Listeria monocytogenes crosses blood brain barrier through Rho GTPases induced migration of macrophages and inflammatory interleukin expression

Potential mechanisms of Treponema pallidum breaching the blood-brain barrier

Syphilis, a sexually transmitted disease caused by Treponema pallidum subsp. pallidum (T. pallidum), can lead to a complication known as neurosyphilis. Neurosyphilis affects multiple components of the nervous system, including the meninges, blood vessels, brain parenchyma, and others, significantly impacting the central nervous system (CNS). Despite the effective control of syphilis spread by antibiotics, recent years have seen a resurgence in incidence among high-risk populations. The blood-brain barrier (BBB) is a critical defense for the CNS, preventing toxins and pathogens, including viruses, from entering and ensuring CNS function. The exact mechanisms of how T. pallidum penetrates the BBB are still not fully understood. Extensive research suggests that T. pallidum can disrupt endothelial cells and intercellular junctions, as well as induce abnormal activation of immune cells and aberrant cytokine expression, potentially facilitating its breach of BBB. Based on current research, we focus on the detrimental effects of cytokines on BBB integrity. We have also summarized the pathways T. pallidum uses to penetrate cellular barriers. Understanding the interaction between T. pallidum and the BBB is essential for revealing neurosyphilis pathogenesis and developing new therapies. DATA AVAILABILITY: Data used to support the findings of this study are included in the article.

From cytokines to chemokines: Understanding inflammatory signaling in bacterial meningitis

Bacterial meningitis is a serious central nervous system (CNS) infection, claiming millions of human lives annually around the globe. The deadly infection involves severe inflammation of the protective sheath of the brain, i.e., meninges, and sometimes also consists of the brain tissue, called meningoencephalitis. Several inflammatory pathways involved in the pathogenesis of meningitis caused by Streptococcus pneumoniae, Neisseria meningitidis, Escherichia coli, Haemophilus influenzae, Mycobacterium tuberculosis, Streptococcus suis, etc. are mentioned in the scientific literature. Many in-vitro and in-vivo analyses have shown that after the disruption of the blood-brain barrier (BBB), these pathogens trigger several inflammatory pathways including Toll-Like Receptor (TLR) signaling in response to Pathogen-Associated Molecular Patterns (PAMPs), Nucleotide oligomerization domain (NOD)-like receptor-mediated signaling, pneumolysin related signaling, NF-κB signaling and many other pathways that lead to pro-inflammatory cascade and subsequent cytokine release including interleukine (IL)-1β, tumor necrosis factor(TNF)-α, IL-6, IL-8, chemokine (C-X-C motif) ligand 1 (CXCL1) along with other mediators, leading to neuroinflammation. The activation of another protein complex, nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome, also takes place resulting in the maturation and release of IL-1β and IL-18, hence potentiating neuroinflammation. This review aims to outline the inflammatory signaling pathways associated with the pathogenesis of bacterial meningitis leading to extensive pathological changes in neurons, astrocytes, oligodendrocytes, and other central nervous system cells.

Modification of Silver Nanoplates with Cell-Binding Subunit of Bacterial Toxin and Their Antimicrobial Activity against Intracellular Bacteria

Intracellular bacteria are able to survive and grow in host cells and often cause serious infectious diseases. The B subunit of the subtilase cytotoxin (SubB) found in enterohemorrhagic Escherichia coli O113:H21 recognizes sialoglycans on cell surfaces and triggers the uptake of cytotoxin by the cells, meaning that Sub B is a ligand molecule that is expected to be useful for drug delivery into cells. In this study, we conjugated SubB to silver nanoplates (AgNPLs) for use as an antibacterial drug and examined their antimicrobial activity against intracellularly infecting Salmonella typhimurium (S. typhimurium). The modification of AgNPLs with SubB improved their dispersion stability and antibacterial activity against planktonic S. typhimurium. The SubB modification enhanced the cellular uptake of AgNPLs, and intracellularly infecting S. typhimurium were killed at low concentrations of AgNPLs. Interestingly, larger amounts of SubB-modified AgNPLs were taken up by infected cells compared with uninfected cells. These results suggest that the S. typhimurium infection activated the uptake of the nanoparticles into the cells. SubB-modified AgNPLs are expected to be useful bactericidal systems for intracellularly infecting bacteria.

Clinical Characteristics and Treatment of Listeria monocytogenes Infections in the Central Nervous System

Purpose

Listeria monocytogenes infections are rare in the central nervous system (CNS) and frequently difficult-to-diagnose. Our goal is to assess CNS listeriosis patients' clinical characteristics, diagnosis, treatment, and prognosis.

Patients and Methods

Patients with CNS listeriosis admitted to the Department of neurology, the first medical center of the Chinese PLA general hospital, were enrolled in this study from March 2018 to August 2022.

