Targeting of the central nervous system by Listeria monocytogenes

RECON gene disruption enhances host resistance to enable genome-wide evaluation of intracellular pathogen fitness during infection

Transposon sequencing (Tn-seq) is a powerful genome-wide technique to assess bacterial fitness under varying growth conditions. However, screening via Tn-seq in vivo is challenging. Dose limitations and host restrictions create bottlenecks that diminish the transposon mutant pool being screened. Here, we have developed a murine model with a disruption in Akr1c13 that renders the resulting RECON-/- mouse resistant to high-dose infection. We leveraged this model to perform a Tn-seq screen of the human pathogen Listeria monocytogenes in vivo. We identified 135 genes which were required for L. monocytogenes growth in mice including novel genes not previously identified for host survival. We identified organ-specific requirements for L. monocytogenes survival and investigated the role of the folate enzyme FolD in L. monocytogenes liver pathogenesis. A mutant lacking folD was impaired for growth in murine livers by 2.5-log10 compared to wild type and failed to spread cell-to-cell in fibroblasts. In contrast, a mutant in alsR, which encodes a transcription factor that represses an operon involved in D-allose catabolism, was attenuated in both livers and spleens of mice by 4-log10 and 3-log10, respectively, but showed modest phenotypes in in vitro models. We confirmed that dysregulation of the D-allose catabolism operon is responsible for the in vivo growth defect, as deletion of the operon in the ∆alsR background rescued virulence. By undertaking an unbiased, genome-wide screen in mice, we have identified novel fitness determinants for L. monocytogenes host infection, which highlights the utility of the RECON-/- mouse model for future screening efforts.

IMPORTANCE

Listeria monocytogenes is the gram-positive bacterium responsible for the food-borne disease listeriosis. Although infections with L. monocytogenes are limiting in healthy hosts, vulnerable populations, including pregnant and elderly people, can experience high rates of mortality. Thus, understanding the breadth of genetic requirements for L. monocytogenes in vivo survival will present new opportunities for treatment and prevention of listeriosis. We developed a murine model of infection using a RECON-/- mouse that is restrictive to systemic L. monocytogenes infection. We utilized this model to screen for L. monocytogenes genes required in vivo via transposon sequencing. We identified the liver-specific gene folD and a repressor, alsR, that only exhibits an in vivo growth defect. AlsR controls the expression of the D-allose operon which is a marker in diagnostic techniques to identify pathogenic Listeria. A better understanding of the role of the D-allose operon in human disease may further inform diagnostic and prevention measures.

Imaging modalities in neurolisteriosis: a literature review

Listeriosis caused by Listeria monocytogenes due to its ability to withstand harsh conditions and form biofilms on post-processed food poses a serious public health issue. It typically manifests itself with fever and gastrointestinal symptoms, but it can escalate with life-threatening conditions, especially in immunocompromised patients, the elderly, oncologically sick, and even pregnant women. The diagnosis is based on blood and cerebrospinal fluid culture growth, but it presents significant challenges due to deceptive findings and low positivity rates, the golden standard includes molecular diagnostic tests such as real-time PCR and metagenomic next-generation sequencing, which offer higher sensitivity and rapid detection. Radiological imaging, particularly magnetic resonance imaging, can play a crucial role in diagnosis of central nervous system (CNS) invasion by L. monocytogenes, enabling the detection of characteristic CNS lesions. The aim of the paper was to sum up the imaging features of L. monocytogenes CNS invasions in conventional imaging techniques, which can potentially speed up the diagnostic workflow for patients presenting with neurological symptoms associated with L. monocytogenes infection, particularly when conventional tests yield inconclusive results.

Biofilm Formation, Motility, and Virulence of Listeria monocytogenes Are Reduced by Deletion of the Gene lmo0159, a Novel Listerial LPXTG Surface Protein

Listeria monocytogenes (L. monocytogenes) is a foodborne pathogen that causes listeriosis in humans and other animals. Surface proteins with the LPXTG motif have important roles in the virulence of L. monocytogenes. Lmo0159 is one such protein, but little is known about its role in L. monocytogenes virulence, motility, and biofilm formation. Here, we constructed and characterized a deletion mutant of lmo0159 (∆lmo0159). We analyzed not only the capacity of biofilm formation, motility, attachment, and intracellular growth in different cell types but also LD50; bacterial load in mice's liver, spleen, and brain; expression of virulence genes; and survival time of mice after challenge. The results showed that the cross-linking density of the biofilm of ∆lmo0159 strain was lower than that of WT by microscopic examination. The expression of biofilm-formation and virulence genes also decreased in the biofilm state. Subsequently, the growth and motility of ∆lmo0159 in the culture medium were enhanced. Conversely, the growth and motility of L. monocytogenes were attenuated by ∆lmo0159 at both the cellular and mouse levels. At the cellular level, ∆lmo0159 reduced plaque size; accelerated scratch healing; and attenuated the efficiency of adhesion, invasion, and intracellular proliferation in swine intestinal epithelial cells (SIEC), RAW264.7, mouse-brain microvascular endothelial cells (mBMEC), and human-brain microvascular endothelial cells (hCMEC/D3). The expression of virulence genes was also inhibited. At the mouse level, the LD50 of the ∆lmo0159 strain was 100.97 times higher than that of the WT strain. The bacterial load of the ∆lmo0159 strain in the liver and spleen was lower than that of the WT strain. In a mouse model of intraperitoneal infection, the deletion of the lmo0159 gene significantly prolonged the survival time of the mice, suggesting that the lmo0159 deletion mutant also exhibited reduced virulence. Thus, our study identified lmo0159 as a novel virulence factor among L. monocytogenes LPXTG proteins.

Unveiling the intratumoral microbiota within cancer landscapes

Recent advances in cancer research have unveiled a significant yet previously underappreciated aspect of oncology: the presence and role of intratumoral microbiota. These microbial residents, encompassing bacteria, fungi, and viruses within tumor tissues, have been found to exert considerable influence on tumor development, progression, and the efficacy of therapeutic interventions. This review aims to synthesize these groundbreaking discoveries, providing an integrated overview of the identification, characterization, and functional roles of intratumoral microbiota in cancer biology. We focus on elucidating the complex interactions between these microorganisms and the tumor microenvironment, highlighting their potential as novel biomarkers and therapeutic targets. The purpose of this review is to offer a comprehensive understanding of the microbial dimension in cancer, paving the way for innovative approaches in cancer diagnosis and treatment.

Computed tomography and magnetic resonance imaging findings in central nervous system listeriosis

PURPOSE

To describe the imaging findings and determine the incidence of a characteristic worm-like pattern along the white matter tracts in neurolisteriosis on CT/MRI.

METHODS

An IRB-approved retrospective study in 21 consecutive neurolisteriosis cases during January 2002-July 2020. At least one of the following is required: (1) Positive Listeria monocytogenes (LM) in blood with clinical signs of meningeal irritation and/or abnormal CSF profile, (2) positive LM in blood with signs of encephalitis, (3) positive LM in CSF, (4) positive LM from brain biopsy/aspiration. Six cases were excluded due to the lack of contrast-enhanced images, leaving a total of 15 cases for analysis (mean age 53.5 years ± 18.8 SD). The imaging studies were independently reviewed by two blinded readers. Demographic data, imaging findings, and incidence of the worm-like pattern were reported. The Cohen's kappa was used to calculate interrater reproducibility.

