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

T3SS protein EsrC binds to the lacI-like operator of type 1 fimbrial operon to suppress adhesion of Edwardsiella piscicida

Type 1 fimbria, the short hair-like appendage assembled on the bacterial surface, plays a pivotal role in adhesion and invasion in Edwardsiella piscicida. The type III secretion system (T3SS), another bacterial surface appendage, facilitates E. piscicida's replication in vivo by delivering effectors into host cells. Our previous research demonstrated that E. piscicida T3SS protein EseJ inhibits adhesion and invasion of E. piscicida by suppressing type 1 fimbria. However, how EseJ suppresses type 1 fimbria remains elusive. In this study, a lacI-like operator (nt -245 to -1 of fimA) upstream of type 1 fimbrial operon in E. piscicida was identified, and EseJ inhibits type 1 fimbria through the lacI-like operator. Moreover, through DNA pull-down and electrophoretic mobility shift assay, an AraC-type T3SS regulator, EsrC, was screened and verified to bind to nt -145 to -126 and nt -50 to -1 of fimA, suppressing type 1 fimbria. EseJ is almost abolished upon the depletion of EsrC. EsrC and EseJ impede type 1 fimbria expression. Intriguingly, nutrition and microbiota-derived indole activate type 1 fimbria through downregulating T3SS, alleviating EsrC or EseJ's inhibitory effect on lacI-like operator of type 1 fimbrial operon. By this study, it is revealed that upon entering the gastrointestinal tract, rich nutrients and indole downregulate T3SS and thereof upregulate type 1 fimbria, stimulating efficient adhesion and invasion; upon being internalized into epithelium, the limit in indole and nutrition switches on T3SS and thereof switches off type 1 fimbria, facilitating effector delivery to guarantee E. piscicida's survival/replication in vivo.IMPORTANCEIn this work, we identified the lacI-like operator of type 1 fimbrial operon in E. piscicida, which was suppressed by the repressors-T3SS protein EseJ and EsrC. We unveiled that E. piscicida upregulates type 1 fimbria upon sensing rich nutrition and the microbiota-derived indole, thereof promoting the adhesion of E. piscicida. The increase of indole and nutrition promotes type 1 fimbria by downregulating T3SS. The decrease in EseJ and EsrC alleviates their suppression on type 1 fimbria, and vice versa.

Medical Device-Associated Biofilm Infections and Multidrug-Resistant Pathogens

Medical devices such as venous catheters (VCs) and urinary catheters (UCs) are widely used in the hospital setting. However, the implantation of these devices is often accompanied by complications. About 60 to 70% of nosocomial infections (NIs) are linked to biofilms. The main complication is the ability of microorganisms to adhere to surfaces and form biofilms which protect them and help them to persist in the host. Indeed, by crossing the skin barrier, the insertion of VC inevitably allows skin flora or accidental environmental contaminants to access the underlying tissues and cause fatal complications like bloodstream infections (BSIs). In fact, 80,000 central venous catheters-BSIs (CVC-BSIs)-mainly occur in intensive care units (ICUs) with a death rate of 12 to 25%. Similarly, catheter-associated urinary tract infections (CA-UTIs) are the most commonlyhospital-acquired infections (HAIs) worldwide.These infections represent up to 40% of NIs.In this review, we present a summary of biofilm formation steps. We provide an overview of two main and important infections in clinical settings linked to medical devices, namely the catheter-asociated bloodstream infections (CA-BSIs) and catheter-associated urinary tract infections (CA-UTIs), and highlight also the most multidrug resistant bacteria implicated in these infections. Furthermore, we draw attention toseveral useful prevention strategies, and advanced antimicrobial and antifouling approaches developed to reduce bacterial colonization on catheter surfaces and the incidence of the catheter-related infections.

