Escherichia coli K1 Modulates Peroxisome Proliferator-Activated Receptor γ and Glucose Transporter 1 at the Blood-Brain Barrier in Neonatal Meningitis

Cerebrospinal fluid glucose is not altered in patients with dementia

BACKGROUND

Studies have shown that the pathological changes of many dementia disorders begin several years before clinical onset. A connection between some of these pathophysiological changes and brain hypometabolism, seen in dementia disorders, is well established. Glucose is transported from the blood into the interstitial space, and the decreased demand for glucose by the degenerating brain tissue may thereby mirror increased levels of cerebrospinal fluid (CSF) glucose. In this study, the levels of CSF and plasma glucose and the CSF/plasma glucose ratio were investigated in a large cohort from a mixed memory clinic population in order to evaluate its diagnostic potential.

METHOD

CSF and plasma samples were taken from 446 patients (Alzheimer's Disease (AD) (n = 320), vascular dementia (VaD) (n = 64), frontotemporal dementia (FTD) (n = 27) and dementia with Lewy bodies (DLB) (n = 35)), and 130 healthy controls (HC) (healthy subjects (HS) (n = 34), non-demented HS (n = 96)).

RESULTS

No significant differences were found for CSF and plasma glucose or the CSF/plasma glucose ratio between patients with dementia disorders and HC. In addition, no significant differences were observed between the different dementia etiologies.

CONCLUSION

CSF and plasma glucose were not useful to differentiate between HC and patients with various dementia disorders.

SpyPhage: A Cell-Free TXTL Platform for Rapid Engineering of Targeted Phage Therapies

The past decade has seen the emergence of multidrug resistant pathogens as a leading cause of death worldwide, reigniting interest in the field of phage therapy. Modern advances in the genetic engineering of bacteriophages have enabled several useful results including host range alterations, constitutive lytic growth, and control over phage replication. However, the slow licensing process of genetically modified organisms clearly inhibits the rapid therapeutic application of novel engineered variants necessary to fight mutant pathogens that emerge throughout the course of a pandemic. As a solution to this problem, we propose the SpyPhage system where a "scaffold" bacteriophage is engineered to incorporate a SpyTag moiety on its capsid head to enable rapid postsynthetic modification of their surfaces with SpyCatcher-fused therapeutic proteins. As a proof of concept, through CRISPR/Cas-facilitated phage engineering and whole genome assembly, we targeted a SpyTag capsid fusion to K1F, a phage targeting the pathogenic strain Escherichia coli K1. We demonstrate for the first time the cell-free assembly and decoration of the phage surface with two alternative fusion proteins, SpyCatcher-mCherry-EGF and SpyCatcher-mCherry-Rck, both of which facilitate the endocytotic uptake of the phages by a urinary bladder epithelial cell line. Overall, our work presents a cell-free phage production pipeline for the generation of multiple phenotypically distinct phages with a single underlying "scaffold" genotype. These phages could become the basis of next-generation phage therapies where the knowledge-based engineering of numerous phage variants would be quickly achievable without the use of live bacteria or the need to repeatedly license novel genetic alterations.

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.

ClbG in Avian Pathogenic Escherichia coli Contributes to Meningitis Development in a Mouse Model

Colibactin is a complex secondary metabolite that leads to genotoxicity that interferes with the eukaryotic cell cycle. It plays an important role in many diseases, including neonatal mouse sepsis and meningitis. Avian pathogenic Escherichia coli (APEC) is responsible for several diseases in the poultry industry and may threaten human health due to its potential zoonosis. In this study, we confirmed that clbG was necessary for the APEC XM strain to produce colibactin. The deletion of clbG on APEC XM contributed to lowered γH2AX expression, no megalocytosis, and no cell cycle arrest in vitro. None of the 4-week Institute of Cancer Research mice infected with the APEC XM ΔclbG contracted meningitis or displayed weakened clinical symptoms. Fewer histopathological lesions were observed in the APEC XM ΔclbG group. The bacterial colonization of tissues and the relative expression of cytokines (IL-1β, IL-6, and TNF-α) in the brains decreased significantly in the APEC XM ΔclbG group compared to those in the APEC XM group. The tight junction proteins (claudin-5, occludin, and ZO-1) were not significantly destroyed in APEC XM ΔclbG group in vivo and in vitro. In conclusion, clbG is necessary for the synthesis of the genotoxin colibactin and affects the development of APEC meningitis in mice.

Meningitis

PURPOSE OF REVIEW

This article reviews the diagnosis and treatment of infectious meningitis, including updates on newer molecular diagnostic techniques for microbiological diagnosis.

RECENT FINDINGS

New polymerase chain reaction (PCR)-based molecular diagnostic techniques have improved the timeliness of microbiological diagnosis in meningitis, but clinicians must be aware of the limitations of such tests. Next-generation sequencing can now be applied to CSF, allowing for diagnosis of infections not identifiable by conventional means.

SUMMARY

Infectious meningitis can be caused by a broad range of organisms. The clinician must be aware of the test characteristics of new molecular techniques for microbiological diagnosis as well as traditional techniques to tailor antimicrobial therapy appropriately in patients with meningitis.