RESULTS

Of the 12 patients with relevant imaging findings, nine cases (75%) had parenchymal lesions (eight cases in supratentorial compartment and one case in infratentorial compartment), four cases (33.3%) had leptomeningeal enhancement and two cases (16.7%) had hydrocephalus. Brain abscesses were found in eight cases and nodules evocative of abscess in one case. Restricted diffusion in the central area and hemosiderin deposition were observed in all cases. The involvement of white matter tract in a worm-like pattern was demonstrated in eight of nine patients with parenchymal lesions (88.9%).

CONCLUSION

Abnormal findings in brain CT/MRI images are common in neurolisteriosis. The incidence of worm-like spread along the white matter tracts is high and may help diagnose suspicious patients.

Brain Abscess Caused by Listeria monocytogenes: A Rare Case of Supratentorial Neurolisteriosis

Listeria monocytogenes is a Gram-positive bacillus that presents a tropism for the central nervous system (CNS). In fact, CNS involvement occurs in over two-thirds of infections caused by this agent. Meningitis is the most common manifestation, while brain abscess is rare. We present the case of a 77-year-old male patient on corticosteroid treatment for bronchiolitis obliterans organizing pneumonia with a history of unpasteurized cheese consumption, who presented with fever and altered mental status. Brain computerized tomography scan revealed left frontal cortico-subcortical hypodensity mimicking an ischemic stroke. Subsequent magnetic resonance imaging revealed a brain abscess, and blood cultures yielded Listeria monocytogenes. A good clinical outcome was achieved after appropriate antimicrobial therapy and abscess drainage. This case underscores the importance of considering Listeria monocytogenes in CNS infections, especially in immunocompromised individuals over 65 years of age. The atypical supratentorial involvement challenges the more common rhombencephalitis presentation. Maintaining a high level of suspicion in relevant populations is crucial for timely diagnosis and intervention, especially in patients with comorbidities, who present particularly high mortality rates.

A Comprehensive Review of the Common Bacterial Infections in Dairy Calves and Advanced Strategies for Health Management

Dairy farming faces a significant challenge of bacterial infections in dairy calves, which can have detrimental effects on their health and productivity. This review offers a comprehensive overview of the most prevalent bacterial infections in dairy calves, including Escherichia coli, Salmonella typhimurium, Salmonella dublin, Salmonella enterica, Clostridium perfringens, Pasteurella multocida, Listeria monocytogenes, Mycoplasma bovis, and Haemophilus somnus. These pathogens can cause various clinical signs and symptoms, leading to diarrhea, respiratory distress, septicemia, and even mortality. Factors such as management practices, environmental conditions, and herd health influence the incidence and severity of the infections. Efficient management and prevention strategies include good colostrum and nutrient feeding, early detection, appropriate treatment, hygiene practices, and supportive care. Regular health monitoring and diagnostic tests facilitate early detection and intervention. The use of antibiotics should be judicious to prevent antimicrobial resistance and supportive care such as fluid therapy and nutritional support promotes recovery. Diagnostic methods, including immunological tests, culture, polymerase chain reaction (PCR), and serology, aid in the identification of specific pathogens. This review also explores recent advancements in the diagnosis, treatment, and prevention of bacterial infections in dairy calves, providing valuable insights for dairy farmers, veterinarians, and researchers. By synthesizing pertinent scientific literature, this review contributes to the development of effective strategies aimed at mitigating the impact of bacterial infections on the health, welfare, and productivity of young calves. Moreover, more research is required to enhance the understanding of the epidemiology and characterization of bacterial infections in dairy calves.

Clinical Findings of Listeria monocytogenes Infections with a Special Focus on Bone Localizations

Listeria monocytogenes is a Gram-positive pathogenic bacterium which can be found in soil or water. Infection with the microorganism can occur after ingestion of contaminated food products. Small and large outbreaks of listeriosis have been described in the past. L. monocytogenes can cause a number of different clinical syndromes, most frequently sepsis, meningitis, and rhombencephalitis, particularly in immunocompromised hosts. L. monocytogenes systemic infections can develop following tissue penetration across the gastrointestinal tract or to hematogenous spread to sterile sites, possibly evolving towards bacteremia. L. monocytogenes only rarely causes bone or joint infections, usually in the context of prosthetic material that can provide a site for bacterial seeding. We describe here the clinical findings of invasive listeriosis, mainly focusing on the diagnosis, clinical management, and treatment of bone and vertebral infections occurring in the context of invasive listeriosis.

Concurrent Infection of the Human Brain with Multiple Borrelia Species

Lyme disease (LD) spirochetes are well known to be able to disseminate into the tissues of infected hosts, including humans. The diverse strategies used by spirochetes to avoid the host immune system and persist in the host include active immune suppression, induction of immune tolerance, phase and antigenic variation, intracellular seclusion, changing of morphological and physiological state in varying environments, formation of biofilms and persistent forms, and, importantly, incursion into immune-privileged sites such as the brain. Invasion of immune-privileged sites allows the spirochetes to not only escape from the host immune system but can also reduce the efficacy of antibiotic therapy. Here we present a case of the detection of spirochetal DNA in multiple loci in a LD patient's post-mortem brain. The presence of co-infection with Borrelia burgdorferi sensu stricto and Borrelia garinii in this LD patient's brain was confirmed by PCR. Even though both spirochete species were simultaneously present in human brain tissue, the brain regions where the two species were detected were different and non-overlapping. The presence of atypical spirochete morphology was noted by immunohistochemistry of the brain samples. Atypical morphology was also found in the tissues of experimentally infected mice, which were used as a control.

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.

Citrus By-Products as a Valuable Source of Biologically Active Compounds with Promising Pharmaceutical, Biological and Biomedical Potential

Citrus fruits processing results in the generation of huge amounts of citrus by-products, mainly peels, pulp, membranes, and seeds. Although they represent a major concern from both economical and environmental aspects, it is very important to emphasize that these by-products contain a rich source of value-added bioactive compounds with a wide spectrum of applications in the food, cosmetic, and pharmaceutical industries. The primary aim of this review is to highlight the great potential of isolated phytochemicals and extracts of individual citrus by-products with bioactive properties (e.g., antitumor, antimicrobial, antiviral, antidiabetic, antioxidant, and other beneficial activities with health-promoting abilities) and their potential in pharmaceutical, biomedical, and biological applications. This review on citrus by-products contains the following parts: structural and chemical characteristics; the utilization of citrus by-products; bioactivities of the present waxes and carotenoids, essential oils, pectins, and phenolic compounds; and citrus by-product formulations with enhanced biocactivities. A summary of the recent developments in applying citrus by-products for the treatment of different diseases and the protection of human health is also provided, emphasizing innovative methods for bioaccessibility enhancements (e.g., extract/component encapsulation, synthesis of biomass-derived nanoparticles, nanocarriers, or biofilm preparation). Based on the representative phytochemical groups, an evaluation of the recent studies of the past six years (from 2018 to 2023) reporting specific biological and health-promoting activities of citrus-based by-products is also provided. Finally, this review discusses advanced and modern approaches in pharmaceutical/biological formulations and drug delivery (e.g., carbon precursors for the preparation of nanoparticles with promising antimicrobial activity, the production of fluorescent nanoparticles with potential application as antitumor agents, and in cellular imaging). The recent studies implementing nanotechnology in food science and biotechnology could bring about new insights into providing innovative solutions for new pharmaceutical and medical discoveries.

