons in UPEC-46 pathogenesis remains unclear. Thus, this study evaluated the involvement of AFP and other adhesins in uropathogenicity and intestinal colonization using different in vitro and in vivo models. The strain UPEC-46 was able to adhere and invade intestinal and urinary cell lines. A library of transposon mutants also identified the involvement of type I fimbriae (TIF) in the adherence to HeLa cells, in addition to colorectal and bladder cell lines. The streptomycin-treated mouse in vivo model also showed an increased number of bacterial counts in the colon in the presence of AFP and TIF. In the mouse model of ascending urinary tract infection (UTI), AFP was more associated with kidney colonization, while TIF appears to mediate bladder colonization. Results observed in in vivo experiments were also confirmed by electron microscopy (EM) analyses. In summary, the in vitro and in vivo analyses show a synergistic role of AFP and TIF in the adherence and colonization of intestinal and urinary epithelia. Therefore, we propose that hybrid E. coli strains carrying AFP and TIF could potentially cause intestinal and urinary tract infections in the same patient.

Distribution of papG alleles among uropathogenic Escherichia coli from reproductive age women

BACKGROUND

Extraintestinal Escherichia coli (E. coli) causing urinary tract infections (UTIs), and often referred to as uropathogenic E. coli (UPEC), are a major contributor to the morbidity of UTIs and associated healthcare costs. UPEC possess several virulence factors (VFs) for infecting and injuring the host. We studied the papG allele distribution, and its association with other VF genes and phylogenetic groups, amongst 836 UPEC and fecal isolates from reproductive age women.

RESULTS

The papGII gene was highly prevalent amongst pyelonephritis isolates (68%), whilst the majority, albeit smaller proportion, of cystitis isolates (31%) harboured the papGIII gene. Among the pyelonephritis and cystitis isolates, papG positive isolates on average had higher VF gene scores, and were more likely to belong to phylogenetic group B2, than their negative counterparts. This was mostly due to the contribution of papGII isolates, which on average contained more VF genes than their papGIII counterparts, irrespective of the uro-clinical syndrome. However, the papGII isolates from the pyelonephritis cohort had higher VF gene scores than the cystitis ones, suggesting presence of possible papGII clones with differing inferred virulence potential. Furthermore, papGII isolates were more likely to possess an intact pap gene operon than their papGIII counterparts. Also of note was the high proportion of isolates with the papGI allele which was not associated with other pap operon genes; and this finding has not been described before.

CONCLUSIONS

The association of the papGII gene with several VF genes compared to the papGIII gene, appears to explain the abundance of these genes in pyelonephritis and cystitis isolates, respectively.

Intravital Multiphoton Microscopy as a Tool for Studying Renal Physiology, Pathophysiology and Therapeutics

Intravital multiphoton microscopy has empowered investigators to study dynamic cell and subcellular processes in vivo within normal and disease organs. Advances in hardware, software, optics, transgenics and fluorescent probe design and development have enabled new quantitative approaches to create a disruptive technology pioneering advances in understanding of normal biology, disease pathophysiology and therapies. Offering superior spatial and temporal resolution with high sensitivity, investigators can follow multiple processes simultaneously and observe complex interactions between different cell types, intracellular organelles, proteins and track molecules for cellular uptake, intracellular trafficking, and metabolism in a cell specific fashion. The technique has been utilized in the kidney to quantify multiple dynamic processes including capillary flow, permeability, glomerular function, proximal tubule processes and determine the effects of diseases and therapeutic mechanisms. Limitations include the depth of tissue penetration with loss of sensitivity and resolution due to scattered emitted light. Tissue clearing technology has virtually eliminated penetration issues for fixed tissue studies. Use of multiphoton microscopy in preclinical animal models offers distinct advantages resulting in new insights into physiologic processes and the pathophysiology and treatment of diseases.

Phylogenicity and Virulence Profiles of Clinical Escherichia coli Isolates in the Ho Teaching Hospital of Ghana

Background. Escherichia coli bacteria are Gram-negative, non-spore-forming aerobes or facultative anaerobic rods. Some strains are pathogenic in men while others are commensals in the gut. The pathogenic strains cause a wide array of diseases by virtue of virulence factors. The commensal strains are generally categorized into phylogenetic groups A and B1. The aim of this study was to determine the association between phylogeny of E. coli isolates and virulence and sociodemographic characteristics of the study subjects. Method. This study was a cross-sectional study carried out from July 2018 to June 2019. E. coli isolates obtained from different clinical specimens were subjected to polymerase chain reaction to determine their phylogenetic groupings and virulence. Results. The majority of the isolates belonged to phylogroup A 101 (74.8%), and the predominant virulent gene was fimA (88.9%). There was no significant correlation between phylogenicity and virulence, except for chuA which was found in all isolates that belonged to phylogroups clade I and D. None of the 101 isolates that belonged to group A had the chuA virulence gene. There was a significant association between patient age category and phylogenetic groups B1 and D. Conclusions. This study assessed the relationship between the phylogenetic distribution and the virulence profile of clinical isolates of E. coli. The virulence of isolates belonging to phylogroup A, which are generally considered as commensals, is alarming. Measures must therefore be put in place to control the spread of these virulent E. coli.

