Invasion processes of pathogenic Escherichia coli

Identification of Virulence Genes Associated with Pathogenicity of Translocating Escherichia coli with Special Reference to the Type 6 Secretion System

Recent genomic characterisation of translocating Escherichia coli HMLN-1 isolated from mesenteric lymph nodes (MLNs) and blood of a patient with a fatal case of pancreatitis revealed the presence of a type 6 secretion system (T6SS) that was not present in non-translocating E. coli strains. This strain was also genomically similar to adherent-invasive E. coli (AIEC) LF82 pathotype. We aimed to identify the role of T6SS-1 in the pathogenesis of this strain and other pathogenic E. coli. The HMLN-1 strain was initially tested for the presence of six virulence genes (VGs) associated with AIEC strains and an iron sequestering system. Additionally, HMLN-1's interaction with a co-culture of Caco-2:HT29-MTX cells and its intra-macrophagic survival was evaluated. We subsequently screened a collection of 319 pathogenic E. coli strains isolated from patients with urinary tract infection (UTI), diarrhoea, inflammatory bowel disease (IBD) and septicaemia for the presence of T6SS-1 and its expression related to adhesion, invasion and translocation via the above co-culture of the intestinal cell lines. The results showed that HMLN-1 harboured four of the AIEC-associated VGs (dsbA, htrA, ompC and afaC). Screening of the pathogenic E. coli collection detected the presence of the T6SS-1 genes in septicaemic and UTI E. coli strains at a significantly higher level than diarrhoea and IBD strains (p < 0.0001). The high expression of T6SS-1 in E. coli HMLN-1 upon adhesion and invasion, as well as its high prevalence among extra-intestinal E. coli strains, suggests a role for T6SS-1 in the pathogenesis of translocating E. coli.

The Cytotoxic Necrotizing Factors (CNFs)-A Family of Rho GTPase-Activating Bacterial Exotoxins

The cytotoxic necrotizing factors (CNFs) are a family of Rho GTPase-activating single-chain exotoxins that are produced by several Gram-negative pathogenic bacteria. Due to the pleiotropic activities of the targeted Rho GTPases, the CNFs trigger multiple signaling pathways and host cell processes with diverse functional consequences. They influence cytokinesis, tissue integrity, cell barriers, and cell death, as well as the induction of inflammatory and immune cell responses. This has an enormous influence on host-pathogen interactions and the severity of the infection. The present review provides a comprehensive insight into our current knowledge of the modular structure, cell entry mechanisms, and the mode of action of this class of toxins, and describes their influence on the cell, tissue/organ, and systems levels. In addition to their toxic functions, possibilities for their use as drug delivery tool and for therapeutic applications against important illnesses, including nervous system diseases and cancer, have also been identified and are discussed.

Prostate Microbiota and Prostate Cancer: A New Trend in Treatment

Although the incidence and mortality of prostate cancer have gradually begun to decline in the past few years, it is still one of the leading causes of death from malignant tumors in the world. The occurrence and development of prostate cancer are affected by race, family history, microenvironment, and other factors. In recent decades, more and more studies have confirmed that prostate microflora in the tumor microenvironment may play an important role in the occurrence, development, and prognosis of prostate cancer. Microorganisms or their metabolites may affect the occurrence and metastasis of cancer cells or regulate anti-cancer immune surveillance. In addition, the use of tumor microenvironment bacteria in interventional targeting therapy of tumors also shows a unique advantage. In this review, we introduce the pathway of microbiota into prostate cancer, focusing on the mechanism of microorganisms in tumorigenesis and development, as well as the prospect and significance of microorganisms as tumor biomarkers and tumor prevention and treatment.

Colibactin in avian pathogenic Escherichia coli contributes to the development of meningitis in a mouse model

Colibactin is synthesized by a 54-kb genomic island, leads to toxicity in eukaryotic cells, and plays a vital role in many diseases, including neonatal sepsis and meningitis. Avian pathogenic Escherichia coli (APEC) is speculated to be an armory of extraintestinal pathogenic Escherichia coli and can be a potential zoonotic bacterium that threatens human and animal health. In this study, the APEC XM meningitis mouse model was successfully established to investigate the effect of colibactin in in vivo infection. The clbH-deletion mutant strain induced lower γ-H2AX expression, no megalocytosis, and no cell cycle arrest in bEnd.3 cells, which showed that the deletion of clbH decreased the production of colibactin in the APEC XM strain. The deletion of clbH did not affect the APEC XM strain’s ability of adhering to and invading bEnd.3 cells. In vitro, the non-colibactin-producing strain displayed significantly lower serum resistance and it also induced a lower level of cytokine mRNA and few disruptions of tight junction proteins in infected bEnd.3 cells. Meningitis did not occur in APEC ΔclbH-infected mice in vivo, who showed fewer clinical symptoms and fewer lesions on radiological and histopathological analyses. Compared with the APEX XM strain, APEC ΔclbH induced lower bacterial colonization in tissues, lower mRNA expression of cytokines in brain tissues, and slight destruction of the brain blood barrier. These results indicate that clbH is a necessary component for the synthesis of genotoxic colibactin, and colibactin is related to the development of meningitis induced by APEC XM.

Escherichia coli Causing Neonatal Meningitis During 2001-2020: A Study in Eastern China

Background and Objective

Neonatal meningitis (NM) caused by Escherichia coli remains a major health problem in industrialized countries. Currently, information on the epidemiology and antimicrobial susceptibility patterns of NM in developing countries such as China is relatively scarce. Therefore, the present study investigated changes in the antimicrobial susceptibility of E. coli causing NM in a perinatal center in eastern China over the past 20 years.

Methods

This survey was conducted during three periods: 2001–2006, 2007–2012, and 2013–2020. NM was diagnosed according to the number of white blood cells in the cerebrospinal fluid (CSF) and the presence of a single potential pathogenic bacterium in the culture prepared from the blood or CSF of a newborn baby. Changes in the antimicrobial susceptibility of E. coli were analyzed.