Intestinal infection triggers mitochondria-mediated α-synuclein pathology: relevance to Parkinson's disease

Parkinson's disease (PD) is a multifactorial neurodegenerative disease characterized by the loss of dopaminergic neurons in the midbrain. In the prodromal phase several autonomic symptoms including orthostatic hypotension and constipation are correlated with increased α-synuclein pathology in peripheral tissues. It is currently accepted that some idiopathic PD cases may start in the gut (body-first PD) with accumulation of pathological α-synuclein in enteric neurons that may subsequently propagate caudo-rostrally to the central nervous system. In addition to the already-established regulation of synaptic vesicle trafficking, α-synuclein also seems to play a role in neuronal innate immunity after infection. Our goal was to understand if seeding the gut with the foodborne pathogen Listeria monocytogenes by oral gavage would impact gut immunity and eventually the central nervous system. Our results demonstrate that L. monocytogenes infection induced oligomerization of α-synuclein in the ileum, along with a pronounced pro-inflammatory local and systemic response that ultimately culminated in neuronal mitochondria dysfunction. We propose that, having evolved from ancestral endosymbiotic bacteria, mitochondria may be directly targeted by virulence factors of intracellular pathogens, and that mitochondrial dysfunction and fragmentation resulting also from the activation of the innate immune system at the gut level, trigger innate immune responses in midbrain neurons, which include α-synuclein oligomerization and neuroinflammation, all of which hallmarks of PD.

Human Listeriosis

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that can cause severe invasive infections upon ingestion with contaminated food. Clinically, listerial disease, or listeriosis, most often presents as bacteremia, meningitis or meningoencephalitis, and pregnancy-associated infections manifesting as miscarriage or neonatal sepsis. Invasive listeriosis is life-threatening and a main cause of foodborne illness leading to hospital admissions in Western countries. Sources of contamination can be identified through international surveillance systems for foodborne bacteria and strains' genetic data sharing. Large-scale whole genome studies have increased our knowledge on the diversity and evolution of L. monocytogenes, while recent pathophysiological investigations have improved our mechanistic understanding of listeriosis. In this article, we present an overview of human listeriosis with particular focus on relevant features of the causative bacterium, epidemiology, risk groups, pathogenesis, clinical manifestations, and treatment and prevention.

Analysis of Clinical and Microbiological Features of Listeria monocytogenes Infection

Introduction

To analyze the demographics and clinical features of 59 cases of Listeria monocytogenes, and determine the predisposing conditions for severe meningitis infections for reference.

Materials and methods

A total of 59 cases isolated L. monocytogenes from 2009 to 2020 were enrolled. Electronic medical record data were used to determine the epidemiological and clinical characteristics of L. monocytogenes infection. Univariate and multifactorial logistic regression analyses were performed to predict risk factors for Listeria meningitis.

Results

A total of 59 cases (median age of 52 years, 30 females and 29 males) were enrolled. Twenty-five patients (42.37%) developed a neuroinvasive infection. The indexes of interleukin-6 (IL-6), CD3+T, CD4+T, and CD8+T cells in the study group were higher than those in the control group (P<0.05). In univariate analysis, the use of hormone drugs (odds ratio=3.21, P=0.000) and immunosuppressive agents (odds ratio=3.06, P=0.000) were relevant predictors of severe meningitis. 47 patients (79.66%) were treated with ampicillin (27.12%), carbapenems (18.64%), quinolones (11.86%), and β-lactamase inhibitors (11.86%) as the primary agents of antimicrobial therapy. Thirty-four patients (57.63%) showed clinical improvement, five patients (8.47%) had a poor prognosis, and two patients (3.39%) died.

Conclusion

Infection with Listeria changed the levels of IL-6, CD3+T, CD4+T, and CD8+T cells, and these analyzing items were significantly different between L. monocytogenes and other bacterial infections. Long-term use of immunosuppressants and hormones may be risk factors for severe adult forms of Listeria-related infections. Sensitive antibiotics, such as penicillins and carbapenems, should be added or replaced in the early empiric treatment of L. monocytogenes.

Progressive cognitive impairment after recovery from neuroinvasive and non-neuroinvasive Listeria monocytogenes infection

Background

Neuro-cognitive impairment is a deleterious complication of bacterial infections that is difficult to treat or prevent. Listeria monocytogenes (Lm) is a neuroinvasive bacterial pathogen and commonly used model organism for studying immune responses to infection. Antibiotic-treated mice that survive systemic Lm infection have increased numbers of CD8⁺ and CD4⁺ T-lymphocytes in the brain that include tissue resident memory (T_RM) T cells, but post-infectious cognitive decline has not been demonstrated. We hypothesized that Lm infection would trigger cognitive decline in accord with increased numbers of recruited leukocytes.

Methods

Male C57BL/6J mice (age 8 wks) were injected with neuroinvasive Lm 10403s, non-neuroinvasive Δhly mutants, or sterile saline. All mice received antibiotics 2-16d post-injection (p.i.) and underwent cognitive testing 1 month (mo) or 4 mo p.i. using the Noldus PhenoTyper with Cognition Wall, a food reward-based discrimination procedure using automated home cage based observation and monitoring. After cognitive testing, brain leukocytes were quantified by flow cytometry.

Results

Changes suggesting cognitive decline were observed 1 mo p.i. in both groups of infected mice compared with uninfected controls, but were more widespread and significantly worse 4 mo p.i. and most notably after Lm 10403s. Impairments were observed in learning, extinction of prior learning and distance moved. Infection with Lm 10403s, but not Δhly Lm, significantly increased numbers of CD8⁺ and CD4⁺ T-lymphocytes, including populations expressing CD69 and T_RM cells, 1 mo p.i. Numbers of CD8⁺, CD69⁺CD8⁺ T-lymphocytes and CD8⁺ T_RM remained elevated at 4 mo p.i. but numbers of CD4⁺ cells returned to homeostatic levels. Higher numbers of brain CD8⁺ T-lymphocytes showed the strongest correlations with reduced cognitive performance.

Conclusions

Systemic infection by neuroinvasive as well as non-neuroinvasive Lm triggers a progressive decline in cognitive impairment. Notably, the deficits are more profound after neuroinvasive infection that triggers long-term retention of CD8⁺ T-lymphocytes in the brain, than after non-neuroinvasive infection, which does not lead to retained cells in the brain. These results support the conclusion that systemic infections, particularly those that lead to brain leukocytosis trigger a progressive decline in cognitive function and implicate CD8⁺ T-lymphocytes, including CD8⁺T_RM in the etiology of this impairment.

Next-generation sequencing for the diagnosis of Listeria monocytogenes meningoencephalitis: a case series of five consecutive patients

Introduction. The prompt and specific diagnosis of Listeria monocytogenes meningoencephalitis (LMM) is challenging. Next-generation sequencing (NGS) of cerebrospinal fluid (CSF) is an emerging technique for diagnosing infrequent causative pathogens.Hypothesis/Gap statement. We hypothesized that NGS of CSF is an effective approach for diagnosing LMM.Aim. To evaluate the effectiveness of NGS, we present five cases of LMM diagnosed using NGS of the CSF.Methodology. Between August 2017 and 30 September 2020, we used NGS of the CSF to detect pathogens in patients with clinically suspected central nervous system infections. The clinical characteristics, laboratory tests, imaging findings and NGS results are reviewed.Results. Five patients were diagnosed with LMM using NGS of the CSF within 2 to 4 days, although the clinical manifestations, medical history and imaging findings varied strikingly. NGS of CSF showed sequence reads corresponding to L. monocytogenes species ranging from 118 to 1997 bp, genomic coverage of 0.29-5.96 %, relative abundance of 14.83-32.16 % and sequencing depth of 1.12 to 1.35. The prompt diagnosis resulted in targeted and effective treatment with the appropriate antibiotics, although two patients with the most severe cerebral parenchymal lesions showed little improvement.Conclusion. Our results demonstrate the power of NGS of CSF for the prompt diagnosis of LMM. NGS of CSF is an important complementary tool for identifying L. monocytogenes.