Studies on Virulence and Extended-Spectrum β-Lactamase-Producing Uropathogenic Escherichia coli Isolates and Therapeutic Effect of Fosfomycin in Acute Pyelonephritis Mice

The understanding about virulence factors (VFs) and the drug resistance of uropathogenic Escherichia coli (UPEC) helps us understand the pathogenesis of urinary tract infections (UTIs) and make better decisions for clinical treatment. This study examined the correlation between the extended-spectrum β-lactamases (ESBLs) phenotype and VFs in UPEC strains. In addition, we validated the therapeutic potential of fosfomycin in acute pyelonephritis mice. From May 2017 to November 2018, 22 nonduplicate E coli. strains were isolated from UTI patients. PCR was utilized to detect the distribution of virulence genes. We also analyzed the ESBL phenotype in E coli. We further evaluated the therapeutic effect of intravenous fosfomycin treatment in the acute pyelonephritis (APN) model. All 22 UPEC strains expressed the type 1 fimbriae (FimH) gene and more than 50% (12/22) of strains produced ESBLs. The detection rates of the iron acquisition-associated genes ChuT and IutA were 77.3% (n = 17) and 50% (n = 11) and those of P fimbria papA and papC genes were 45% (n = 10) and 50% (n = 11), respectively. Though the VFs were closely related with pathologenicity, the relationship between VFs and ESBLs still needs further investigation. Furthermore, intravenous fosfomycin 800 mg/kg significantly reduced the bacterial load and the inflammatory infiltration in the bladder and kidney, maintaining the structural integrity of the kidney. Intravenous fosfomycin administration can be used for the treatment of acute pyelonephritis caused by highly pathogenic and drug-resistant UPEC strains.

Multiple bacterial virulence factors focused on adherence and biofilm formation associate with outcomes in cirrhosis

BACKGROUND & AIMS

Altered gut microbiota is associated with poor outcomes in cirrhosis, including infections and hepatic encephalopathy (HE). However, the role of bacterial virulence factors (VFs) is unclear. Aim: Define association of VFs with cirrhosis severity and infections, their linkage with outcomes, and impact of fecal microbiota transplant (FMT).

METHODS

VF abundances were determined using metagenomic analysis in stools from controls and cirrhosis patients (compensated, HE-only, ascites-only, both and infected). Patients were followed for 90-day hospitalizations and 1-year death. Stool samples collected before/after a placebo-controlled FMT trial were also analyzed. Bacterial species and VFs for all species and selected pathogens (Escherichia, Klebsiella, Pseudomonas, Staphylococcus, Streptococcus, and Enterococcus spp) were compared between groups. Multi-variable analyses were performed for clinical biomarkers and VFs for outcome prediction. Changes in VFs pre/post-FMT and post-FMT/placebo were analyzed. Results: We included 233 subjects (40 controls, 43 compensated, 30 HE-only, 20 ascites-only, 70 both, and 30 infected). Decompensated patients, especially those with infections, had higher VFs coding for siderophores, biofilms, and adhesion factors versus the rest. Biofilm and adhesion VFs from Enterobacteriaceae and Enterococcus spp associated with death and hospitalizations independent of clinical factors regardless of when all VFs or selected pathogens were analyzed. FMT was associated with reduced VF post-FMT versus pre-FMT and post-placebo groups.

CONCLUSIONS

Virulence factors from multiple species focused on adhesion and biofilms increased with decompensation and infections, associated with death and hospitalizations independent of clinical factors, and were attenuated with FMT. Strategies focused on targeting multiple virulence factors could potentially impact outcomes in cirrhosis.

PRESENTATIONS

Portions of this manuscript were an oral presentation in the virtual International Liver Congress 2021.

ABBREVIATIONS

VF: virulence factors, HE: hepatic encephalopathy, FMT: Fecal microbiota transplant, PPI: proton pump inhibitors, LPS: lipopolysaccharides, VFDB: Virulence factor database, OTU: operational taxonomic units, SBP: spontaneous bacterial peritonitis, UTI: urinary tract infections, MRSA: methicillin resistant Staphylococcus aureus, VRE: vancomycin-resistant Enterococcus, MAAsLin2: Microbiome Multivariable Associations with Linear Models, LPS: lipopolysaccharides, AKI: acute kidney injury.

A semi high-throughput method for real-time monitoring of curli producing Salmonella biofilms on air-solid interfaces

Biofilms enable bacteria to colonize numerous ecological niches. Bacteria within a biofilm are protected by the extracellular matrix (ECM), of which the fibril-forming amyloid protein curli and polysaccharide cellulose are major components in members of Salmonella, Eschericha and Mycobacterium genus. A shortage of real-time detection methods has limited our understanding of how ECM production contributes to biofilm formation and pathogenicity. Here we present optotracing as a new semi-high throughput method for dynamic monitoring of Salmonella biofilm growth on air-solid interfaces. We show how an optotracer with binding-induced fluorescence acts as a dynamic fluorescent reporter of curli expression during biofilm formation on agar. Using spectrophotometry and microscopic imaging of fluorescence, we analyse in real-time the development of the curli architecture in relation to bacterial cells. With exceptional spatial and temporal precision, this revealed a well-structured, non-uniform distribution of curli organised in distally projecting radial channel patterns. Dynamic monitoring of the biofilm also showed defined regions undergoing different growth phases. ECM structures were found to assemble in regions of late exponential growth phase, suggesting that ECM forms on site after bacteria colonize the surface. As the optotracer biofilm method expedites screening of curli production, providing exceptional spatial-temporal understanding of the surface-associated biofilm lifestyle, this method adds a new technique to further our understanding of bacterial biofilms.

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Design and evaluation of a method for real-time biofilm experimentation.