Results

In total, 182 NM cases were identified. E. coli was identified in 69 of these cases, and in 21 of these cases, extended-spectrum beta-lactamase (ESBL) production was detected. E. coli was the main cause of NM identified in this study. The overall susceptibility of E. coli to third-generation cephalosporins such as cefotaxime decreased from 100% during 2001–2006 to 50% during 2007–2012 and, subsequently, increased to 71.0% during 2013–2020. This pattern of change is correlated with bacterial ESBL production. Only 8.3% of E. coli found in samples collected from infants with early onset meningitis (EOM) produced ESBL, while 37.3% of E. coli isolated from children with late-onset meningitis (LOM) produced ESBL.

Conclusion

E. coli remains the primary pathogen of NM. Compared with that isolated from infants with LOM, the percentage of ESBL-producing multidrug-resistant E. coli isolated from infants with EOM is significantly lower. Clinicians should consider this trend when determining appropriate and effective antibiotics as empirical treatment for NM.

Toll-interacting protein impacts on inflammation, autophagy, and vacuole trafficking in human disease

Toll-interacting protein (TOLLIP) is a ubiquitous intracellular adaptor protein involved in multiple intracellular signaling pathways. It plays a key role in mediating inflammatory intracellular responses, promoting autophagy, and enabling vacuole transport within the cell. TOLLIP is being increasingly recognized for its role in disease pathophysiology through involvement in these three primary pathways. Recent research also indicates that TOLLIP is involved in nuclear-cytoplasmic transfer, although this area requires further exploration. TOLLIP is involved in the pathophysiologic pathways associated with neurodegenerative diseases, pulmonary diseases, cardiovascular disease, inflammatory bowel disease, and malignancy. We postulate that TOLLIP plays an integral role in the disease pathophysiology of other conditions involved in vacuole trafficking and autophagy. We suggest that future research in this field should investigate the role of TOLLIP in the pathogenesis of these multiple conditions. This research has the potential to inform disease mechanisms and identify novel opportunities for therapeutic advances in multiple disease processes.

CNS Macrophages and Infant Infections

The central nervous system (CNS) harbors its own immune system composed of microglia in the parenchyma and CNS-associated macrophages (CAMs) in the perivascular space, leptomeninges, dura mater, and choroid plexus. Recent advances in understanding the CNS resident immune cells gave new insights into development, maturation and function of its immune guard. Microglia and CAMs undergo essential steps of differentiation and maturation triggered by environmental factors as well as intrinsic transcriptional programs throughout embryonic and postnatal development. These shaping steps allow the macrophages to adapt to their specific physiological function as first line of defense of the CNS and its interfaces. During infancy, the CNS might be targeted by a plethora of different pathogens which can cause severe tissue damage with potentially long reaching defects. Therefore, an efficient immune response of infant CNS macrophages is required even at these early stages to clear the infections but may also lead to detrimental consequences for the developing CNS. Here, we highlight the recent knowledge of the infant CNS immune system during embryonic and postnatal infections and the consequences for the developing CNS.

Transcriptome profiling of avian pathogenic Escherichia coli and the mouse microvascular endothelial cell line bEnd.3 during interaction

Background

Avian pathogenic Escherichia coli (APEC), an important extraintestinal pathogenic E. coli, causes colibacillosis, an acute and mostly systemic disease involving multiple organ lesions such as meningitis. Meningitis-causing APEC can invade the host central nervous system by crossing the blood–brain barrier (BBB), which is a critical step in the development of meningitis. However, the bacteria-host interaction mechanism in this process remains unclear.

Methods

In this study, we examined E. coli and bEnd.3 cells transcriptomes during infection and mock infection to investigate the global transcriptional changes in both organisms using RNA sequencing approach.

Results

When APEC infected the bEnd.3 cells, several significant changes in the expression of genes related to cell junctional complexes, extracellular matrix degradation, actin cytoskeleton rearrangement, immune activation and the inflammatory response in bEnd.3 cells were observed as compared to the mock infection group. Thus, the immune activation of bEnd.3 cells indicated that APEC infection activated host defenses. Furthermore, APEC may exploit cell junction degradation to invade the BBB. In addition, amino acid metabolism and energy metabolism related genes were downregulated and the protein export pathway related genes were upregulated in APEC cultured with bEnd.3 cells, compared to that in control. Thus, APEC may encounter starvation and express virulence factors during incubation with bEnd.3 cells.

Conclusion

This study provides a comprehensive overview of transcriptomic changes that occur during APEC infection of bEnd.3 cells, and offers insights into the bacterial invasion strategies and the subsequent host defense mechanism.

Transactivated Epidermal Growth Factor Receptor Recruitment of α-actinin-4 From F-actin Contributes to Invasion of Brain Microvascular Endothelial Cells by Meningitic Escherichia coli

Bacterial penetration of the blood-brain barrier requires its successful invasion of brain microvascular endothelial cells (BMECs), and host actin cytoskeleton rearrangement in these cells is a key prerequisite for this process. We have reported previously that meningitic Escherichia coli can induce the activation of host's epidermal growth factor receptor (EGFR) to facilitate its invasion of BMECs. However, it is unknown how EGFR specifically functions during this invasion process. Here, we identified an important EGFR-interacting protein, α-actinin-4 (ACTN4), which is involved in maintaining and regulating the actin cytoskeleton. We observed that transactivated-EGFR competitively recruited ACTN4 from intracellular F-actin fibers to disrupt the cytoskeleton, thus facilitating bacterial invasion of BMECs. Strikingly, this mechanism operated not only for meningitic E. coli, but also for infections with Streptococcus suis, a Gram-positive meningitis-causing bacterial pathogen, thus revealing a common mechanism hijacked by these meningitic pathogens where EGFR competitively recruits ACTN4. Ever rising levels of antibiotic-resistant bacteria and the emergence of their extended-spectrum antimicrobial-resistant counterparts remind us that EGFR could act as an alternative non-antibiotic target to better prevent and control bacterial meningitis.