Virulence factor-dependent basolateral invasion of choroid plexus epithelial cells by pathogenic Escherichia coli in vitro

Escherichia coli is the most common Gram-negative causative agent of neonatal meningitis and E. coli meningitis is associated with high morbidity and mortality. Previous research has been carried out with regard to the blood-brain barrier and thereby unveiled an assortment of virulence factors involved in E. coli meningitis. Little, however, is known about the role of the blood-cerebrospinal fluid (CSF) barrier (BCSFB), in spite of several studies suggesting that the choroid plexus (CP) is a possible entry point for E. coli into the CSF spaces. Here, we used a human CP papilloma (HIBCPP) cell line that was previously established as valid model for the study of the BCSFB. We show that E. coli invades HIBCPP cells in a polar fashion preferentially from the physiologically relevant basolateral side. Moreover, we demonstrate that deletion of outer membrane protein A, ibeA or neuDB genes results in decreased cell infection, while absence of fimH enhances invasion, although causing reduced adhesion to the apical side of HIBCPP cells. Our findings suggest that the BCSFB might constitute an entry point for E. coli into the central nervous system, and HIBCPP cells are a valuable tool for investigating E. coli entry of the BCSFB.

Engineered K1F bacteriophages kill intracellular Escherichia coli K1 in human epithelial cells

Bacterial infections can be treated with bacteriophages that show great specificity towards their bacterial host and can be genetically modified for different applications. However, whether and how bacteriophages can kill intracellular bacteria in human cells remains elusive. Here, using CRISPR/Cas selection, we have engineered a fluorescent bacteriophage specific for E. coli K1, a nosocomial pathogen responsible for urinary tract infections, neonatal meningitis and sepsis. By confocal and live microscopy, we show that engineered bacteriophages K1F-GFP and E. coli EV36-RFP bacteria displaying the K1 capsule, enter human cells via phagocytosis. Importantly, we show that bacteriophage K1F-GFP efficiently kills intracellular E. coli EV36-RFP in T24 human urinary bladder epithelial cells. Finally, we provide evidence that bacteria and bacteriophages are degraded by LC3-associated phagocytosis and xenophagy.

Thiazolidinediones and reduced risk of incident bacterial abscess in adults with type 2 diabetes: A population-based cohort study

AIM

Previous research has suggested that peroxisome proliferator-activated receptor-gamma (PPAR-γ) may play an important role in immunomodulation. We aimed to examine the association between thiazolidinediones, PPAR-γ agonists and incidence of bacterial abscess among patients with type 2 diabetes.

MATERIALS AND METHODS

This retrospective cohort study between 2000 and 2010 included 46 986 propensity (PS)-matched patients diagnosed with type 2 diabetes. We compared the incidence of bacterial abscess, including liver and non-liver abscesses, between patients treated with metformin plus a thiazolidinedione (M + T, N = 7831) or metformin plus a sulfonylurea (M + S, N = 39 155). Data were retrieved from a population-based Taiwanese database. We applied Cox proportional hazard regression models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), comparing M + T and M + S after PS matching.

RESULTS

During a median follow-up of 4.5 years, the incidence rate of bacterial abscess was lower with M + T than with M + S treatment (1.89 vs 3.15 per 1000 person-years) in the PS-matched cohort. M + T was associated with a reduced risk of bacterial abscess (HRs after PS matching, 0.58; 95% CI, 0.42-0.80 for total bacterial abscess; 0.54; 95% CI, 0.28-1.07 for liver abscess; 0.59; 95% CI, 0.41-0.85 for non-liver abscess). Results did not change materially after accounting for unmeasured confounding factors using high-dimenional PS matching and differential censoring between regimen groups. Rosiglitazone and pioglitazone, in combination with metformin, produced similar reductions in risk of all abscess outcomes.

CONCLUSION

We found that M + T may provide a protective benefit in reducing the incidence of bacterial abscesses. These findings merit further investigation.

Biology of Microglia in the Developing Brain

Microglia exist in different morphological forms in the developing brain. They show a small cell body with scanty cytoplasm with many branching processes in the grey matter of the developing brain. However, in the white matter such as the corpus callosum where the unmyelinated axons are loosely organized, they appear in an amoeboid form having a round cell body endowed with copious cytoplasm rich in organelles. The amoeboid cells eventually transform into ramified microglia in the second postnatal week when the tissue becomes more compact with the onset of myelination. Microglia serve as immunocompetent macrophages that act as neuropathology sensors to detect and respond swiftly to subtle changes in the brain tissues in pathological conditions. Microglial functions are broadly considered as protective in the normal brain development as they phagocytose dead cells and sculpt neuronal connections by pruning excess axons and synapses. They also secrete a number of trophic factors such as insulin-like growth factor-1 and transforming growth factor-β among many others that are involved in neuronal and oligodendrocyte survival. On the other hand, microglial cells when activated produce a plethora of molecules such as proinflammatory cytokines, chemokines, reactive oxygen species, and nitric oxide that are implicated in the pathogenesis of many pathological conditions such as epilepsy, cerebral palsy, autism, and perinatal hypoxic-ischemic brain injury. Although many studies have investigated the origin and functions of the microglia in the developing brain, in-depth in vivo studies along with analysis of their transcriptome and epigenetic changes need to be undertaken to elucidate their full potential be it protective or neurotoxic. This would lead to a better understanding of their roles in the healthy and diseased developing brain and advancement of therapeutic strategies to target microglia-mediated neurotoxicity.