Current and emerging strategies to curb antibiotic-resistant urinary tract infections

Rising rates of antibiotic resistance in uropathogenic bacteria compromise patient outcomes and prolong hospital stays. Consequently, new strategies are needed to prevent and control the spread of antibiotic resistance in uropathogenic bacteria. Over the past two decades, sizeable clinical efforts and research advances have changed urinary tract infection (UTI) treatment and prevention strategies to conserve antibiotic use. The emergence of antimicrobial stewardship, policies from national societies, and the development of new antimicrobials have shaped modern UTI practices. Future UTI management practices could be driven by the evolution of antimicrobial stewardship, improved and readily available diagnostics, and an improved understanding of how the microbiome affects UTI. Forthcoming UTI treatment and prevention strategies could employ novel bactericidal compounds, combinations of new and classic antimicrobials that enhance bacterial killing, medications that prevent bacterial attachment to uroepithelial cells, repurposing drugs, and vaccines to curtail the rising rates of antibiotic resistance in uropathogenic bacteria and improve outcomes in people with UTI.

Urinary Tract Infections in Children

Despite the American Academy of Pediatrics guidelines for the evaluation, treatment, and management of urinary tract infections (UTIs), UTI diagnosis and management remains challenging for clinicians. Challenges with acute UTI management stem from vague presenting signs and symptoms, diagnostic uncertainty, limitations in laboratory testing, and selecting appropriate antibiotic therapy in an era with increasing rates of antibiotic-resistant uropathogens. Recurrent UTI management remains difficult due to an incomplete understanding of the factors contributing to UTI, when to assess a child with repeated infections for kidney and urinary tract anomalies, and limited prevention strategies. To help reduce these uncertainties, this review provides a comprehensive overview of UTI epidemiology, risk factors, diagnosis, treatment, and prevention strategies that may help pediatricians overcome the challenges associated with acute and recurrent UTI management.

Intercalated cell function, kidney innate immunity, and urinary tract infections

Intercalated cells (ICs) in the kidney collecting duct have a versatile role in acid-base and electrolyte regulation along with the host immune defense. Located in the terminal kidney tubule segment, ICs are among the first kidney cells to encounter bacteria when bacteria ascend from the bladder into the kidney. ICs have developed several mechanisms to combat bacterial infections of the kidneys. For example, ICs produce antimicrobial peptides (AMPs), which have direct bactericidal activity, and in many cases are upregulated in response to infections. Some AMP genes with IC-specific kidney expression are multiallelic, and having more copies of the gene confers increased resistance to bacterial infections of the kidney and urinary tract. Similarly, studies in human children demonstrate that those with history of UTIs are more likely to have single-nucleotide polymorphisms in IC-expressed AMP genes that impair the AMP's bactericidal activity. In murine models, depleted or impaired ICs result in decreased clearance of bacterial load following transurethral challenge with uropathogenic E. coli. A 2021 study demonstrated that ICs even act as phagocytes and acidify bacteria within phagolysosomes. Several immune signaling pathways have been identified in ICs which may represent future therapeutic targets in managing kidney infections or inflammation. This review's objective is to highlight IC structure and function with an emphasis on current knowledge of IC's diverse innate immune capabilities.

Discovery of Orally Bioavailable FmlH Lectin Antagonists as Treatment for Urinary Tract Infections

FmlH, a bacterial adhesin of uropathogenic Escherichia coli (UPEC), has been shown to provide a fitness advantage in colonizing the bladder during chronic urinary tract infections (UTIs). Previously reported ortho-biphenyl glycosides based on βGal and βGalNAc have excellent binding affinity to FmlH and potently block binding to its natural carbohydrate receptor, but they lack oral bioavailability. In this paper, we outline studies where we have optimized compounds for improved pharmacokinetics, leading to the discovery of novel analogues with good oral bioavailability. We synthesized galactosides with the anomeric O-linker replaced with more stable S- and C-linked linkers. We also investigated modifications to the GalNAc sugar and modifications to the biphenyl aglycone. We identified GalNAc 69 with an IC50 of 0.19 μM against FmlH and 53% oral bioavailability in mice. We also obtained a FimlH-bound X-ray structure of lead compound 69 (AM4085) which has potential as a new antivirulence therapeutic for UTIs.