Interorgan Molecular Communication Strategies of "Local" and "Systemic" Innate Immune Responses in Mosquito Anopheles stephensi

Mosquitoes that transmit many deadly infectious diseases also need to keep fighting against many microbial infections. Constitutive expression of multiple antimicrobial peptides (AMPs) in almost all body tissues is believed to facilitate the effective management of these local infections. When any infection breaches the local barrier, AMPs are induced rapidly in non-target tissues such as hemocytes (HCs) and establish their co-ordination with systemic immune effectors to clear off the body infection. But how interorgan immune communication is managed during local and systemic infections remain largely unknown. To understand this interorgan molecular relationship, we identified, extensively profiled and compared the expression of AMPs in three important mosquito tissues viz. midgut, fat body (FB), and HCs. dsRNA-mediated AMPs silencing suggests that mosquito tissues are able to manage an optimal expression of AMPs at the physiological level. We also examined the possible contribution of two important immune regulator genes relish (REL) and nitric oxide synthase, controlling AMPs expression in these tissues during local or systemic infections. We show that each tissue has a unique ability to respond to local/systemic challenges, but HCs are more specialized to recognize and discriminate-specific antigens than gut and FB. Our investigation also revealed that both REL and NO participate in the overall management of the interorgan immune responses, but at the same time each tissue also has its own ability to maintain the interorgan flow of signals. In our knowledge, this is the first large-scale study examining the interorgan immune relationship in the mosquito.

Human Meningitis-Associated Escherichia coli

Escherichia coli is the most common Gram-negative bacillary organism causing meningitis, and E. coli meningitis continues to be an important cause of mortality and morbidity throughout the world. Our incomplete knowledge of its pathogenesis contributes to such mortality and morbidity. Recent reports of E. coli strains producing CTX-M-type or TEM-type extended-spectrum β-lactamases create a challenge. Studies using in vitro and in vivo models of the blood-brain barrier have shown that E. coli meningitis follows a high degree of bacteremia and invasion of the blood-brain barrier. E. coli invasion of the blood-brain barrier, the essential step in the development of E. coli meningitis, requires specific microbial and host factors as well as microbe- and host-specific signaling molecules. Blockade of such microbial and host factors contributing to E. coli invasion of the blood-brain barrier is shown to be efficient in preventing E. coli penetration into the brain. The basis for requiring a high degree of bacteremia for E. coli penetration of the blood-brain barrier, however, remains unclear. Continued investigation on the microbial and host factors contributing to a high degree of bacteremia and E. coli invasion of the blood-brain barrier is likely to identify new targets for prevention and therapy of E. coli meningitis.

Outbreak Caused by Escherichia coli O18: K1: H7 Sequence Type 95 in a Neonatal Intensive Care Unit in Barcelona, Spain

BACKGROUND

Escherichia coli is one of the most frequent causes of late-onset neonatal sepsis. The aim of this study was to characterize an outbreak of neonatal sepsis occurring in the neonatal intensive care unit of the Hospital Clinic of Barcelona from April to August 2013.

METHODS

After presentation of the index case, all E. coli isolates from previously hospitalized neonates, health-care workers and neonates admitted to the neonatal intensive care unit from April to October 2013 were tested for K1 antigen positivity and epidemiologically compared by pulse-field gel electrophoresis. Furthermore, the E. coli K1 strains collected from neonates during this period were analyzed by different methods (serotyping, phylotyping, polymerase chain reaction of virulence factors, antimicrobial resistance and "in vitro" assays in Human Brain Microvascular Endothelial Cells (HBMEC)).

RESULTS

An E. coli O18:K1:H7 sequence type 95 and phylogenetic group B2 strain was the cause of the outbreak involving 6 preterm neonates: 1 with late septicemia because of a urinary focus and 5 with late-onset septicemia and meningitis, 3 of whom died. All showed the same pulsotype, full resistance to ampicillin and intermediate resistance to gentamicin. The outbreak strain carried the pathogenicity island (PAI) IIJ96-like domain that could explain the high-grade bacteremia necessary to develop meningitis.

CONCLUSIONS

All the E. coli isolates responsible for this outbreak belonged to a single clone suggesting a common source of infection, and it was categorized as O18:K1:H7. Despite the bacteria's pathogenicity has an important role in the severity of infection, the host-associated factors were crucial for the fatal outcomes.

Bacterium-Derived Cell-Penetrating Peptides Deliver Gentamicin To Kill Intracellular Pathogens

Commonly used antimicrobials show poor cellular uptake and often have limited access to intracellular targets, resulting in low antimicrobial activity against intracellular pathogens. An efficient delivery system to transport these drugs to the intracellular site of action is needed. Cell-penetrating peptides (CPPs) mediate the internalization of biologically active molecules into the cytoplasm. Here, we characterized two CPPs, α1H and α2H, derived from the Yersinia enterocolitica YopM effector protein. These CPPs, as well as Tat (trans-activator of transcription) from HIV-1, were used to deliver the antibiotic gentamicin to target intracellular bacteria. The YopM-derived CPPs penetrated different endothelial and epithelial cells to the same extent as Tat. CPPs were covalently conjugated to gentamicin, and CPP-gentamicin conjugates were used to target infected cells to kill multiple intracellular Gram-negative pathogenic bacteria, including Escherichia coli K1, Salmonella enterica serovar Typhimurium, and Shigella flexneri Taken together, CPPs show great potential as delivery vehicles for antimicrobial agents and may contribute to the generation of new therapeutic tools to treat infectious diseases caused by intracellular pathogens.

Vimentin, a Novel NF-κB Regulator, Is Required for Meningitic Escherichia coli K1-Induced Pathogen Invasion and PMN Transmigration across the Blood-Brain Barrier

BACKGROUND

NF-κB activation, pathogen invasion, polymorphonuclear leukocytes (PMN) transmigration (PMNT) across the blood-brain barrier (BBB) are the pathogenic triad hallmark features of bacterial meningitis, but the mechanisms underlying these events remain largely unknown. Vimentin, which is a novel NF-κB regulator, is the primary receptor for the major Escherichia coli K1 virulence factor IbeA that contributes to the pathogenesis of neonatal bacterial sepsis and meningitis (NSM). We have previously shown that IbeA-induced NF-κB signaling through its primary receptor vimentin as well as its co-receptor PTB-associated splicing factor (PSF) is required for pathogen penetration and leukocyte transmigration across the BBB. This is the first in vivo study to demonstrate how vimentin and related factors contributed to the pathogenic triad of bacterial meningitis.