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Optotracing enables real-time monitoring of biofilm formation on solid supports.

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Definitive biofilm monitoring by selective tracking of ECM components.

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A method reducing the inherent biases of morphotyping.

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A semi-high throughput method increasing the ease and efficiency of biofilm detection.

UPEC kidney infection triggers neuro-immune communication leading to modulation of local renal inflammation by splenic IFNγ

Bacterial infection results in a veritable cascade of host responses, both local and systemic. To study the initial stages of host-pathogen interaction in living tissue we use spatially-temporally controlled in vivo models. Using this approach, we show here that within 4 h of a uropathogenic Escherichia coli (UPEC) infection in the kidney, an IFNγ response is triggered in the spleen. This rapid infection-mediated inter-organ communication was found to be transmitted via nerve signalling. Bacterial expression of the toxin α-hemolysin directly and indirectly activated sensory neurons, which were identified in the basement membrane of renal tubules. Nerve activation was transmitted via the splenic nerve, inducing upregulation of IFNγ in the marginal zones of the spleen that led to increasing concentrations of IFNγ in the circulation. We found that IFNγ modulated the inflammatory signalling generated by renal epithelia cells in response to UPEC infection. This demonstrates a new concept in the host response to kidney infection; the role of nerves in sensing infection and rapidly triggering a systemic response which can modulate inflammation at the site of infection. The interplay between the nervous and immune systems is an exciting, developing field with the appealing prospect of non-pharmaceutical interventions. Our study identifies an important role for systemic neuro-immune communication in modulating inflammation during the very first hours of a local bacterial infection in vivo.

Defining chaperone-usher fimbriae repertoire in Serratia marcescens

Chaperone-usher (CU) fimbriae are surface organelles particularly prevalent among the Enterobacteriaceae. Mainly associated to their adhesive properties, CU fimbriae play key roles in biofilm formation and host cell interactions. Little is known about the fimbriome composition of the opportunistic human pathogen Serratia marcescens. Here, by using a search based on consensus fimbrial usher protein (FUP) sequences, we identified 421 FUPs across 39 S. marcescens genomes. Further analysis of the FUP-containing loci allowed us to classify them into 20 conserved CU operons, 6 of which form the S. marcescens core CU fimbriome. A new systematic nomenclature is proposed according to FUP sequence phylogeny. We also established an in vivo transcriptional assay comparing CU promoter expression between an environmental and a clinical isolate of S. marcescens, which revealed that promoters from 3 core CU operons (referred as fgov, fpo, and fps) are predominantly expressed in the two strains and might represent key core adhesion appendages contributing to S. marcescens pathogenesis.

Kidney intercalated cells are phagocytic and acidify internalized uropathogenic Escherichia coli

Kidney intercalated cells are involved in acid-base homeostasis via vacuolar ATPase expression. Here we report six human intercalated cell subtypes, including hybrid principal-intercalated cells identified from single cell transcriptomics. Phagosome maturation is a biological process that increases in biological pathway analysis rank following exposure to uropathogenic Escherichia coli in two of the intercalated cell subtypes. Real time confocal microscopy visualization of murine renal tubules perfused with green fluorescent protein expressing Escherichia coli or pHrodo Green E. coli BioParticles demonstrates that intercalated cells actively phagocytose bacteria then acidify phagolysosomes. Additionally, intercalated cells have increased vacuolar ATPase expression following in vivo experimental UTI. Taken together, intercalated cells exhibit a transcriptional response conducive to the kidney's defense, engulf bacteria and acidify the internalized bacteria. Intercalated cells represent an epithelial cell with characteristics of professional phagocytes like macrophages.

The Role of Antibiotic Resistant A. baumannii in the Pathogenesis of Urinary Tract Infection and the Potential of Its Treatment with the Use of Bacteriophage Therapy

Acinetobacter baumannii are bacteria that belong to the critical priority group due to their carbapenems and third generation cephalosporins resistance, which are last-chance antibiotics. The growing multi-drug resistance and the ability of these bacteria to form biofilms makes it difficult to treat infections caused by this species, which often affects people with immunodeficiency or intensive care unit patients. In addition, most of the infections are associated with catheterization of patients. These bacteria are causative agents, inter alia, of urinary tract infections (UTI) which can cause serious medical and social problems, because of treatment difficulties as well as the possibility of recurrence and thus severely decrease patients' quality of life. Therefore, a promising alternative to standard antibiotic therapy can be bacteriophage therapy, which will generate lower costs and will be safer for the treated patients and has real potential to be much more effective. The aim of the review is to outline the important role of drug-resistant A. baumannii in the pathogenesis of UTI and highlight the potential for fighting these infections with bacteriophage therapy. Further studies on the use of bacteriophages in the treatment of UTIs in animal models may lead to the use of bacteriophage therapy in human urinary tract infections caused by A. baumannii in the future.

The Indiana O'Brien Center for Advanced Renal Microscopic Analysis

The Indiana O'Brien Center for Advanced Microscopic Analysis is a National Institutes of Health (NIH) P30-funded research center dedicated to the development and dissemination of advanced methods of optical microscopy to support renal researchers throughout the world. The Indiana O'Brien Center was founded in 2002 as an NIH P-50 project with the original goal of helping researchers realize the potential of intravital multiphoton microscopy as a tool for understanding renal physiology and pathophysiology. The center has since expanded into the development and implementation of large-scale, high-content tissue cytometry. The advanced imaging capabilities of the center are made available to renal researchers worldwide via collaborations and a unique fellowship program. Center outreach is accomplished through an enrichment core that oversees a seminar series, an informational website, and a biennial workshop featuring hands-on training from members of the Indiana O'Brien Center and imaging experts from around the world.