Novel neurolisteriosis therapy using SPION as a drivable nanocarrier in gallic acid delivery to CNS

Neurolisteriosis is an infectious disease of the central nervous system (CNS) with a high mortality rate caused by Listeria monocytogenes. The CNS disorders suffer from inadequacy of drugs accessibility. An experimental in vivo model of neurolisteriosis was developed by oral administration of the bacteria in Wistar rats. It's speculated the capability of magnetite nanoparticles (MNPs) in ferrying gallic acid (GA), as a natural antimicrobial agent, through the blood-brain barrier (BBB) with the assistance of an external magnetic field (EMF). The capability of the formulated nanodrug in traversing through the BBB was approved by detecting blue spots in the Perls' Prussian staining of the brain tissue sections and by an increased iron content of the brain determined by the inductively coupled plasma spectroscopy. The GA release pattern and the nanodrug toxicity assay were promising. Anti-listeriosis effect of the formulated nanodrug was evaluated by molecular quantification of the relative abundance of survived bacteria in brain tissue samples. Besides, the relative expression of the listeriolysin O-encoding hly gene, the prominent virulence factor of L. monocytogenes, was determined using the rplD gene as a reference gene. The nanodrug-received rats showed a significantly less viable bacteria (13.2 ± 7.6%) and a 4.4-fold reduction in the relative expression of the hly gene in comparison to the sham group. Magnetite nanoparticles (MNPs) were synthesized by co-precipitation method, functionalized with GA, and finally coated with Tween 80. The physicochemical properties of the bare and surface modified materials were investigated using different techniques including X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopies, transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), dynamic light scattering (DLS) and Zeta Potential analyses, and vibrating sample magnetometry. In conclusion, MNPs displayed a considerable potential for drug delivery intentions to various target sites such as the CNS. Gallic acid exhibited a binary anti-listerial effect, the destruction of L. monocytogenes bacteria in addition to reducing the expression of the hly gene, which in turn causes reduced survivability of the bacteria in the CNS.

Bacterial ribosomal RNA detection in cerebrospinal fluid using a viromics approach

BACKGROUND

In patients with central nervous system (CNS) infections identification of the causative pathogen is important for treatment. Metagenomic next-generation sequencing techniques are increasingly being applied to identify causes of CNS infections, as they can detect any pathogen nucleic acid sequences present. Viromic techniques that enrich samples for virus particles prior to sequencing may simultaneously enrich ribosomes from bacterial pathogens, which are similar in size to small viruses.

METHODS

We studied the performance of a viromic library preparation technique (VIDISCA) combined with low-depth IonTorrent sequencing (median ~ 25,000 reads per sample) for detection of ribosomal RNA from common pathogens, analyzing 89 cerebrospinal fluid samples from patients with culture proven bacterial meningitis.

RESULTS

Sensitivity and specificity to Streptococcus pneumoniae (n = 24) before and after optimizing threshold parameters were 79% and 52%, then 88% and 90%. Corresponding values for Neisseria meningitidis (n = 22) were 73% and 93%, then 67% and 100%, Listeria monocytogenes (n = 24) 21% and 100%, then 27% and 100%, and Haemophilus influenzae (n = 18) 56% and 100%, then 71% and 100%. A higher total sequencing depth, no antibiotic treatment prior to lumbar puncture, increased disease severity, and higher c-reactive protein levels were associated with pathogen detection.

CONCLUSION

We provide proof of principle that a viromic approach can be used to correctly identify bacterial ribosomal RNA in patients with bacterial meningitis. Further work should focus on increasing assay sensitivity, especially for problematic species (e.g. L. monocytogenes), as well as profiling additional pathogens. The technique is most suited to research settings and examination of idiopathic cases, rather than an acute clinical setting.

3D blood-brain barrier-organoids as a model for Lyme neuroborreliosis highlighting genospecies dependent organotropism

Lyme neuroborreliosis (LNB), a tick-borne infection caused by spirochetes within the Borrelia burgdorferi sensu lato (s.L.) complex, is among the most prevalent bacterial central nervous system (CNS) infections in Europe and the US. Here we have screened a panel of low-passage B. burgdorferi s.l. isolates using a novel, human-derived 3D blood-brain barrier (BBB)-organoid model. We show that human-derived BBB-organoids support the entry of Borrelia spirochetes, leading to swelling of the organoids and a loss of their structural integrity. The use of the BBB-organoid model highlights the organotropism between B. burgdorferi s.l. genospecies and their ability to cross the BBB contributing to CNS infection.

Bovine neutrophil chemotaxis to Listeria monocytogenes in neurolisteriosis depends on microglia-released rather than bacterial factors

BACKGROUND

Listeria monocytogenes (Lm) is a bacterial pathogen of major concern for humans and ruminants due to its neuroinvasive potential and its ability to cause deadly encephalitis (neurolisteriosis). On one hand, polymorphonuclear neutrophils (PMN) are key players in the defense against Lm, but on the other hand intracerebral infiltration with PMN is associated with significant neural tissue damage. Lm-PMN interactions in neurolisteriosis are poorly investigated, and factors inducing PMN chemotaxis to infectious foci containing Lm in the central nervous system (CNS) remain unidentified.

METHODS

In this study, we assessed bovine PMN chemotaxis towards Lm and supernatants of infected endogenous brain cell populations in ex vivo chemotaxis assays, to identify chemotactic stimuli for PMN chemotaxis towards Lm in the brain. In addition, microglial secretion of IL-8 was assessed both ex vivo and in situ.

RESULTS

Our data show that neither Lm cell wall components nor intact bacteria elicit chemotaxis of bovine PMN ex vivo. Moreover, astrocytes and neural cells fail to induce bovine PMN chemotaxis upon infection. In contrast, supernatant from Lm infected microglia readily induced chemotaxis of bovine PMN. Microglial expression and secretion of IL-8 was identified during early Lm infection in vitro and in situ, although IL-8 blocking with a specific antibody could not abrogate PMN chemotaxis towards Lm infected microglial supernatant.

CONCLUSIONS

These data provide evidence that host-derived rather than bacterial factors trigger PMN chemotaxis to bacterial foci in the CNS, that microglia have a primary role as initiators of bovine PMN chemotaxis into the brain during neurolisteriosis and that blockade of these factors could be a therapeutic target to limit intrathecal PMN chemotaxis and PMN associated damage in neurolisteriosis.