METHODOLOGY/PRINCIPAL FINDINGS

The role of vimentin in IbeA+ E. coli K1-induced NF-κB activation, pathogen invasion, leukocyte transmigration across the BBB has now been demonstrated by using vimentin knockout (KO) mice. In the in vivo studies presented here, IbeA-induced NF-κB activation, E. coli K1 invasion and polymorphonuclear neutrophil (PMN) transmigration across the BBB were significantly reduced in Vim-/- mice. Decreased neuronal injury in the hippocampal dentate gyrus was observed in Vim-/- mice with meningitis. The major inflammatory regulator α7 nAChR and several signaling molecules contributing to NF-κB activation (p65 and p-CamKII) were significantly reduced in the brain tissues of the Vim-/- mice with E. coli meningitis. Furthermore, Vim KO resulted in significant reduction in neuronal injury and in α7 nAChR-mediated calcium signaling.

CONCLUSION/SIGNIFICANCE

Vimentin, a novel NF-κB regulator, plays a detrimental role in the host defense against meningitic infection by modulating the NF-κB signaling pathway to increase pathogen invasion, PMN recruitment, BBB permeability and neuronal inflammation. Our findings provide the first evidence for Vim-dependent mechanisms underlying the pathogenic triad of bacterial meningitis.

Bacteremia in Early Infancy: Etiology and Management

We reviewed the literature regarding bacteremia in early infancy (age ≤ 90 days). Bacteremia remains a major cause of morbidity and mortality in young infants. However, recent epidemiologic data suggest that the incidence of bacteremia is decreasing and the pathogens responsible for invasive disease are changing. These changes will impact the evaluation and management of young infants. We review the current epidemiology of community-acquired bacteremia in early infancy with particular emphasis on the causative agents, diagnostic evaluation, and empiric and definitive antimicrobial treatment.

The choroid plexus-a multi-role player during infectious diseases of the CNS

The choroid plexus (CP) is the source of cerebrospinal fluid (CSF) production and location of the blood-CSF barrier (BCSFB), which is constituted by the epithelial cells of the CP. Several infectious pathogens including viruses, bacteria, fungi and parasites cross the BCSFB to enter the central nervous system (CNS), ultimately leading to inflammatory infectious diseases like meningitis and meningoencephalitis. The CP responds to this challenge by the production of chemokines and cytokines as well as alterations of the barrier function of the BCSFB. During the course of CNS infectious disease host immune cells enter the CNS, eventually contributing to the cellular damage caused by the disease. Additional complications, which are in certain cases caused by choroid plexitis, can arise due to the response of the CP to the pathogens. In this review we will give an overview on the multiple functions of the CP during brain infections highlighting the CP as a multi-role player during infectious diseases of the CNS. In this context the importance of tools for investigation of these CP functions and a possible suitability of the CP as therapeutic target will be discussed.

Two plasmid-encoded genes of enteropathogenic Escherichia coli strain K798 promote invasion and survival within HEp-2 cells

Enteropathogenic Escherichia coli (EPEC) are considered to be extracellular pathogens, inducing attaching and effacing lesions following their attachment to the surface of eukaryotic cells; however, in vitro and in vivo invasion by EPEC has been reported in several studies. A cloned 4.6 kb fragment of EPEC plasmid pLV501 has been shown to facilitate invasion of E. coli K-12, and here we further investigate the nature of this process. Two of the three complete open reading frames contained within the plasmid fragment have been cloned to E. coli, and in HEp-2 adherence assays both tniA2 and pecM were shown to be expressed during the first 3 h of infection from a plac promoter. Escherichia coli transformants carrying pecM alone or in combination with tniA2 were able to both survive intracellularly and escape eukaryotic cells to re-establish themselves within the medium, whereas those bacterial cells carrying tniA2 alone could not be isolated from within HEp-2 cells after 24 h of infection, but were present in the previously sterile medium surrounding the cells. Bacteria carrying pecM and tniA2 adhered to HEp-2 cells with sites of adhesion characterized by underlying actin polymerization. The invasive potential conferred by these genes may give EPEC strains a survival advantage during prolonged infection.

Frequent combination of antimicrobial multiresistance and extraintestinal pathogenicity in Escherichia coli isolates from urban rats (Rattus norvegicus) in Berlin, Germany

Urban rats present a global public health concern as they are considered a reservoir and vector of zoonotic pathogens, including Escherichia coli. In view of the increasing emergence of antimicrobial resistant E. coli strains and the on-going discussion about environmental reservoirs, we intended to analyse whether urban rats might be a potential source of putatively zoonotic E. coli combining resistance and virulence. For that, we took fecal samples from 87 brown rats (Rattus norvegicus) and tested at least three E. coli colonies from each animal. Thirty two of these E. coli strains were pre-selected from a total of 211 non-duplicate isolates based on their phenotypic resistance to at least three antimicrobial classes, thus fulfilling the definition of multiresistance. As determined by multilocus sequence typing (MLST), these 32 strains belonged to 24 different sequence types (STs), indicating a high phylogenetic diversity. We identified STs, which frequently occur among extraintestinal pathogenic E. coli (ExPEC), such as STs 95, 131, 70, 428, and 127. Also, the detection of a number of typical virulence genes confirmed that the rats tested carried ExPEC-like strains. In particular, the finding of an Extended-spectrum beta-lactamase (ESBL)-producing strain which belongs to a highly virulent, so far mainly human- and avian-restricted ExPEC lineage (ST95), which expresses a serogroup linked with invasive strains (O18:NM:K1), and finally, which produces an ESBL-type frequently identified among human strains (CTX-M-9), pointed towards the important role, urban rats might play in the transmission of multiresistant and virulent E. coli strains. Indeed, using a chicken infection model, this strain showed a high in vivo pathogenicity. Imagining the high numbers of urban rats living worldwide, the way to the transmission of putatively zoonotic, multiresistant, and virulent strains might not be far ahead. The unforeseeable consequences of such an emerging public health threat need careful consideration in the future.