A host receptor enables type 1 pilus-mediated pathogenesis of Escherichia coli pyelonephritis

Type 1 pili have long been considered the major virulence factor enabling colonization of the urinary bladder by uropathogenic Escherichia coli (UPEC). The molecular pathogenesis of pyelonephritis is less well characterized, due to previous limitations in preclinical modeling of kidney infection. Here, we demonstrate in a recently developed mouse model that beyond bladder infection, type 1 pili also are critical for establishment of ascending pyelonephritis. Bacterial mutants lacking the type 1 pilus adhesin (FimH) were unable to establish kidney infection in male C3H/HeN mice. We developed an in vitro model of FimH-dependent UPEC binding to renal collecting duct cells, and performed a CRISPR screen in these cells, identifying desmoglein-2 as a primary renal epithelial receptor for FimH. The mannosylated extracellular domain of human DSG2 bound directly to the lectin domain of FimH in vitro, and introduction of a mutation in the FimH mannose-binding pocket abolished binding to DSG2. In infected C3H/HeN mice, type 1-piliated UPEC and Dsg2 were co-localized within collecting ducts, and administration of mannoside FIM1033, a potent small-molecule inhibitor of FimH, significantly attenuated bacterial loads in pyelonephritis. Our results broaden the biological importance of FimH, specify the first renal FimH receptor, and indicate that FimH-targeted therapeutics will also have application in pyelonephritis.

Urinary tract infections (UTIs) are among the most common bacterial infections in humans. While much has been discovered about how E. coli cause bladder infections, less is known about the host-pathogen interactions that underlie kidney infection (pyelonephritis). We employed recently developed mouse models to show that bacterial surface fibers called type 1 pili, which bear the adhesive protein FimH and are known to mediate E. coli binding to bladder epithelium, are also required for ascending kidney infection. We developed a cell-culture model of bacterial binding to renal collecting duct, then performed a screen using the gene-editing tool CRISPR to identify the first known FimH receptor in the kidney. This epithelial cell-surface protein, desmoglein-2, was shown to directly bind FimH, and we localized this binding to specific extracellular domains of DSG2. Further, we showed that mannosides, small-molecule FimH inhibitors currently in development to treat bladder infection, are also effective in experimental kidney infection. Our study reveals a novel host-pathogen interaction during pyelonephritis and demonstrates how this interaction may be therapeutically targeted.

Distribution of phylogenetic groups, adhesin genes, biofilm formation, and antimicrobial resistance of uropathogenic Escherichia coli isolated from hospitalized patients in Thailand

BACKGROUND

Urinary tract infections (UTIs) are the most common bacterial infections and are often caused by uropathogenic Escherichia coli (UPEC). We investigated the distribution of phylogenetic groups, adhesin genes, antimicrobial resistance, and biofilm formation in E. coli isolated from patients with UTIs.

METHODS

In the present study, 208 UPEC isolated from Thai patients were classified into phylogenetic groups and adhesin genes were detected using multiplex PCR. Antimicrobial susceptibility testing was performed using agar disk diffusion. The Congo red agar method was used to determine the ability of the UPEC to form biofilm.

RESULTS

The most prevalent UPEC strains in this study belonged to phylogenetic group B2 (58.7%), followed by group C (12.5%), group E (12.0%), and the other groups (16.8%). Among adhesin genes, the prevalence of fimH (91.8%) was highest, followed by pap (79.3%), sfa (12.0%), and afa (7.7%). The rates of resistance to fluoroquinolones, trimethoprim-sulfamethoxazole, and amoxicillin-clavulanate were  65%, 54.3%, and 36.5%, respectively. The presence of adhesin genes and antibiotic resistance were more frequent in groups B2 and C compared to the other groups. Of the 129 multidrug-resistant UPEC strains, 54% were biofilm producers. Our findings further indicated that biofilm production was significantly correlated with the pap adhesin gene (p ≤ 0.05).

CONCLUSION

These findings provide molecular epidemiologic data, antibiotic resistance profiles, and the potential for biofilm formation among UPEC strains that can inform further development of the appropriate prevention and control strategies for UTIs in this region.

Adhesion of Escherichia Coli to Nanostructured Surfaces and the Role of Type 1 Fimbriae

Bacterial fimbriae are an important virulence factor mediating adhesion to both biotic and abiotic surfaces and facilitating biofilm formation. The expression of type 1 fimbriae of Escherichia coli is a key virulence factor for urinary tract infections and catheter-associated urinary tract infections, which represent the most common nosocomial infections. New strategies to reduce adhesion of bacteria to surfaces is therefore warranted. The aim of the present study was to investigate how surfaces with different nanotopography-influenced fimbriae-mediated adhesion. Surfaces with three different nanopattern surface coverages made in polycarbonate were fabricated by injection molding from electron beam lithography nanopatterned templates. The surfaces were constructed with features of approximately 40 nm width and 25 nm height with 100 nm, 250 nm, and 500 nm interspace distance, respectively. The role of fimbriae type 1-mediated adhesion was investigated using the E. coli wild type BW25113 and ΔfimA (with a knockout of major pilus protein FimA) and ΔfimH (with a knockout of minor protein FimH) mutants. For the surfaces with nanotopography, all strains adhered least to areas with the largest interpillar distance (500 nm). For the E. coli wild type, no difference in adhesion between surfaces without pillars and the largest interpillar distance was observed. For the deletion mutants, increased adhesion was observed for surfaces without pillars compared to surfaces with the largest interpillar distance. The presence of a fully functional type 1 fimbria decreased the bacterial adhesion to the nanopatterned surfaces in comparison to the mutants.