Uropathogen and host responses in pyelonephritis

Urinary tract infections (UTIs) are among the most common bacterial infections seen in clinical practice. The ascent of UTI-causing pathogens to the kidneys results in pyelonephritis, which can trigger kidney injury, scarring and ultimately impair kidney function. Despite sizable efforts to understand how infections develop or are cleared in the bladder, our appreciation of the mechanisms by which infections develop, progress or are eradicated in the kidney is limited. The identification of virulence factors that are produced by uropathogenic Escherichia coli to promote pyelonephritis have begun to fill this knowledge gap, as have insights into the mechanisms by which kidney tubular epithelial cells oppose uropathogenic E. coli infection to prevent or eradicate UTIs. Emerging data also illustrate how specific cellular immune responses eradicate infection whereas other immune cell populations promote kidney injury. Insights into the mechanisms by which uropathogenic E. coli circumvent host immune defences or antibiotic therapy to cause pyelonephritis is paramount to the development of new prevention and treatment strategies to mitigate pyelonephritis and its associated complications.

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.

Immune defenses in the urinary tract

Recent advances in preclinical modeling of urinary tract infections (UTIs) have enabled the identification of key facets of the host response that influence pathogen clearance and tissue damage. Here, we review new insights into the functions of neutrophils, macrophages, and antimicrobial peptides in innate control of uropathogens and in mammalian infection-related tissue injury and repair. We also discuss novel functions for renal epithelial cells in innate antimicrobial defense. In addition, epigenetic modifications during bacterial cystitis have been implicated in bladder remodeling, conveying susceptibility to recurrent UTI. In total, contemporary work in this arena has better defined host processes that shape UTI susceptibility and severity and might inform the development of novel preventive and therapeutic approaches for acute and recurrent UTI.

Uncharacterized and lineage-specific accessory genes within the Proteus mirabilis pan-genome landscape

Proteus mirabilis is a Gram-negative bacterium recognized for its unique swarming motility and urease activity. A previous proteomic report on four strains hypothesized that, unlike other Gram-negative bacteria, P. mirabilis may not exhibit significant intraspecies variation in gene content. However, there has not been a comprehensive analysis of large numbers of P. mirabilis genomes from various sources to support or refute this hypothesis. We performed comparative genomic analysis on 2,060 Proteus genomes. We sequenced the genomes of 893 isolates recovered from clinical specimens from three large US academic medical centers, combined with 1,006 genomes from NCBI Assembly and 161 genomes assembled from Illumina reads in the public domain. We used average nucleotide identity (ANI) to delineate species and subspecies, core genome phylogenetic analysis to identify clusters of highly related P. mirabilis genomes, and pan-genome annotation to identify genes of interest not present in the model P. mirabilis strain HI4320. Within our cohort, Proteus is composed of 10 named species and 5 uncharacterized genomospecies. P. mirabilis can be subdivided into three subspecies; subspecies 1 represented 96.7% (1,822/1,883) of all genomes. The P. mirabilis pan-genome includes 15,399 genes outside of HI4320, and 34.3% (5,282/15,399) of these genes have no putative assigned function. Subspecies 1 is composed of several highly related clonal groups. Prophages and gene clusters encoding putatively extracellular-facing proteins are associated with clonal groups. Uncharacterized genes not present in the model strain P. mirabilis HI4320 but with homology to known virulence-associated operons can be identified within the pan-genome. IMPORTANCE Gram-negative bacteria use a variety of extracellular facing factors to interact with eukaryotic hosts. Due to intraspecies genetic variability, these factors may not be present in the model strain for a given organism, potentially providing incomplete understanding of host-microbial interactions. In contrast to previous reports on P. mirabilis, but similar to other Gram-negative bacteria, P. mirabilis has a mosaic genome with a linkage between phylogenetic position and accessory genome content. P. mirabilis encodes a variety of genes that may impact host-microbe dynamics beyond what is represented in the model strain HI4320. The diverse, whole-genome characterized strain bank from this work can be used in conjunction with reverse genetic and infection models to better understand the impact of accessory genome content on bacterial physiology and pathogenesis of infection.