Results

This study analyzed eight adults, including five males and three females. The average age of onset was (50.25 ± 11.52) years. The clinical manifestations included fever, headache, altered mental status, vomiting, seizures, neck rigidity, hemiplegia and cranial nerve palsies. Cerebrospinal fluid (CSF) tests revealed intracranial hypertension, elevated cell count and protein concentration, and decreased glucose levels. The positive rates of blood and CSF culture were 40% and 28.57%, respectively. All patients underwent CSF metagenomic next-generation sequencing (mNGS), with a 100% positive rate and the specific read number 12-20394. Magnetic resonance imaging (MRI) exhibited leptomeningitis, meningoencephalitis, and brain abscess, and no specific changes were discovered in two patients. All patients received antibiotic treatment, seven were cured, and one died.

Conclusion

Monitoring the proportion of monocytes in blood and mNGS results of CSF can play a crucial role in diagnosing pathogens. Early and sufficient application of two to three sensitive antibiotics with a BBB permeability of 20-30% for at least 2-3 months can significantly improve CNS listeriosis prognosis.

Blood-Brain Barrier Integrity Damage in Bacterial Meningitis: The Underlying Link, Mechanisms, and Therapeutic Targets

Despite advances in supportive care and antimicrobial treatment, bacterial meningitis remains the most serious infection of the central nervous system (CNS) that poses a serious risk to life. This clinical dilemma is largely due to our insufficient knowledge of the pathology behind this disease. By controlling the entry of molecules into the CNS microenvironment, the blood-brain barrier (BBB), a highly selective cellular monolayer that is specific to the CNS's microvasculature, regulates communication between the CNS and the rest of the body. A defining feature of the pathogenesis of bacterial meningitis is the increase in BBB permeability. So far, several contributing factors for BBB disruption have been reported, including direct cellular damage brought on by bacterial virulence factors, as well as host-specific proteins or inflammatory pathways being activated. Recent studies have demonstrated that targeting pathological factors contributing to enhanced BBB permeability is an effective therapeutic complement to antimicrobial therapy for treating bacterial meningitis. Hence, understanding how these meningitis-causing pathogens affect the BBB permeability will provide novel perspectives for investigating bacterial meningitis's pathogenesis, prevention, and therapies. Here, we summarized the recent research progress on meningitis-causing pathogens disrupting the barrier function of BBB. This review provides handy information on BBB disruption by meningitis-causing pathogens, and helps design future research as well as develop potential combination therapies.

Targeted Drug Delivery Systems for Eliminating Intracellular Bacteria

The intracellular survival of pathogenic bacteria requires a range of survival strategies and virulence factors. These infections are a significant clinical challenge, wherein treatment frequently fails because of poor antibiotic penetration, stability, and retention in host cells. Drug delivery systems (DDSs) are promising tools to overcome these shortcomings and enhance the efficacy of antibiotic therapy. In this review, the classification and the mechanisms of intracellular bacterial persistence are elaborated. Furthermore, the systematic design strategies applied to DDSs to eliminate intracellular bacteria are also described, and the strategies used for internalization, intracellular activation, bacterial targeting, and immune enhancement are highlighted. Finally, this overview provides guidance for constructing functionalized DDSs to effectively eliminate intracellular bacteria.

A Retrospective Study of Rare Listeria Meningoencephalitis in Immunocompetent Children in China

Objectives

Listeria meningoencephalitis (LMM) is very rare in healthy children. We aimed to assess the clinical features, differential diagnosis, treatment options, and outcomes of LMM in immunocompetent children through a retrospective study.

Methods

The clinical symptoms, laboratory findings, imaging features, antibiotic use, and metagenomic next-generation sequencing (mNGS) results of the cerebrospinal fluid (CSF) were obtained from immunocompetent children who were diagnosed with LMM and admitted to the Xi'an Children's Hospital from May 2018 to July 2020.

Results

The data from 8 immunocompetent children were retrospectively analyzed in this study. The cohort included data from 5 males and 3 females who were aged from 1 year and 7 months to 16 years and 6 months. A total of 4 patients had chilled food before onset. The complications included hyponatremia (3/8), hydrocephalus (2/8), and hemophagocytic syndrome (1/8). In total, 8 patients were diagnosed with Listeria monocytogenes by positive CSF culture or mNGS results. The positive rate of CSF culture was 62.5% (5/8). A total of 5 patients conducted CSF mNGS, and the results of the mNGS were positive in 4 patients (80%, 4/5) and suspected in 1 patient. A total of 7 patients changed their therapeutic regimen to combined antibacterial therapies that included linezolid and meropenem (5/8), or ampicillin and meropenem (2/8). A total of 5 patients had favorable outcomes (Glasgow Outcome Scale, GOSE = 5) while two patients had unfavorable outcomes (GOSE = 1) and were complicated with hyponatremia and hydrocephalus.

Conclusions

Listeria meningoencephalitis (LMM) can occur in children with normal immune function and is commonly mistaken for other central nervous system infections. L. monocytogenes can be quickly and accurately detected by mNGS. Hyponatremia and hydrocephalus may indicate unfavorable outcomes.