Escherichia coli FimH adhesins act synergistically with PapGII adhesins for enhancing establishment and maintenance of kidney infection

BACKGROUND

FimH adhesin is proposed to enhance Escherichia coli kidney infection by acting with PapGII adhesin, but genetic epidemiology study and animal study have not been widely conducted to confirm this hypothesis.

METHODS

We compared the prevalence of adhesin gene and their coexistent pattern between upper and lower urinary tract infection (UTI) strains. fimH mutant (EC114FM), papGII mutant (EC114PM) and fimH/papGII double mutant (EC114DM) were constructed from a pylonephritogenic strain (EC114). We compared among these strains for the infection ability in bladders and kidneys of female BALB/c mice challenged transurethrally with these bacteria and assessed 1, 3, and 7 days after inoculation.

RESULTS

Strains carrying fimH-only genotype were significantly more prevalent in lower UTI (P < 0.001). Strains carrying the fimH/papGII, but not papGII-only, were significantly associated with upper UTI (P = 0.001). Incidence of kidney infection increased after inoculation with EC114 on days 1 and 3, at both low and high dose, as compared with EC114DM; and the effect was greater than the sum of individual effect of EC114PM and EC114FM. Geometric means of quantitative bacterial counts in the kidneys significantly decreased when challenged with EC114FM on days 3 and 7, EC114PM on day 3 and EC114DM on day 1 after inoculation at high dose, as compared with EC114 (all P < 0.05).

CONCLUSIONS

We confirmed the advantage and synergistic action of FimH and PapGII for E. coli kidney infection and concluded that antagonists against FimH and PapGII adhesin may prevent kidney infection and enable its management.

Bacterial profile, antibiotic susceptibility pattern and associated risk factors of urinary tract infection among clinically suspected children attending at Felege-Hiwot comprehensive and specialized hospital, Northwest Ethiopia. A prospective study

Background

Urinary tract infection is one of the most common bacterial infections in children. Understanding the characteristics of uropathogens and their antimicrobial susceptibility pattern in a particular setting can provide evidence for the appropriate management of cases. This study aimed to assess the bacterial profile of urinary tract infection, their antimicrobial susceptibility pattern and associated factors among clinically suspected children attending at Felege-Hiwot Comprehensive Specialized Hospital, Northwest Ethiopia.

Methods

A hospital-based cross-sectional study was conducted from February–April, 2019. A systematic sampling technique was employed. A mid-stream urine sample was inoculated on cystine lactose electrolyte deficient media and incubated for 24–48 h. Sub-culturing was done on Mac-Conkey and blood agar. Antimicrobial susceptibility test was done on Muller-Hinton agar. A binary logistic regression model was used to see the association between dependent and independent factors. A p-value< 0.05 at 95% CI was considered as statistically significant.

Results

The overall prevalence of urinary tract infection was 16.7% (95% CI 12.4–21.1). Both Gram-negative and Gram-positive bacterial isolates were recovered with a rate of 44/50 (88%) and 6/50 (12%) respectively. Among Gram-negative isolates, E. coli 28/44(63.6%) was predominant while S. saprophyticus 2/6(33.3%) was prevalent among Gram-positive bacterial isolates. Overall, a high level of resistance to ampicillin, augmentin, and tetracycline was shown by Gram-negative bacteria with a rate of 44/44(100%), 39/44(88.6%), and36/44 (81.8%) respectively. About 33/50(66%) of overall multidrug resistance was observed (95% CI 52–78). About six Gram-negative bacterial isolates were extended spectrum beta-lactamase (ESBL) producers. Having a history of urinary tract infection (P-0.003, AOR 1.86–22.15) and male uncircumcision (p-0.00, AOR 5.5–65.35) were the independent variables that associate for urinary tract infections.

Conclusion

In the present study, the prevalence of urinary tract infection among children was high and considerably a high proportion of multidrug resistance was observed. This result will have a significant impact on the selection of appropriate antimicrobial agents for the treatment of urinary tract infection.

[Bacterial urinary tract infection and subclinical bacteriuria in the dog: a current review]

Bacterial urinary tract infection (UTI) is a common clinical presentation in dogs and a frequent reason for the prescription of antimicrobial drugs. UTI refers to adherence, multiplication and persistence of an infectious agent within the urogenital system. This causes an associated inflammatory response as well as the pertaining clinical signs. Depending on the site of infection, UTI's may be classified as bacterial cystitis, prostatitis or pyelonephritis. In contrast, subclinical bacteriuria (SB) is defined as the presence of a significant number of bacteria in the urine of an individual not showing clinical signs referrable to UTI. UTI's typically occur as a consequence of ascending pathogen migration from the host's own fecal or distal urogenital microbial flora. The most commonly isolated pathogen in cases of UTI and SB is Escherichia coli. The diagnosis is based on clinical signs and the results of urine examination and culture. The recently revised guidelines of the International Society for Companion Animal Infectious Diseases provide detailed recommendations for diagnosis and management of different forms of bacterial UTI's in dogs. Adherence to treatment guidelines will improve treatment success and is imperative in avoiding further deterioration of the antimicrobial resistance situation.