Dynamics of Urinary Extracellular DNA in Urosepsis

Extracellular DNA (ecDNA) is a promising candidate marker for the early diagnosis and monitoring of urinary tract infections (UTIs). The aim of our study is to describe the dynamics of ecDNA in the plasma and urine of patients with urosepsis as well as in a mouse model of UTI. Samples of blood and urine were collected from adult patients with UTIs and obstructive uropathy (n = 36) during the first 3 days at the hospital and during a follow-up. Bacterial burden and urinary ecDNA were evaluated in a mouse UTI model (n = 26) at baseline; 24, 48, and 72 h after UTI induction; and 7 days after UTI induction. The plasma ecDNA did not change during urosepsis, but the plasma DNase activity increased significantly at the follow-up. The urinary ecDNA decreased significantly during hospitalization and remained low until the follow-up (90% lower vs. admission). No change was seen in the urinary DNase activity. C-reactive protein (CRP) and procalcitonin are positively correlated with plasma and urinary ecDNA. A UTI caused sepsis in 23% of mice. The urinary ecDNA decreased by three-fold and remained low until day 7 post-infection. Urinary bacterial burden is correlated with urinary ecDNA. Urinary ecDNA is a potential non-invasive marker for monitoring the effects of treatment during urosepsis and is related to UTI progression in the experimental animal model.

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.

Distinct ecological fitness factors coordinated by a conserved Escherichia coli regulator during systemic bloodstream infection

The ability of bacterial pathogens to adapt to host niches is driven by the carriage and regulation of genes that benefit pathogenic lifestyles. Genes that encode virulence or fitness-enhancing factors must be regulated in response to changing host environments to allow rapid response to challenges presented by the host. Furthermore, this process can be controlled by preexisting transcription factors (TFs) that acquire new roles in tailoring regulatory networks, specifically in pathogens. However, the mechanisms underlying this process are poorly understood. The highly conserved Escherichia coli TF YhaJ exhibits distinct genome-binding dynamics and transcriptome control in pathotypes that occupy different host niches, such as uropathogenic E. coli (UPEC). Here, we report that this important regulator is required for UPEC systemic survival during murine bloodstream infection (BSI). This advantage is gained through the coordinated regulation of a small regulon comprised of both virulence and metabolic genes. YhaJ coordinates activation of both Type 1 and F1C fimbriae, as well as biosynthesis of the amino acid tryptophan, by both direct and indirect mechanisms. Deletion of yhaJ or the individual genes under its control leads to attenuated survival during BSI. Furthermore, all three systems are up-regulated in response to signals derived from serum or systemic host tissue, but not urine, suggesting a niche-specific regulatory trigger that enhances UPEC fitness via pleiotropic mechanisms. Collectively, our results identify YhaJ as a pathotype-specific regulatory aide, enhancing the expression of key genes that are collectively required for UPEC bloodstream pathogenesis.

Neutrophil extracellular traps in urinary tract infection

Background

Urinary tract infections (UTI) are common types of bacterial infection in children. UTI treatment is aimed to prevent complications including hypertension, proteinuria, and progression to chronic kidney disease. Activated neutrophils release chromatin-based structures associated with antimicrobial proteins called neutrophil extracellular traps (NETs). We aimed to describe the role of NET-associated markers in children with UTI as well as the role of NETs formation in a mouse model of UTI.

Materials and methods

Markers of NETs including extracellular DNA (ecDNA), myeloperoxidase (MPO) and cathelicidin were analyzed in children with febrile UTI caused by E. coli (n = 98, aged 0.3-1.3 years) and in healthy controls (n = 50, 0.5-5.2 years). Moreover, an acute experimental model of UTI was performed on PAD4 knock-out mice with diminished NETs formation (n = 18), and on wild-type mice (n = 15).