Effects of bacterial toxins on endothelial tight junction in vitro: a mechanism-based investigation

ABSTRACT Lipopolysaccharide (LPS) and lipoteichoic acid (LTA), principal cell wall components of Gram-negative and Gram-positive bacteria, respectively, play a central role in altering the blood-brain barrier and facilitate bacterial infection of the host brain. Despite the significance of bacterial toxins in disease pathogenesis, mechanisms by which toxins impair the barrier are not yet known. This study, using an in vitro cell culture model, showed that LPS and LTA interacted with the endothelial cells and disrupted the tight junction between the cells that increased the barrier's permeability. Both toxins increased inducible nitric oxide synthase (iNOS) mRNA that is indicative of an increase in intracellular NO release, disrupted architecture of the tight junction proteins, suppressed zonula occludens-1 (ZO-1) and occludin (OCL) and junctional adhesive molecules (JAM) mRNA levels, and increased tumor necrosis factor alpha (TNFalpha) and interleukin-1 beta (IL-1beta) mRNA levels. Anti-CD14 antibodies blocked the increase in TNFalpha and IL-1beta mRNA levels but did not affect either changes in the tight junction or iNOS, ZO-1, OCL, and JAM mRNA levels in endothelial cells and astrocytes. Although both toxins did not cross the endothelial barrier, the abluminal neurons exhibited high inflammatory activity characterized by a sequential increase in TNFalpha, IL-1beta, external receptor kinase (ERK), and RelA-p50 that induced inflammation, followed by an increase in anti-inflammatory/apoptotic factors including IL-10 and cysteine-aspartic acid protease-8 (CASPASE-8), which resolve inflammation and induce apoptosis. Anti-CD14 antibodies in luminal buffer blocked the pro- and anti-inflammatory effects of the toxins in neurons. Thus, the CD14-TLR cascade that participates in the inflammatory effects of toxins may not participate in the toxin-induced barrier disruption in vitro. Since the toxins did not cross the endothelial barrier, induction of inflammation in neurons was due to a release of proinflammatory cytokines in the abluminal fluid.

Infections of the nervous system

Glycemic control is an important aspect of patient care in the surgical Infections of the nervous system are among the most difficult infections in terms of the morbidity and mortality posed to patients, and thereby require urgent and accurate diagnosis. Although viral meningitides are more common, it is the bacterial meningitides that have the potential to cause a rapidly deteriorating condition that the physician should be familiar with. Viral encephalitis frequently accompanies viral meningitis, and can produce focal neurologic findings and cognitive difficulties that can mimic other neurologic disorders. Brain abscesses also have the potential to mimic and present like other neurologic disorders, and cause more focal deficits. Finally, other infectious diseases of the central nervous system, such as prion disease and cavernous sinus thrombosis, are explored in this review.

NlpI facilitates deposition of C4bp on Escherichia coli by blocking classical complement-mediated killing, which results in high-level bacteremia

Neonatal meningitis Escherichia coli (NMEC) is the most common Gram-negative organism that is associated with neonatal meningitis, which usually develops as a result of hematogenous spread of the bacteria. There are two key pathogenesis processes for NMEC to penetrate into the brain, the essential step for the development of E. coli meningitis: a high-level bacteremia and traversal of the blood-brain barrier (BBB). Our previous study has shown that the bacterial outer membrane protein NlpI contributes to NMEC binding to and invasion of brain microvascular endothelial cells, the major component cells of the BBB, suggesting a role for NlpI in NMEC crossing of the BBB. In this study, we showed that NlpI is involved in inducing a high level of bacteremia. In addition, NlpI contributed to the recruitment of the complement regulator C4bp to the surface of NMEC to evade serum killing, which is mediated by the classical complement pathway. NlpI may be involved in the interaction between C4bp and OmpA, which is an outer membrane protein that directly interacts with C4bp on the bacterial surface. The involvement of NlpI in two key pathogenesis processes of NMEC meningitis may make this bacterial factor a potential target for prevention and therapy of E. coli meningitis.

Both host and pathogen factors predispose to Escherichia coli urinary-source bacteremia in hospitalized patients

BACKGROUND

The urinary tract is the most common source for Escherichia coli bacteremia. Mortality from E. coli urinary-source bacteremia is higher than that from urinary tract infection. Predisposing factors for urinary-source E. coli bacteremia are poorly characterized.

METHODS

In order to identify urinary-source bacteremia risk factors, we conducted a 12-month prospective cohort study of adult inpatients with E. coli bacteriuria that were tested for bacteremia within ±1 day of the bacteriuria. Patients with bacteremia were compared with those without bacteremia. Bacterial isolates from urine were screened for 16 putative virulence genes using high-throughput dot-blot hybridization.

RESULTS

Twenty-four of 156 subjects (15%) had E. coli bacteremia. Bacteremic patients were more likely to have benign prostatic hyperplasia (56% vs 19%; P = .04), a history of urogenital surgery (63% vs 28%; P = .001), and presentation with hesitancy/retention (21% vs 4%; P = .002), fever (63% vs 38%; P = .02), and pyelonephritis (67% vs 41%; P = .02). The genes kpsMT (group II capsule) (17 [71%] vs 62 [47%]; P = .03) and prf (P-fimbriae family) (13 [54%] vs 40 [30%]; P = .02) were more frequent in the urinary strains from bacteremic patients. Symptoms of hesitancy/retention (odds ratio [OR], 7.8; 95% confidence interval [CI], 1.6-37), history of a urogenital procedure (OR, 5.4; 95% CI, 2-14.7), and presence of kpsMT (OR, 2.9; 95% CI, 1-8.2) independently predicted bacteremia.

CONCLUSIONS

Bacteremia secondary to E. coli bacteriuria was frequent (15%) in those tested for it. Urinary stasis, surgical disruption of urogenital tissues, and a bacterial capsule characteristic contribute to systemic invasion by uropathogenic E. coli.