Alternative Therapeutic Options to Antibiotics for the Treatment of Urinary Tract Infections

Urinary tract infections (UTIs) mainly caused by Uropathogenic Escherichia coli (UPEC), are common bacterial infections. Many individuals suffer from chronically recurring UTIs, sometimes requiring long-term prophylactic antibiotic regimens. The global emergence of multi-drug resistant uropathogens in the last decade underlines the need for alternative non-antibiotic therapeutic and preventative strategies against UTIs. The research on non-antibiotic therapeutic options in UTIs has focused on the following phases of the pathogenesis: colonization, adherence of pathogens to uroepithelial cell receptors and invasion. In this review, we discuss vaccines, small compounds, nutraceuticals, immunomodulating agents, probiotics and bacteriophages, highlighting the challenges each of these approaches face. Most of these treatments show interesting but only preliminary results. Lactobacillus-containing products and cranberry products in conjunction with propolis have shown the most robust results to date and appear to be the most promising new alternative to currently used antibiotics. Larger efficacy clinical trials as well as studies on the interplay between non-antibiotic therapies, uropathogens and the host immune system are warranted.

Overcoming the challenge of establishing biofilms in vivo: a roadmap for Enterococci

Enterococcus faecalis forms single and mixed-species biofilms on both tissue and medical devices in the host, often under exposure to fluid flow, giving rise to infections that are recalcitrant to treatment. The factors that drive enterococcal biofilm formation in the host, however, remain unclear. Recent reports in other pathogens show how surface sensing by bacteria can trigger the transition from planktonic to sessile lifestyle. Fluid flow can enhance initial adhesion, but also influence quorum sensing. Biofilm-specific factors, as well as biofilm size and extracellular polymeric substances, can compromise opsonization and phagocytosis. Bacterial interspecies synergy can create favorable conditions in the host for biofilm formation. Through these concepts, we define the knowledge gaps in understanding host-associated E. faecalis biofilm formation and propose a roadmap for future investigations.

Nitrate Metabolism Modulates Biosynthesis of Biofilm Components in Uropathogenic Escherichia coli and Acts as a Fitness Factor During Experimental Urinary Tract Infection

To successfully colonize a variety of environments, bacteria can coordinate complex collective behaviors such as biofilm formation. To thrive in oxygen limited niches, bacteria’s versatile physiology enables the utilization of alternative electron acceptors. Nitrate, the second most favorable electron acceptor after oxygen, plays a prominent role in the physiology of uropathogenic Escherichia coli (UPEC) and is abundantly found in urine. Here we analyzed the role of extracellular nitrate in the pathogenesis of the UPEC strain CFT073 with an initial focus on biofilm formation. Colony morphotyping in combination with extensive mutational, transcriptional, and protein expression analyses of CFT073 wild-type and mutants deficient in one or several nitrate reductases revealed an association between nitrate reduction and the biosynthesis of biofilm extracellular matrix components. We identified a role for the nitrate response regulator NarL in modulating expression of the biofilm master regulator CsgD. To analyze the role of nitrate reduction during infection in vivo, we tested wild-type CFT073 and a nitrate reductase null mutant in an ascending urinary tract infection (UTI) model. Individually, each strain colonized extensively, suggesting that nitrate reduction is expendable during UTI. However, during competitive co-infection, the strain incapable of nitrate reduction was strongly outcompeted. This suggests that nitrate reduction can be considered a non-essential but advantageous fitness factor for UPEC pathogenesis. This implies that UPEC rapidly adapts their metabolic needs to the microenvironment of infected tissue. Collectively, this work demonstrates a unique association between nitrate respiration, biofilm formation, and UPEC pathogenicity, highlighting how the use of alternative electron acceptors enables bacterial pathogens to adapt to challenging infectious microenvironments.

In vitro assessment of pathogenicity and virulence encoding gene profiles of avian pathogenic Escherichia coli strains associated with colibacillosis in chickens

BACKGROUND

Avian pathogenic Escherichia coli (APEC) strains have been associated with various disease conditions in avian species due to virulence attributes associated with the organism.

AIMS

This study was carried out to determine the in vitro pathogenic characteristics and virulence encoding genes found in E. coli strains associated with colibacillosis in chickens.

METHODS

Fifty-two stock cultures of E. coli strains isolated from chickens diagnosed of colibacillosis were tested for their ability to produce haemolysis on blood agar and take up Congo red dye. Molecular characterization was carried out by polymerase chain reaction (PCR) amplification of virulence encoding genes associated with APEC.

RESULTS

Eleven (22%) and 41 (71%) were positive for haemolysis on 5% sheep red blood agar and Congo red agar, respectively. Nine virulence-associated genes were detected as follows: FimH (96%), csgA (52%), iss (48%), iut (33%), tsh (21%), cva (15%), kpsII (10%), pap (2%), and felA (2%).

CONCLUSION

The APEC strains exhibited virulence properties and harbored virulence encoding genes which could be a threat to the poultry population and public health. The putative virulence genes were diverse and different in almost all isolate implying that pathogenesis was multi-factorial and the infection was multi-faceted which could be a source of concern in the detection and control of APEC infections.