Listeria monocytogenes-How This Pathogen Uses Its Virulence Mechanisms to Infect the Hosts

Listeriosis is a serious food-borne illness, especially in susceptible populations, including children, pregnant women, and elderlies. The disease can occur in two forms: non-invasive febrile gastroenteritis and severe invasive listeriosis with septicemia, meningoencephalitis, perinatal infections, and abortion. Expression of each symptom depends on various bacterial virulence factors, immunological status of the infected person, and the number of ingested bacteria. Internalins, mainly InlA and InlB, invasins (invasin A, LAP), and other surface adhesion proteins (InlP1, InlP4) are responsible for epithelial cell binding, whereas internalin C (InlC) and actin assembly-inducing protein (ActA) are involved in cell-to-cell bacterial spread. L. monocytogenes is able to disseminate through the blood and invade diverse host organs. In persons with impaired immunity, the elderly, and pregnant women, the pathogen can also cross the blood-brain and placental barriers, which results in the invasion of the central nervous system and fetus infection, respectively. The aim of this comprehensive review is to summarize the current knowledge on the epidemiology of listeriosis and L. monocytogenes virulence mechanisms that are involved in host infection, with a special focus on their molecular and cellular aspects. We believe that all this information is crucial for a better understanding of the pathogenesis of L. monocytogenes infection.

Complications Associated with Foodborne Listeriosis: A Scoping Review

Listeria monocytogenes is a relatively rare but highly pathogenic bacterium that can cause foodborne infections. In the United States there are ∼1600 cases per year, 94% of which result in hospitalizations and 20% in deaths. Per-case burden is high because the disease also causes serious complications, including sepsis, encephalitis, meningitis, miscarriage, and stillbirth. The disease burden of L. monocytogenes is underestimated because some of these acute complications can also result in long-term outcomes. In this article, we conducted a scoping review of L. monocytogenes complications and longer term outcomes from articles published between 2000 and 2018. Search terms were developed for four major databases (PubMed, Scopus, Web of Science, and Embase) as well as gray literature and hand searches of review articles. We follow standard scoping review methodology and assessment. Out of 10,618 unique articles originally identified, 115 articles were included, representing 49 unique outcomes. The majority of studies were cohort designs (n = 67) and conducted in the United States or Europe (n = 98). Four major outcome groupings were death, neurological disorders, sepsis, and congenital infection. This study identifies substantial research on the common acute complications of L. monocytogenes and few long-term consequences of L. monocytogenes. We identify the need for additional studies to determine the longer term impacts of these acute complications.

Different Involvement of Vimentin during Invasion by Listeria monocytogenes at the Blood–Brain and the Blood–Cerebrospinal Fluid Barriers In Vitro

The human central nervous system (CNS) is separated from the blood by distinct cellular barriers, including the blood–brain barrier (BBB) and the blood–cerebrospinal fluid (CFS) barrier (BCSFB). Whereas at the center of the BBB are the endothelial cells of the brain capillaries, the BCSFB is formed by the epithelium of the choroid plexus. Invasion of cells of either the BBB or the BCSFB is a potential first step during CNS entry by the Gram-positive bacterium Listeria monocytogenes (Lm). Lm possesses several virulence factors mediating host cell entry, such as the internalin protein family—including internalin (InlA), which binds E-cadherin (Ecad) on the surface of target cells, and internalin B (InlB)—interacting with the host cell receptor tyrosine kinase Met. A further family member is internalin (InlF), which targets the intermediate filament protein vimentin. Whereas InlF has been shown to play a role during brain invasion at the BBB, its function during infection at the BCSFB is not known. We use human brain microvascular endothelial cells (HBMEC) and human choroid plexus epithelial papilloma (HIBCPP) cells to investigate the roles of InlF and vimentin during CNS invasion by Lm. Whereas HBMEC present intracellular and surface vimentin (besides Met), HIBCPP cells do not express vimentin (except Met and Ecad). Treatment with the surface vimentin modulator withaferin A (WitA) inhibited invasion of Lm into HBMEC, but not HIBCPP cells. Invasion of Lm into HBMEC and HIBCPP cells is, however, independent of InlF, since a deletion mutant of Lm lacking InlF did not display reduced invasion rates.

Listerial Meningitis and Brain Abscess With Coexisting COVID-19 Infection in a Young, Immunocompetent Male: A Case Report

Listeria monocytogenes (LM) is a gram-positive intracellular pathogen that can cause central nervous system infections such as meningitis, meningoencephalitis, rhombencephalitis, or cerebritis. It rarely causes a brain abscess. Listerial meningitis and brain abscess most commonly occur in immunocompromised individuals, neonates, pregnant females, alcoholics, and the elderly. We present a unique case of a young immunocompetent male who presented with listerial meningitis and brain abscess. Coexisting coronavirus disease 2019 (COVID-19) infection was also present. Since LM was not included in the differentials, the standard antibiotic regimen started for the meningitis therapy was ineffective. Remdesivir was administered to treat the coexisting COVID-19 infection. When the lumbar tap polymerase chain reaction pointed out that the causative agent was Listeria, we shifted to ampicillin and gentamicin therapy, to which the patient responded very effectively.LM is an atypical cause of meningitis and brain abscesses. A high index of suspicion is therefore required for early detection and effective treatment of listerial meningitis and brain abscess.

A subtractive proteomics and immunoinformatics approach towards designing a potential multi-epitope vaccine against pathogenic Listeriamonocytogenes

Listeria monocytogenes is the causative agent of listeriosis, which is dangerous for pregnant women, the elderly or individuals with a weakened immune system. Individuals with leukaemia, cancer, HIV/AIDS, kidney transplant and steroid therapy suffer from immunological damage are menaced. World Health Organization (WHO) reports that human listeriosis has a high mortality rate of 20-30% every year. To date, no vaccine is available to treat listeriosis. Thereby, it is high time to design novel vaccines against L. monocytogenes. Here, we present computational approaches to design an antigenic, stable and safe vaccine against the L. monocytogenes that could help to control the infections associated with the pathogen. Three vital pathogenic proteins of L. monocytogenes, such as Listeriolysin O (LLO), Phosphatidylinositol-specific phospholipase C (PI-PLC), and Actin polymerization protein (ActA), were selected using a subtractive proteomics approach to design the multi-epitope vaccine (MEV). A total of 5 Cytotoxic T-lymphocyte (CTL) and 9 Helper T-lymphocyte (HTL) epitopes were predicted from these selected proteins. To design the multi-epitope vaccine (MEV) from the selected proteins, CTL epitopes were joined with the AAY linker, and HTL epitopes were joined with the GPGPG linker. Additionally, a human β-defensin-3 (hBD-3) adjuvant was added to the N-terminal side of the final MEV construct to increase the immune response to the vaccine. The final MEV was predicted to be antigenic, non-allergen and non-toxic in nature. Physicochemical property analysis suggested that the MEV construct is stable and could be easily purified through the E. coli expression system. This in-silico study showed that MEV has a robust binding interaction with Toll-like receptor 2 (TLR2), a key player in the innate immune system. Current subtractive proteomics and immunoinformatics study provides a background for designing a suitable, safe and effective vaccine against pathogenic L. monocytogenes.

Current understanding of the human microbiome in glioma

There is mounting evidence that the human microbiome is highly associated with a wide variety of central nervous system diseases. However, the link between the human microbiome and glioma is rarely noticed. The exact mechanism of microbiota to affect glioma remains unclear. Recent studies have demonstrated that the microbiome may affect the development, progress, and therapy of gliomas, including the direct impacts of the intratumoral microbiome and its metabolites, and the indirect effects of the gut microbiome and its metabolites. Glioma-related microbiome (gut microbiome and intratumoral microbiome) is associated with both tumor microenvironment and tumor immune microenvironment, which ultimately influence tumorigenesis, progression, and responses to treatment. In this review, we briefly summarize current knowledge regarding the role of the glioma-related microbiome, focusing on its gut microbiome fraction and a brief description of the intratumoral microbiome, and put forward the prospects in which microbiome can be applied in the future and some challenges still need to be solved.