Polyphosphate kinase 1 is required for the pathogenesis process of meningitic Escherichia coli K1 (RS218)

Aim: Polyphosphate kinase 1 (PPK1), encoded by the ppk1 gene, is one of the major enzymes to reversibly catalyze the synthesis of polyphosphate (poly P) from the terminal phosphate of ATP. Poly P confers resistance to stress in a number of bacterial species but its role in the virulence of meningitic bacterial pathogens is unknown. The aim of this study was to determine the role of PPK1 in the pathogenesis of Escherichia coli meningitis. Materials & methods: An isogenic in-frame ppk1 deletion mutant (PD44) of E. coli K1 strain E44 was constructed and characterized. Human brain microvascular endothelial cells and neonatal rats were used as the in vitro and in vivo models, respectively, to evaluate bacterial adhesion/invasion and the abilities of bacteria crossing the blood–brain barrier (BBB) to cause meningitis. The survival of PD44 and E44 under osmotic and acid stress conditions were also examined. Results: Poly P levels in E44 were clearly higher than those in PD44, especially at the stationary phase (SP). The ppk1 deletion mutant PD44 also showed poor survival rates during osmotic shock and acidic challenge, which the bacteria would face during pathogenesis. In vitro and in vivo assays revealed that PD44 was defective in bacterial adhesion and translocation across the BBB. By using the Evans blue method, we found that E44-induced permeability of the BBB in neonatal rats was significantly higher than that of the animals infected with PD44. Cytokine ELISA results showed that the TNF-α and IL-1β levels in the serum and brain tissues of the neonatal rats infected with PD44 were lower than that of the E44 group. A more obvious meningeal inflammation could be observed in the brain tissues of the rats infected with E44 when compared with that of the PD44 group by histopathological examination. Furthermore, the mRNA expression of IbeR, which is an RpoS-like regulator contributing to the SP regulation in E44, was found to be decreased in PD44 when compared with the parent strain. PD44 was also deficient in mRNA expression of the invasin IbeA, the adhesin FimH and the outer member protein A, which contributes to E44 penetration across BBB and resistance to the stimulations of low pH and high osmolarity. Conclusion: These results indicate that ppk1 plays an important role in stress adaption and virulence in meningitic E. coli K1 strain E44, and controls the relevant phenotypes by modulating the expression of the SP regulatory gene ibeR and the virulence genes ibeA, fimH and ompA.

Vascular endothelial growth factor receptor 1 contributes to Escherichia coli K1 invasion of human brain microvascular endothelial cells through the phosphatidylinositol 3-kinase/Akt signaling pathway

Escherichia coli is the most common Gram-negative organism causing neonatal meningitis. Previous studies demonstrated that E. coli K1 invasion of brain microvascular endothelial cells (BMEC) is required for penetration into the central nervous system, but the microbe-host interactions that are involved in this process remain incompletely understood. Here we report the involvement of vascular endothelial growth factor receptor 1 (VEGFR1) expressed on human brain microvascular endothelial cells (HBMEC) in E. coli K1 invasion of HBMEC. Our results showed that treatment of confluent HBMEC with pan-VEGFR inhibitors significantly inhibited E. coli K1 invasion of HBMEC. Immunofluorescence results indicated the colocalization of VEGFR1 with E. coli K1 during bacterial invasion of HBMEC. The E. coli-induced actin cytoskeleton rearrangements in HBMEC were blocked by VEGFR inhibitors but not by VEGFR2-specific inhibitors. The small interfering RNA (siRNA) knockdown of VEGFR1 in HBMEC significantly attenuated E. coli invasion and the concomitant actin filament rearrangement. Furthermore, we found an increased association of VEGFR1 with the p85 subunit of phosphatidylinositol 3-kinase (PI3K) in HBMEC infected with E. coli K1 and that E. coli K1-triggered Akt activation in HBMEC was blocked by VEGFR1 siRNA and VEGFR inhibitors. Taken together, our results demonstrate that VEGFR1 contributes to E. coli K1 invasion of HBMEC via recruitment of the PI3K/Akt signaling pathway.

NlpI contributes to Escherichia coli K1 strain RS218 interaction with human brain microvascular endothelial cells

Escherichia coli K1 is the most common Gram-negative bacillary organism causing neonatal meningitis. E. coli K1 binding to and invasion of human brain microvascular endothelial cells (HBMECs) is a prerequisite for its traversal of the blood-brain barrier (BBB) and penetration into the brain. In the present study, we identified NlpI as a novel bacterial determinant contributing to E. coli K1 interaction with HBMECs. The deletion of nlpI did not affect the expression of the known bacterial determinants involved in E. coli K1-HBMEC interaction, such as type 1 fimbriae, flagella, and OmpA, and the contribution of NlpI to HBMECs binding and invasion was independent of those bacterial determinants. Previous reports have shown that the nlpI mutant of E. coli K-12 exhibits growth defect at 42 degrees C at low osmolarity, and its thermosensitive phenotype can be suppressed by a mutation on the spr gene. The nlpI mutant of strain RS218 exhibited similar thermosensitive phenotype, but additional spr mutation did not restore the ability of the nlpI mutant to interact with HBMECs. These findings suggest the decreased ability of the nlpI mutant to interact with HBMECs is not associated with the thermosensitive phenotype. NlpI was determined as an outer membrane-anchored protein in E. coli, and the nlpI mutant was defective in cytosolic phospholipase A(2)alpha (cPLA(2)alpha) phosphorylation compared to the parent strain. These findings illustrate the first demonstration of NlpI's contribution to E. coli K1 binding to and invasion of HBMECs, and its contribution is likely to involve cPLA(2)alpha.

Nitric oxide/cGMP signalling induces Escherichia coli K1 receptor expression and modulates the permeability in human brain endothelial cell monolayers during invasion

Escherichia coli K1 invasion of human brain microvascular endothelial cells (HBMEC) mediated by outer membrane protein A (OmpA) results in the leakage of HBMEC monolayers. Despite the influence of nitric oxide (NO) in endothelial cell tight junction integrity, its role in E. coli-induced HBMEC monolayer permeability is poorly defined. Here, we demonstrate that E. coli invasion of HBMEC stimulates NO production by increasing the inducible nitric oxide synthase (iNOS) expression. Exposure to NO-producing agents enhanced the invasion of OmpA(+)E. coli and thereby increased the permeability of HBMEC. OmpA(+)E. coli-induced NO production lead to increased generation of cGMP and triggered the expression of OmpA receptor, Ec-gp96 in HBMEC. Pre-treatment of HBMEC with iNOS inhibitors or by introducing siRNA to iNOS, but not to eNOS or cGMP inhibitors abrogated the E. coli-induced expression of Ec-gp96. Overexpression of the C-terminal truncated Ec-gp96 in HBMEC prevented NO production and its downstream effector, cGMP generation and consequently, the invasion of OmpA(+)E. coli. NO/cGMP production also activates PKC-alpha, which is previously shown to be involved in HBMEC monolayer leakage. These results indicate that NO/cGMP signalling pathway plays a novel role in OmpA(+)E. coli invasion of HBMEC by enhancing the surface expression of Ec-gp96.