Time-resolved dual RNA-seq of tissue uncovers Pseudomonas plecoglossicida key virulence genes in host-pathogen interaction with Epinephelus coioides

Bacterial pathogen-host interactions are highly dynamic, regulated processes that have been primarily investigated using in vitro assays. The dynamics of bacterial pathogen-host interplay in vivo are poorly understood. Using time-resolved dual RNA-seq in a Pseudomonas plecoglossicida-Epinephelus coioides infection model, we observed that bacterial genes encoding classical virulence factors and host genes involved in immune regulation were dynamically expressed during infection. Using network inferencing, we were able to predict interspecies regulatory networks linking bacterial virulence genes to host immune genes. Together with gene co-expression network analysis of the pathogen, secY was predicted to be a key virulence gene for P. plecoglossicida pathogenicity in the host, fliN was predicted to be a less important virulence gene. The results of bioinformatics prediction were confirmed by animal infection experiments. Our work provides the first paradigm to study dynamic alterations of bacterial pathogen and host interactions based on the elucidation of time-resolved interactive transcriptomes in vivo, and may be developed into a novel and universal method for revealing the true complexity of the bacterial infection process.

High Resolution Intravital Imaging of the Renal Immune Response to Injury and Infection in Mice

We developed an experimental set up that enables longitudinal studies of immune cell behavior in situ in the challenged as well as unchallenged kidney of anesthetized mice over several hours. Using highly controlled vacuum to stabilize the kidney, the superficial renal cortex could continuously be visualized with minimal disruption of the local microenvironment. No visible changes in blood flow or neutrophils and macrophages numbers were observed after several hours of visualizing the unchallenged kidney, indicating a stable tissue preparation without apparent tissue damage. Applying this set up to monocyte/macrophage (CX3CR1GFP/+) reporter mice, we observed the extensive network of stellate-shaped CX3CR1 positive cells (previously identified as renal mononuclear phagocytes). The extended dendrites of the CX3CR1 positive cells were found to bridge multiple capillaries and tubules and were constantly moving. Light induced sterile tissue injury resulted in rapid neutrophil accumulation to the site of injury. Similarly, microinfusion of uropathogenic Escherichia coli into a single nephron induced a rapid and massive recruitment of neutrophils to the site of infection, in addition to active bacterial clearance by neutrophils. In contrast, the kidney resident mononuclear phagocytes were observed to not increase in numbers or migrate toward the site of injury or infection. In conclusion, this model allows for longitudinal imaging of responses to localized kidney challenges in the mouse.

clpV is a key virulence gene during in vivo Pseudomonas plecoglossicida infection

Interaction between bacterial pathogen and aquatic animal host is exceedingly complex, which involves large dynamic changes in gene expression during different stages of the disease. However, research on identifying key virulence genes based on the dynamics of gene expression changes of a one-sided bacterial pathogen in tissue has not been reported so far across different stages of infectious disease. The clpV for the T6SS of Pseudomonas plecoglossicida was identified for a candidate for key virulence gene based on dynamic changes of gene expression. For the Epinephelus coioides infected using clpV-RNAi strain, no deaths were observed up to 20 dpi. The spleens, kidneys and livers of all the E. coioides that received clpV-RNAi strain failed to develop visible nodules at 5-8 dpi, with the swelling gradually disappearing. The burdens of clpV-RNAi strain in the spleen and blood were greatly reduced at most of the time points after injection, and the burdens of clpV-RNAi strain in the head kidneys and trunk kidneys also had a sharp reduction from 72 to 120 hpi. This paper provides a new insight into the discovery of key virulence genes of pathogens in infected tissue systems.

A Cinematic View of Tissue Microbiology in the Live Infected Host

Tissue microbiology allows for the study of bacterial infection in the most clinically relevant microenvironment, the living host. Advancements in techniques and technology have facilitated the development of novel ways of studying infection. Many of these advancements have come from outside the field of microbiology. In this article, we outline the progression from bacteriology through cellular microbiology to tissue microbiology, highlighting seminal studies along the way. We outline the enormous potential but also some of the challenges of the tissue microbiology approach. We focus on the role of emerging technologies in the continual development of infectious disease research and highlight future possibilities in our ongoing quest to understand host-pathogen interaction.

Reaching the End of the Line: Urinary Tract Infections

Urinary tract infections (UTIs) cause a substantial health care burden. UTIs (i) are most often caused by uropathogenic Escherichia coli (UPEC), (ii) primarily affect otherwise healthy females (50% of women will have a UTI), (iii) are associated with significant morbidity and economic impact, (iv) can become chronic, and (v) are highly recurrent. A history of UTI is a significant risk factor for a recurrent UTI (rUTI). In otherwise healthy women, an acute UTI leads to a 25 to 50% chance of rUTI within months of the initial infection. Interestingly, rUTIs are commonly caused by the same strain of E. coli that led to the initial infection, arguing that there exist host-associated reservoirs, like the gastrointestinal tract and underlying bladder tissue, that can seed rUTIs. Additionally, catheter-associated UTIs (CAUTI), caused by Enterococcus and Staphylococcus as well as UPEC, represent a major health care concern. The host's response of depositing fibrinogen at the site of infection has been found to be critical to establishing CAUTI. The Drug Resistance Index, an evaluation of antibiotic resistance, indicates that UTIs have become increasingly difficult to treat since the mid-2000s. Thus, UTIs are a "canary in the coal mine," warning of the possibility of a return to the preantibiotic era, where some common infections are untreatable with available antibiotics. Numerous alternative strategies for both the prevention and treatment of UTIs are being pursued, with a focus on the development of vaccines and small-molecule inhibitors targeting virulence factors, in the hopes of reducing the burden of urogenital tract infections in an antibiotic-sparing manner.