Listeria monocytogenes Pathogenesis: The Role of Stress Adaptation

Adaptive stress tolerance responses are the driving force behind the survival ability of Listeria monocytogenes in different environmental niches, within foods, and ultimately, the ability to cause human infections. Although the bacterial stress adaptive responses are primarily a necessity for survival in foods and the environment, some aspects of the stress responses are linked to bacterial pathogenesis. Food stress-induced adaptive tolerance responses to acid and osmotic stresses can protect the pathogen against similar stresses in the gastrointestinal tract (GIT) and, thus, directly aid its virulence potential. Moreover, once in the GIT, the reprogramming of gene expression from the stress survival-related genes to virulence-related genes allows L. monocytogenes to switch from an avirulent to a virulent state. This transition is controlled by two overlapping and interlinked transcriptional networks for general stress response (regulated by Sigma factor B, (SigB)) and virulence (regulated by the positive regulatory factor A (PrfA)). This review explores the current knowledge on the molecular basis of the connection between stress tolerance responses and the pathogenesis of L. monocytogenes. The review gives a detailed background on the currently known mechanisms of pathogenesis and stress adaptation. Furthermore, the paper looks at the current literature and theories on the overlaps and connections between the regulatory networks for SigB and PrfA.

Pearls & Oy-sters: Diagnosis and Subtyping of Listeria Ventriculitis in an Immunocompetent Host

Listeria monocytogenes is a gram-positive food-borne pathogen that causes gastrointestinal symptoms and central nervous system (CNS) infection in susceptible hosts.. Two lineages of Listeria cause the majority of neurolisteriosis in humans. In this report, we discuss a case of a 23-year-old previously healthy female who presented with acute-onset rapidly progressive altered mental status after eating undercooked meats at a local restaurant. Given her age and lack of comorbidities, bacterial meningitis was suspected, and she was treated with ceftriaxone, vancomycin, and steroids. Magnetic resonance imaging of the brain was consistent with meningitis and ventriculitis; Cerebrospinal fluid (CSF) analysis also suggested bacterial meningitis. Despite mechanical ventilation, pressors, and ventricular drain placement, she quickly decompensated and died 12 hours after arrival. CSF culture later returned positive for Listeria monocytogenes We used whole genome sequencing and near-source comparison to identify the Listeria subtype that led to her unexpected presentation. The results suggest that her CSF isolate was consistent with a lineage II Listeria serotype, which is known to exhibit greater genetic variation than the more commonly isolated lineage I serotypes. We conclude the discussion with diagnostic and treatment approaches to neurolisteriosis. In susceptible hosts, namely immunocompromised, pregnant, neonatal or elderly patients, Listeria infection may result in CNS invasion, causing meningoencephalitis and, rarely, ventriculitis and rhombencephalitis. Although neurolisteriosis most commonly affects individuals with known risk factors, CNS infection is nevertheless possible in otherwise healthy young patients. Suspicion should be raised in patients with an exposure history and do not improve with empiric antibiotics.

Neuropathological Characterization of Dolphin Morbillivirus Infection in Cetaceans Stranded in Italy

Simple Summary

There is abundant literature reporting demyelination in dogs and pinnipeds affected by morbillivirus infection, but myelinopathy is poorly investigated in stranded cetaceans affected with the virus. Also, the neuropathogenesis of cetacean morbillivirus infection has not been fully clarified, leaving questions on cell tropism unanswered. A novel dolphin morbillivirus lineage of Atlantic origin circulating in Italian waters replaced the previous Mediterranean strain in late 2015; however, differences in virulence and pathogenesis between the two strains have not yet been documented. The aims of the present study were to: describe histopathological changes and immunohistochemical findings in the central nervous system of 31 cetaceans which tested positive on molecular investigations for the two dolphin morbillivirus strains; characterize by double indirect immunofluorescence staining the areas of myelin damage. The most frequently observed morbillivirus-associated lesions were astro-microgliosis, neuronal necrosis, spongiosis, malacia, and non-suppurative meningoencephalitis. Demyelination was detected by means of a specific myelin biomarker. Inside and around the demyelinated areas there were morbillivirus antigen-bearing cells of mainly neuronal and microglial origin, associated with marked astro and microglia reactivity. Molecular and immunohistochemical analysis suggested a higher neurotropic affinity of the novel circulating strain.

Abstract

Cetacean morbillivirus (CeMV) is responsible for epidemic and endemic fatalities in free-ranging cetaceans. Neuro-inflammation sustained by CeMV is a leading cause of death in stranded cetaceans. A novel dolphin morbillivirus (DMV) strain of Atlantic origin circulating in Italian waters since early 2016 has caused acute/subacute lesions associated with positive immunolabelling of the virus. To date, myelin damage has not been fully documented and investigated in cetaceans. This study describes neuropathological findings in the brain tissue of 31 cetaceans found stranded along the Italian coastline and positive for DMV infection on molecular testing. Cell changes in the areas of myelinopathy were revealed by double indirect immunofluorescence. The most frequent DMV-associated lesions were astro-microgliosis, neuronal necrosis, spongiosis, malacia, and non-suppurative meningoencephalitis. Myelin reduction and areas of demyelination were revealed by means of a specific myelin biomarker. Morbilliviral antigen immunolabelling was mainly observed in neurons and microglial cells, in association with a marked activation of microglia and astrocytes. These findings extend our knowledge of DMV-associated brain lesions and shed light on their pathogenesis.

Interleukin-17A Contributed to the Damage of Blood-CNS Barriers During Streptococcus suis Meningitis

Streptococcus suis (S. suis) is an emerging zoonotic agent that can cause meningitis in humans with high mortality and morbidity. Meningitic S. suis can induce higher level of IL-17 than non-meningitic S. suis. Besides, IL-17A plays various roles on bacterial clearance or disruption of blood-CNS barriers through the downregulation and reorganization of tight junction (TJ) molecules. However, it remains to be elucidated for the role of IL-17A on the infection with meningitic S. suis. Here, we found that meningitic S. suis infection could not only cause acute death due to the damage of multiple organs, but also cause meningitis and clinical nervous signs since 60 h of post-infection due to the penetration of blood-CNS barriers after lasting bacteremia. In contrast, the mice with deficiency of il17a gene could not significantly change the acute inflammatory response and acute death, but it could not show obvious meningitis and clinical nervous signs caused by the meningitic S. suis infection. In addition, we also found that IL-17A could inhibit the transcription and expression of TJ proteins that facilitated the leakage of blood-CNS barriers since 60 h of post-infection during meningitic S. suis infection. Thus, our findings demonstrated that IL-17A could downregulate TJ proteins, which undoubtedly facilitated the leakage of blood-CNS barriers for bacterial invasion and then caused S. suis meningitis, providing potential targets for future prevention and treatment of this disease.