[A serious and unexpected infectious complication after transrectal prostate biopsy]

Serious infectious complications may appear after a surgical procedure despite antimicrobial prophylaxis. We report a case of Escherichia Coli meningitis after a prostate puncture biopsy. Many factors may have contributed to this rare complication such as fluoroquinolone resistance, and/or the bacterium's ability to cross the brain blood barrier. The patient was not found susceptible to severe infections.

Enterobacter sakazakii enhances epithelial cell injury by inducing apoptosis in a rat model of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is an inflammatory intestinal disorder that affects 2%-5% of all premature infants. Enterobacter sakazakii, a common contaminant of milk-based powdered infant formula, has been implicated as a causative agent of sepsis, meningitis, and NEC in newborn infants, with high mortality rates. However, the role played by E. sakazakii in the pathogenesis of NEC is, to date, not known. Here, we demonstrate for the first time that E. sakazakii can induce clinical and histological NEC in newborn rats. E. sakazakii was found to bind to enterocytes in rat pups at the tips of villi and to intestinal epithelial cells (IEC-6) in culture, with no significant invasion. Exposure to E. sakazakii induced apoptosis and increased the production of interleukin-6 in IEC-6 cells and in the animal model. These data suggest that E. sakazakii could be a potential pathogen that induces NEC and triggers intestinal disease by modulating enterocyte intracellular signaling pathways.

Differential expression of the polysialyl capsule during blood-to-brain transit of neuropathogenic Escherichia coli K1

Escherichia coli K1 isolates synthesize a polysialic acid (polySia) capsule, are components of the adult gastrointestinal microbiota and may cause lethal bacteraemia and meningitis if acquired maternally by newborn infants. We used a neonatal rat pup K1 infection model to establish that prompt administration of a selective capsule depolymerase reverses the bacteraemic state and prevents death of almost all pups. In untreated animals, bacteria colonize the gastrointestinal tract and gain entry to the blood compartment, where they express the non-O-acetylated form of polySia. The bacteria invade the major organs of the host; histological and histochemical analysis of brain sections revealed that at least some bacteria enter the central nervous system through the blood-cerebrospinal fluid barrier at the choroid plexus prior to colonization of the meninges. Once in this location, they cease expression of polySia. The unexpected abrogation of polySia, a factor associated with the pathogenesis of meningitis and essential for transit through the blood, suggests that the neuropathogen dispenses with its protective capsule once it has colonized protected niches. Thus, systemic infections due to encapsulated pathogens may be resolved by capsule depolymerization only if the enzyme modifies the bacteria whilst they are in the blood compartment.

Association between mortality of Escherichia coli meningitis in young infants and non-virulent clonal groups of strains

To identify factors associated with Escherichia coli meningitis (ECM) mortality in infants aged <3 months, the clinical, biological and bacterial characteristics of isolates from 99 cases of ECM were compared, including the phylogenetic group, multilocus sequence type, O serogroup and sequence O type (a combination of sequence type complex (STc) and O serogroup) and virulence genotype. All 99 isolates were susceptible to the initial antimicrobial treatment. The mortality rate (14%) was not influenced by term or post-natal age. Hypotension or seizures were the sole clinical predictive factors for fatal outcome (p <0.01), and abnormal initial trans-fontanellar ultrasound was associated with death (p 0.03). Seventy-seven isolates belonged to the common sequence O types (STc29(O1), STc29(O18), STc29(O45), STc301(O7), STc304(O16), STc697(O83), STc700(O1)) causing neonatal meningitis. None of the phylogenetic groups and none of the virulence determinants were distributed differently between survivors and non-survivors, except that the aerobactin gene (iucC) was less frequent in lethal isolates (94% vs. 71%, p 0.02). Isolates belonging to rare sequence O types were more likely to be lethal (OR 4.3, p 0.01), although they induced a lower level of bacteraemia than common sequence O types such as STc29(O18) and STc29(O45) in a neonatal rat model. These results suggest that unidentified human genetic risk-factors may be more important than strain virulence in predicting ECM mortality.

New biomarkers in an acute model of live Escherichia coli-induced sepsis in pigs

We developed a live Escherichia coli model of acute sepsis in pigs with emphasize on biomarkers reflecting the early inflammatory response of sepsis. Healthy pigs, 25-35 kg, were challenged intravenously (IV) (n = 12) or intrapulmonary (n = 6) with live E. coli and observed for 3 and 5 h respectively. Control pigs received culture medium (n = 6 + 3). Haemodynamic parameters and a broad panel of inflammatory mediators were measured. The dose of bacteria was carefully titrated to obtain a condition resembling the early phase of human septic shock. The IV group displayed a pro-inflammatory response [significant increase in tumour necrosis factor-alpha, interleukin (IL)-6 and IL-8] and an early anti-inflammatory response (significant increase in IL-10). For the first time, we demonstrate a significant increase in IL-12 and matrix metalloproteinase-9 (MMP) early in pig sepsis. Coagulation was activated (significant increase in thrombin-antithrombin complexes) and there was a significant decrease in the serum proteins suggesting capillary leakage. Haemodynamic parameters reflected a septic condition with significant decrease in systemic blood pressure, increases in heart rate, pulmonary artery pressure and base deficit. None of these changes was observed in the control group. Interleukin-1beta and vascular endothelial growth factor increased in both groups. Nitric oxide measurements suggested an initial pulmonary vascular endothelial inflammatory response. The intrapulmonary group, which did not resemble septic condition, showed a substantial increase in MMP-9. In this porcine model of sepsis, IL-12 and MMP-9 were detected for the first time. These biomarkers may have an impact in the understanding and future treatment of sepsis.