Efficiency of the flagellar propulsion of Escherichia coli in confined microfluidic geometries

Bacterial movement in confined spaces is routinely encountered either in a natural environment or in artificial structures. Consequently, the ability to understand and predict the behavior of motile bacterial cells in confined geometries is essential to many applications, spanning from the more classical, such as the management complex microbial networks involved in diseases, biomanufacturing, mining, and environment, to the more recent, such as single cell DNA sequencing and computation with biological agents. Fortunately, the development of this understanding can be helped by the decades-long advances in semiconductor microfabrication, which allow the design and the construction of complex confining structures used as test beds for the study of bacterial motility. To this end, here we use microfabricated channels with varying sizes to study the interaction of Escherichia coli with solid confining spaces. It is shown that an optimal channel size exists for which the hydrostatic potential allows the most efficient movement of the cells. The improved understanding of how bacteria move will result in the ability to design better microfluidic structures based on their interaction with bacterial movement.

Biocide Exposure Induces Changes in Susceptibility, Pathogenicity, and Biofilm Formation in Uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) is a frequent cause of catheter-associated urinary tract infection (CAUTI). Biocides have been incorporated into catheter coatings to inhibit bacterial colonization while, ideally, exhibiting low cytotoxicity and mitigating the selection of resistant bacterial populations. We compared the effects of long-term biocide exposure on susceptibility, biofilm formation, and relative pathogenicity in eight UPEC isolates. MICs, minimum bactericidal concentrations (MBCs), minimum biofilm eradication concentrations (MBECs), and antibiotic susceptibilities were determined before and after long-term exposure to triclosan, polyhexamethylene biguanide (PHMB), benzalkonium chloride (BAC), and silver nitrate. Biofilm formation was quantified using a crystal violet assay, and relative pathogenicity was assessed via a Galleria mellonella waxworm model. Cytotoxicity and the resulting biocompatibility index values were determined by use of an L929 murine fibroblast cell line. Biocide exposure resulted in multiple decreases in biocide susceptibility in planktonic and biofilm-associated UPEC. Triclosan exposure induced the largest frequency and magnitude of susceptibility decreases at the MIC, MBC, and MBEC, which correlated with an increase in biofilm biomass in all isolates. Induction of antibiotic cross-resistance occurred in 6/84 possible combinations of bacteria, biocide, and antibiotic. Relative pathogenicity significantly decreased after triclosan exposure (5/8 isolates), increased after silver nitrate exposure (2/8 isolates), and varied between isolates for PHMB and BAC. The biocompatibility index ranked the antiseptic potential as PHMB > triclosan > BAC > silver nitrate. Biocide exposure in UPEC may lead to reductions in biocide and antibiotic susceptibility, changes in biofilm formation, and alterations in relative pathogenicity. These data indicate the multiple consequences of biocide adaptation that should be considered when selecting an anti-infective catheter-coating agent.

Structural basis for usher activation and intramolecular subunit transfer in P pilus biogenesis in Escherichia coli

Chaperone-usher pathway pili are extracellular proteinaceous fibres ubiquitously found on Gram-negative bacteria, and mediate host-pathogen interactions and biofilm formation critical in pathogenesis in numerous human diseases1. During pilus assembly, an outer membrane macromolecular machine called the usher catalyses pilus biogenesis from the individual subunits that are delivered as chaperone-subunit complexes in the periplasm. The usher orchestrates pilus assembly using all five functional domains: a 24-stranded transmembrane β-barrel translocation domain, a β-sandwich plug domain, an amino-terminal periplasmic domain and two carboxy-terminal periplasmic domains (CTD1 and CTD2)2-6. Despite extensive structural and functional characterization, the mechanism by which the usher is activated to initiate pilus biogenesis is unknown. Here, we present the crystal structure of the full-length PapC usher from Escherichia coli in complex with its cognate PapDG chaperone-subunit complex in a pre-activation state, elucidating molecular details of how the usher is specifically engaged by allosteric interactions with its substrate preceding activation and how the usher facilitates the transfer of subunits from the amino-terminal periplasmic domain to the CTDs during pilus assembly. This work elucidates the intricate workings of a molecular machine that catalyses chaperone-usher pathway pilus assembly and opens the door for the development of potent inhibitors to block pilus biogenesis.

Protective vascular coagulation in response to bacterial infection of the kidney is regulated by bacterial lipid A and host CD147

Bacterial infection of the kidney leads to a rapid cascade of host protective responses, many of which are still poorly understood. We have previously shown that following kidney infection with uropathogenic Escherichia coli (UPEC), vascular coagulation is quickly initiated in local perivascular capillaries that protects the host from progressing from a local infection to systemic sepsis. The signaling mechanisms behind this response have not however been described. In this study, we use a number of in vitro and in vivo techniques, including intravital microscopy, to identify two previously unrecognized components influencing this protective coagulation response. The acylation state of the Lipid A of UPEC lipopolysaccharide (LPS) is shown to alter the kinetics of local coagulation onset in vivo. We also identify epithelial CD147 as a potential host factor influencing infection-mediated coagulation. CD147 is expressed by renal proximal epithelial cells infected with UPEC, contingent to bacterial expression of the α-hemolysin toxin. The epithelial CD147 subsequently can activate tissue factor on endothelial cells, a primary step in the coagulation cascade. This study emphasizes the rapid, multifaceted response of the kidney tissue to bacterial infection and the interplay between host and pathogen during the early hours of renal infection.