Listeria monocytogenes at the interface between ruminants and humans: A comparative pathology and pathogenesis review

The bacterium Listeria monocytogenes (Lm) is widely distributed in the environment as a saprophyte, but may turn into a lethal intracellular pathogen upon ingestion. Invasive infections occur in numerous species worldwide, but most commonly in humans and farmed ruminants, and manifest as distinct forms. Of those, neuroinfection is remarkably threatening due to its high mortality. Lm is widely studied not only as a pathogen but also as an essential model for intracellular infections and host-pathogen interactions. Many aspects of its ecology and pathogenesis, however, remain unclear and are rarely addressed in its natural hosts. This review highlights the heterogeneity and adaptability of Lm by summarizing its association with the environment, farm animals, and disease. It also provides current knowledge on key features of the pathology and (molecular) pathogenesis of various listeriosis forms in naturally susceptible species with a special focus on ruminants and on the neuroinvasive form of the disease. Moreover, knowledge gaps on pathomechanisms of listerial infections and relevant unexplored topics in Lm pathogenesis research are highlighted.

Pathogenicity and virulence of Listeria monocytogenes: A trip from environmental to medical microbiology

Listeria monocytogenes is a saprophytic gram-positive bacterium, and an opportunistic foodborne pathogen that can produce listeriosis in humans and animals. It has evolved an exceptional ability to adapt to stress conditions encountered in different environments, resulting in a ubiquitous distribution. Because some food preservation methods and disinfection protocols in food-processing environments cannot efficiently prevent contaminations, L. monocytogenes constitutes a threat to human health and a challenge to food safety. In the host, Listeria colonizes the gastrointestinal tract, crosses the intestinal barrier, and disseminates through the blood to target organs. In immunocompromised individuals, the elderly, and pregnant women, the pathogen can cross the blood-brain and placental barriers, leading to neurolisteriosis and materno-fetal listeriosis. Molecular and cell biology studies of infection have proven L. monocytogenes to be a versatile pathogen that deploys unique strategies to invade different cell types, survive and move inside the eukaryotic host cell, and spread from cell to cell. Here, we present the multifaceted Listeria life cycle from a comprehensive perspective. We discuss genetic features of pathogenic Listeria species, analyze factors involved in food contamination, and review bacterial strategies to tolerate stresses encountered both during food processing and along the host's gastrointestinal tract. Then we dissect host-pathogen interactions underlying listerial pathogenesis in mammals from a cell biology and systemic point of view. Finally, we summarize the epidemiology, pathophysiology, and clinical features of listeriosis in humans and animals. This work aims to gather information from different fields crucial for a comprehensive understanding of the pathogenesis of L. monocytogenes.

Cerebral Abscess Caused by Listeria monocytogenes: Case Report and Literature Review

BACKGROUND

 Listeria monocytogenes is an opportunistic gram-positive, facultative intracellular bacterium that causes invasive diseases mostly in pregnant women and immunosuppressed patients. Despite the predilection toward the central nervous system (CNS), it usually causes meningitis and meningoencephalitis, whereas brain abscesses are very uncommon.

CASE PRESENTATION

 We describe the case of a 69-year-old homeless patient with a brain abscess due to L. monocytogenes who was successfully treated surgically by a guided stereotactic aspiration and antibiotic therapy with ampicillin and gentamicin. Our patient was discharged after 4 weeks of therapy without neurologic deficits. Additionally, we provide a review of the literature of brain abscesses caused by L. monocytogenes.

CONCLUSIONS

 This case highlights the need to drain cerebral abscesses and culture pus to correctly treat patients with antibiotics, especially given the high mortality rate of this infectious entity.

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

Listeria monocytogenes crossing the blood-brain barrier in the form of "Trojan Horse" is of great significance for the establishment of bacterial encephalitis and meningitis. Induction of cell migration and crossing the blood-brain barrier is very important to understand the Listeria pathogenesis. The Rho GTPases family is considered a key factor in regulating cell migration. This study was designed to investigate the expression of Rho GTPases and their effect on the behavior of cell migration and the stimulation of immune factors. Selective Rho GTPases were investigated by real-time PCR and Western blot. Among these, the expression of RhoA was significantly increased following the infection of Listeria monocytogenes in macrophages. Further, we found that RhoA improves the migration of macrophages and expression of IL-1β, IL-6, and TNF-α. The expression of IL-1β, IL-6 and TNF-α possibly facilitates the migration and adhesion of macrophages to cross the blood-brain barrier. This study provides preliminary ground to investigate the detailed mechanism of Listeria monocytogenes crossing the blood-brain barrier.

Brain abscess due to listeria monocytogenes: A case report and literature review

RATIONALE

Listeria monocytogenes infective encephalitis is a rare phenomenon, which is more common in people with changed eating habits and immunodeficiency. To the best of our knowledge, listeria brain abscess is even more rare. In this case report, we summarized the clinical characteristics of listeria brain abscess, in order to explore the diagnosis and treatment of Listeria brain abscess, and raise awareness and attention to the disease.

PATIENT CONCERNS

A 64-years-old female patient presented to our institution with 4 days of right arm and leg weakness, the salient past history of the patient was nephrotic syndrome, membranous nephropathy diagnosed 6 months prior, for which she was prescribed glucocorticoids and cyclophosphamide.

DIAGNOSIS

Listeria monocytogenes was cultured in the blood of the patient. Comprehensive medical history and imaging features, she was diagnosed as listeria brain abscess.

INTERVENTIONS

The patient underwent ampicillin combined with meropenem but not surgery.

OUTCOMES

The patient recovered without complications. At a 3-month follow-up visit, the condition was better than that before treatment.

LESSONS

Listeria brain abscess is an unusual form of listeriosis, its clinical manifestations lack specificity. Early accurate diagnosis and standardized treatment can effectively promote the recovery of neurological function as well as reduce the morbidity and mortality and improve the prognosis.

Infectious disease-associated encephalopathies

Infectious diseases may affect brain function and cause encephalopathy even when the pathogen does not directly infect the central nervous system, known as infectious disease-associated encephalopathy. The systemic inflammatory process may result in neuroinflammation, with glial cell activation and increased levels of cytokines, reduced neurotrophic factors, blood-brain barrier dysfunction, neurotransmitter metabolism imbalances, and neurotoxicity, and behavioral and cognitive impairments often occur in the late course. Even though infectious disease-associated encephalopathies may cause devastating neurologic and cognitive deficits, the concept of infectious disease-associated encephalopathies is still under-investigated; knowledge of the underlying mechanisms, which may be distinct from those of encephalopathies of non-infectious cause, is still limited. In this review, we focus on the pathophysiology of encephalopathies associated with peripheral (sepsis, malaria, influenza, and COVID-19), emerging therapeutic strategies, and the role of neuroinflammation.

Neonatal susceptibility to meningitis results from the immaturity of epithelial barriers and gut microbiota

Neonates are highly susceptible to bacterial meningitis as compared to children and adults. Group B streptococcus (GBS) is a major cause of neonatal meningitis. Neonatal meningitis can result from GBS intestinal colonization and translocation across the intestinal barrier (IB). Here, we show that the immaturity of the neonatal intestinal microbiota leads to low resistance to GBS intestinal colonization and permissiveness of the gut-vascular barrier. Moreover, the age-dependent but microbiota-independent Wnt activity in intestinal and choroid plexus (CP) epithelia results in a lower degree of cell-cell junctions' polarization, which favors bacterial translocation. This study thus reveals that neonatal susceptibility to GBS meningitis results from the age-dependent immaturity of the intestinal microbiota and developmental pathways associated with neonatal tissue growth, which both concur to GBS gut colonization, systemic dissemination, and neuroinvasion. Whereas the activation of developmental pathways is intrinsic to neonates, interventions aimed at maturing the microbiota may help prevent neonatal meningitis.