Results

Children with UTI had significantly higher urinary NETs markers including total ecDNA, nuclear DNA and mitochondrial DNA, altogether with MPO and cathelicidin. The concentrations of MPO and cathelicidin positively correlated with ecDNA (r = 0.53, p ≤ 0.001; r = 0.56, p ≤ 0.001, respectively) and the number of leukocytes in the urine (r = 0.29, p ≤ 0.05; r = 0.27, p ≤ 0.05, respectively). Moreover, urinary MPO was positively associated with cathelicidin (r = 0.61, p ≤ 0.001). In the experimental model, bacterial load in the bladder (20-fold) and kidneys (300-fold) was significantly higher in PAD4 knock-out mice than in wild-type mice.

Conclusion

Higher urinary NETs makers-ecDNA, MPO and cathelicidin and their correlation with leukocyturia in children with UTI confirmed our hypothesis about the association between NETs and UTI in children. Higher bacterial load in mice with diminished NETs formation suggests that NETs are not only a simple consequence of UTI, but might play a direct role in the prevention of pyelonephritis and other UTI complications.

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

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

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.

High mannose level in bladder cancer enhances type 1 fimbria–mediated attachment of uropathogenic E. coli

Bladder cancer is the 4^th leading cancer in men. Tumor resection followed by bladder instillation of Bacillus Calmette-Guérin (BCG) is the primary treatment for high-risk patients with Non-Muscle Invasive Bladder Cancer (NMIBC) to prevent recurrence and progression to muscle-invasive disease. This treatment, however, lacks efficiency and causes severe adverse effects. Mannose residues are expressed on bladder surfaces and their levels were indicated to be higher in bladder cancer. Intravesical instillations of a recombinant Pseudomonas aeruginosa (PA) overexpressing the mannose-sensitive hemagglutination fimbriae (PA-MSHA), and of a mannose-specific lectin-drug conjugate showed efficiency against NMIBC in murine models of bladder cancer. Urothelial mannosylation facilitates bladder colonization by Uropathogenic E. coli (UPEC) via the interaction with the FimH mannose lectin, positioned at the tip of type 1 fimbria. A recombinant BCG strain overexpressing FimH on its outer surface, exhibited higher attachment and internalization to bladder cancer cells and increased effectivity in treating bladder cancer in mice. Investigating the pattern of mannose expression in NMIBC is important for improving treatment. Here, using tissue microarrays containing multiple normal and cancerous bladder samples, and lectins, we confirm that human bladder cancer cells express high mannose levels. Using UPEC mutants lacking or overexpressing type 1 fimbria, we also demonstrate that tumor-induced hypermannosylation increases type 1 fimbria mediated UPEC attachment to human and mouse bladder cancer. Our results provide an explanation for the effectiveness of PA-MSHA and the FimH-overexpressing BCG and support the hypothesis that mannose-targeted therapy holds potential for improving bladder cancer treatment.

Development of a hyper-adhesive and attenuated Edwardsiella ictaluri strain as a novel immersion vaccine candidate in yellow catfish (Pelteobagrus fulvidraco)