Involvement of Escherichia coli K1 ibeT in bacterial adhesion that is associated with the entry into human brain microvascular endothelial cells

IbeT is a downstream gene of the invasion determinant ibeA in the chromosome of a clinical isolate of Escherichia coli K1 strain RS218 (serotype 018:K1:H7). Both ibeT and ibeA are in the same operon. Our previous mutagenesis and complementation studies suggested that ibeT may coordinately contribute to E. coli K1 invasion with ibeA. An isogenic in-frame deletion mutant of ibeT has been made by chromosomal gene replacement with a recombinant suicide vector carrying a fragment with an ibeT internal deletion. The characteristics of the mutant in meningitic E. coli infection were examined in vitro [cell culture of human brain microvascular endothelial cells (HBMEC)] and in vivo (infant rat model of E. coli meningitis) in comparison with the parent strain. The ibeT deletion mutant was significantly less adhesive and invasive than its parent strain E. coli E44 in vitro, and the adhesion- and invasion-deficient phenotypes of the mutant can be complemented by the ibeT gene. Recombinant IbeT protein is able to block E. coli E44 invasion of HBMEC. Furthermore, the ibeT deletion mutant is less capable of colonizing intestine and less virulent in bacterial translocation across the blood-brain barrier (BBB) than its parent E. coli E44 in vivo. These data suggest that ibeT-mediated E. coli K1 adhesion is associated with the bacterial invasion process.

Going for baroque at the Escherichia coli K1 cell surface

Phase variation is usually thought of as the stochastic switching between alternatively expressed ('on') and unexpressed ('off') phenotypic states. However, coupling synthesis of a monotonous homopolysaccharide to a mechanism of random but incomplete chemical modification produces almost infinite structural variation. Potentially limitless variability implies that evolution can produce highly ornate or extravagant flourishes reminiscent of the baroque style. Here, we describe an analysis of capsular polysialic acid form variation in Escherichia coli K1, demonstrating that the large number of variant structures is controlled by a single contingency locus. The mechanism for generating maximum structural diversity from maximal genetic parsimony is conferred by a simple translational switch carried on a K1-specific prophage.

An enzymatic bionanotransduction system for multianalyte biological detection

AIM

The aim of this study was to develop and optimize a system for the detection of multiple biological targets in a single sample based on enzymatic bionanotransduction.

METHOD AND RESULTS

We used biological recognition elements (antibodies, DNA sequences) linked to DNA templates with T7 promoter regions for detection of specific target molecules. In vitro transcription of DNA templates bound to target molecules produced RNA nanosignals specific for every target in the sample. An enzyme-linked oligonucleotide fluorescence assay (ELOFA) provided a correlation between nanosignal profiles and target concentrations. The system was capable of detecting and distinguishing three species of specific immunoglobulin G (IgG) molecules at a level of 0.2 ng, mixed protein and DNA targets and single sample detection of Escherichia coli O157 micro-organisms and Staphylococcal enterotoxin B (SEB).

CONCLUSIONS

This report provided proof of concept for the use of enzymatic bionanotransduction with multianalyte biological detection based on differential nanosignal hybridization along with the application of this system to pathogen/toxin detection.

SIGNIFICANCE AND IMPACT OF THE STUDY

This system has the potential to be used as a tool for detection of multiple foodborne and environmental pathogens, toxins and targets of interest in a single sample.

Endothelial cell infection and hemostasis

As an important component of the vasculature, endothelial cell lining covers the inner surface of blood vessels and provides an active barrier interface between the vascular and perivascular compartments. In addition to maintaining vasomotor equilibrium and organ homeostasis and communicating with circulating blood cells, the vascular endothelium also serves as the preferred target for a number of infectious agents. This review article focuses on the roles of interactions between vascular endothelial cells and invading pathogens and resultant endothelial activation in the pathogenesis of important human diseases with viral and bacterial etiologies. In this perspective, the signal transduction events that regulate vascular inflammation and basis for endothelial cell tropism exhibited by certain specific viruses and pathogenic bacteria are also discussed.

Microbial translocation of the blood–brain barrier

A major contributing factor to high mortality and morbidity associated with CNS infection is the incomplete understanding of the pathogenesis of this disease. Relatively small numbers of pathogens account for most cases of CNS infections in humans, but it is unclear how such pathogens cross the blood-brain barrier (BBB) and cause infections. The development of the in vitro BBB model using human brain microvascular endothelial cells has facilitated our understanding of the microbial translocation of the BBB, a key step for the acquisition of CNS infections. Recent studies have revealed that microbial translocation of the BBB involves host cell actin cytoskeletal rearrangements, most likely as the result of specific microbial-host interactions. A better understanding of microbial-host interactions that are involved in microbial translocation of the BBB should help in developing new strategies to prevent CNS infections. This review summarises our current understanding of the pathogenic mechanisms involved in translocation of the BBB by meningitis-causing bacteria, fungi and parasites.

Meningitis-Associated Escherichia coli

Escherichia coliis the most common Gram-negative organism causing neonatal meningitis. Neonatal E. colimeningitis continues to be an important cause of mortality and morbidity throughout the world. Our incomplete knowledge of its pathogenesis and pathophysiology contributes to such mortality and morbidity. Recent reports of neonatal meningitis caused by E. coli strains producing CTX-M-type or TEM-type extended-spectrum β-lactamases create a challenge. E. colipenetration into the brain, the essential step in the development of E. coli meningitis, requires a high-degree of bacteremia and penetration of the blood-brain barrier as live bacteria, but the underlying mechanisms remain incompletely understood. Recent functional genomic approaches of meningitis-causing E. coli in both in vitro and in vivo models of the blood-brain barrier (e.g., human brain microvascular endothelial cells and animal models of experimental hematogenousE. colimeningitis, respectively) have identified several E. coli factors contributing to a high-degree of bacteremia, as well as specific microbial factors contributing to E. coli invasion of the blood-brain barrier. In addition, E. coli penetration of the blood-brain barrier involves specific host factors as well as microbe- and host-specific signaling molecules. Blockade of such microbial and host factors and host cell signaling molecules is efficient in preventing E. coli penetration into the brain. Continued investigation of the microbial and host factors contributing to E. colibacteremia andinvasion of the blood-brain barrier is likely to identify new targets for prevention and therapy of E. coli meningitis, thereby limiting the exposure to emerging antimicrobial-resistant E. coli.