Edwardsiella ictaluri, a Gram-negative intracellular pathogen, is the causative agent of enteric septicemia in channel catfish, and catfish aquaculture in China suffers heavy economic losses due to E. ictaluri infection. Vaccination is an effective control measure for this disease. In this study, an attenuated E. ictaluri strain was acquired through deletion mutation of the T3SS protein eseJ_ei, and the ΔeseJ_ei strain fails to replicate in the epithelioma papillosum of carp cells. The type 1 fimbria plays a pivotal role in the adhesion of E. ictaluri, and it was found in this study that deletion of -245 to -50 nt upstream of fimA increases its adhesion to around five times that of the WT strain. A hyper-adhesive and highly attenuated double mutant (ΔeseJ_eiΔfimA_-245-_-50 strain) was constructed, and it was used as a vaccine candidate in yellow catfish via bath immersion at a dosage of 1 × 10⁵ CFU/mL. It was found that this vaccine candidate can stimulate protection when challenged with E. ictaluri HSN-1 at 5 × 10⁷ CFU/mL (∼20 × LD₅₀). The survival rate was 83.61% for the vaccinated group and 33.33% for the sham-vaccinated group. The RPS (relative percent of survival) of the vaccination trial reached 75.41%. In conclusion, the ΔeseJ_eiΔfimA_-245-_-50 strain developed in this study can be used as a vaccine candidate. It excels in terms of ease of delivery (via bath immersion) and is highly efficient in stimulating protection against E. ictaluri infection.

Innate Bacteriostatic Mechanisms Defend the Urinary Tract

Urinary tract infection (UTI) is the most common type of urogenital disease. UTI affects the urethra, bladder, ureter, and kidney. A total of 13.3% of women, 2.3% of men, and 3.4% of children in the United States will require treatment for UTI. Traditionally, bladder (cystitis) and kidney (pyelonephritis) infections are considered independently. However, both infections induce host defenses that are either shared or coordinated across the urinary tract. Here, we review the chemical and biophysical mechanisms of bacteriostasis, which limit the duration and severity of the illness. Urinary bacteria attempt to overcome each of these defenses, complicating description of the natural history of UTI.

Identification of Desmoglein-2 as a novel target of Helicobacter pylori HtrA in epithelial cells

BACKGROUND

High temperature requirement A (HtrA) is an active serine protease secreted by the group-I carcinogen Helicobacter pylori (H. pylori). The human cell adhesion protein and tumor suppressor E-cadherin (hCdh1) expressed on the surface of gastric epithelial cells was identified as the first HtrA substrate. HtrA-mediated hCdh1 cleavage and subsequent disruption of intercellular adhesions are considered as important steps in H. pylori pathogenesis. In this study, we performed a proteomic profiling of H. pylori HtrA (HpHtrA) to decipher the complex mechanism of H. pylori interference with the epithelial barrier integrity.

RESULTS

Using a proteomic approach we identified human desmoglein-2 (hDsg2), neuropilin-1, ephrin-B2, and semaphorin-4D as novel extracellular HpHtrA substrates and confirmed the well characterized target hCdh1. HpHtrA-mediated hDsg2 cleavage was further analyzed by in vitro cleavage assays using recombinant proteins. In infection experiments, we demonstrated hDsg2 shedding from H. pylori-colonized MKN28 and NCI-N87 cells independently of pathogen-induced matrix-metalloproteases or ADAM10 and ADAM17.

CONCLUSIONS

Characterizing the substrate specificity of HpHtrA revealed efficient hDsg2 cleavage underlining the importance of HpHtrA in opening intercellular junctions. Video Abstract.

Exploiting pilus-mediated bacteria-host interactions for health benefits

Surface pili (or fimbriae) are an important but conspicuous adaptation of several genera and species of Gram-negative and Gram-positive bacteria. These long and non-flagellar multi-subunit adhesins mediate the initial contact that a bacterium has with a host or environment, and thus have come to be regarded as a key colonization factor for virulence activity in pathogens or niche adaptation in commensals. Pili in pathogenic bacteria are well recognized for their roles in the adhesion to host cells, colonization of tissues, and establishment of infection. As an 'anti-adhesive' ploy, targeting pilus-mediated attachment for disruption has become a potentially effective alternative to using antibiotics. In this review, we give a description of the several structurally distinct bacterial pilus types thus far characterized, and as well offer details about the intricacy of their individual structure, assembly, and function. With a molecular understanding of pilus biogenesis and pilus-mediated host interactions also provided, we go on to describe some of the emerging new approaches and compounds that have been recently developed to prevent the adhesion, colonization, and infection of piliated bacterial pathogens.