Expression of Acute Phase Protein, Glial Fibrillary Acidic Protein, Epithelial Cadherin, and S100 Protein in Brain Tissues from Natural Cases of Ovine Encephalitic Listeriosis

Listeriosis is a disease that is induced by infection with the Gram-positive bacterium Listeria monocytogenes. Much is still unknown about the pathogenesis of encephalitic listeriosis. We aimed to identify the contribution of glial fibrillary acidic protein (GFAP), epithelial cadherin (E-cadherin), S100, and acute-phase proteins (APPs) in pathogenesis, clinical and preclinical diagnosis of natural cases of encephalitic listeriosis. Of 1,325 Ossimi sheep, 64 were suspected of having listeriosis from 2018 to 2020. Prospective cohort evaluation of clinical and postmortem findings was performed, in addition to bacterial isolation, the measurement of APPs in serum and cerebrospinal fluid (CSF), and the histopathological and immunohistochemical evaluation of GFAP, S100, and E-cadherin. Infected sheep showed nervous symptoms ranging from neck stretching to complete paralysis. APPs were significantly increased in the CSF of both clinically and preclinically diseased animals; however, serum APPs were only significantly increased in clinically diseased animals. Histopathological evaluation revealed microabscesses, meningoencephalitis, and perivascular cuffing of the brainstem of infected sheep. Immunohistochemical investigations revealed strong expression of GFAP and S100 in necrotic areas and negative expression of E-cadherin. The measurement of CSF APPs could be useful in the preclinical diagnosis of sheep listeriosis. GFAP and S100 proteins could be involved in the pathogenesis of listeriosis; however, E-cadherin does not appear to be involved.

Plasma-Treated Water Affects Listeria monocytogenes Vitality and Biofilm Structure

Background: Plasma-generated compounds (PGCs) such as plasma-processed air (PPA) or plasma-treated water (PTW) offer an increasingly important alternative for the control of microorganisms in hard-to-reach areas found in several industrial applications including the food industry. To this end, we studied the antimicrobial capacity of PTW on the vitality and biofilm formation of Listeria monocytogenes, a common foodborne pathogen. Results: Using a microwave plasma (MidiPLexc), 10 ml of deionized water was treated for 100, 300, and 900 s (pre-treatment time), after which the bacterial biofilm was exposed to the PTW for 1, 3, and 5 min (post-treatment time) for each pre-treatment time, separately. Colony-forming units (CFU) were significantly reduced by 4.7 log10 ± 0.29 log10, as well as the metabolic activity decreased by 47.9 ± 9.47% and the cell vitality by 69.5 ± 2.1%, compared to the control biofilms. LIVE/DEAD staining and fluorescence microscopy showed a positive correlation between treatment and incubation times, as well as reduction in vitality. Atomic force microscopy (AFM) indicated changes in the structure quality of the bacterial biofilm. Conclusion: These results indicate a promising antimicrobial impact of plasma-treated water on Listeria monocytogenes, which may lead to more targeted applications of plasma decontamination in the food industry in the future.

Rhombencephalitis due to Listeria monocytogenes infection with GQ1b antibody positivity and multiple intracranial hemorrhage: a case report and literature review

Listeria monocytogenes is a Gram-positive facultative intracellular bacterium that causes central nervous system infection. We report a case of rhombencephalitis caused by L. monocytogenes infection, which mimicked Bickerstaff’s brainstem encephalitis, and GQ1b antibody positivity and multiple intracranial foci were observed. A 68-year-old male patient presented with a nonspecific prodrome of faintness, forehead tightness, and walking instability. This was followed by progressive cranial nerve palsies, limb weakness, cerebellar signs, hyperpyrexia, and impaired consciousness. Brain imaging showed multiple abnormal brainstem and cerebellar signals that were accompanied by blood infiltration without any lesion enhancement. Serum GQ1b antibody positivity led to an initial diagnosis of Bickerstaff’s brainstem encephalitis, which was treated with immunosuppressive therapy with limited efficacy. A pathogen examination helped confirm L. monocytogenes infection. A combination of meropenem and trimethoprim-sulfamethoxazole therapy was applied and the patient recovered without sequelae. The symptoms and imaging of Listeria rhombencephalitis are nonspecific. Accurate diagnosis and prompt treatment of this condition are essential. Whether Listeria infection triggers an autoimmune response remains unclear.

COVID-19-Associated Acute Brain Dysfunction Related to Sepsis

In global term, as of November 30, 2020, over 30 million people has been infected by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and more than 10,000,000 of them died of acute organ failure. Our reviews have shown that coronavirus disease 2019 (COVID-19) patients with pneumonia and acute respiratory distress syndrome (ARDS) have life-threatening acute brain dysfunction (ABD), ranging from altered mental status/delirium to stupor/coma. Altered mental status/delirium was the most common manifestation of ABD caused by severe COVID-19. The prevalence of altered mental status and/or delirium was up to 66-79.5%, and prevalence of coma was 10%. The most common clinical type of COVID-19-associated ABD was COVID-19-associated acute stroke including ischemic and hemorrhagic stroke (n > 350 cases), followed by COVID-19-associated encephalopathy (n > 200 cases), and COVID-19-associated central nervous system (CNS) infection (n > 70 cases). According to the Sepsis-3 criteria, we confess that severe COVID-19-associated ABD with ARDS and altered mental status is related to sepsis. Moreover, we also review the diagnosis and treatment of COVID-19-associated ABD with sepsis. In view of the fact that COVID-19 is at the peak of epidemic worldwide, we hope that this review will provide evidence of COVID-19 sepsis threating to the brain dysunction. Thus, recognizing the COVID-19-associated ABD related to sepsis is very important for early empirical combination therapy to survive severe COVID-19.

Multifunctional Amyloids in the Biology of Gram-Positive Bacteria

Since they were discovered, amyloids have proven to be versatile proteins able to participate in a variety of cellular functions across all kingdoms of life. This multitask trait seems to reside in their ability to coexist as monomers, aggregates or fibrillar entities, with morphological and biochemical peculiarities. It is precisely this common molecular behaviour that allows amyloids to cross react with one another, triggering heterologous aggregation. In bacteria, many of these functional amyloids are devoted to the assembly of biofilms by organizing the matrix scaffold that keeps cells together. However, consistent with their notion of multifunctional proteins, functional amyloids participate in other biological roles within the same organisms, and emerging unprecedented functions are being discovered. In this review, we focus on functional amyloids reported in gram-positive bacteria, which are diverse in their assembly mechanisms and remarkably specific in their biological functions that they perform. Finally, we consider cross-seeding between functional amyloids as an emerging theme in interspecies interactions that contributes to the diversification of bacterial biology.

Innate immune responses to Listeria in vivo

Listeria monocytogenes (Lm) is a foodborne bacterial pathogen that causes listeriosis, a severe infection that manifests as bacteremia and meningo-encephalitis mostly in immunocompromised individuals, and maternal-fetal infection. A critical pathogenic determinant of Lm relies on its ability to actively cross the intestinal barrier, disseminate systemically and cross the blood-brain and placental barriers. Here we illustrate how Lm both evades innate immunity, favoring its dissemination in host tissues, and triggers innate immune defenses that participate to its control.

Pathogenic Differences of Type 1 Restriction-Modification Allele Variants in Experimental Listeria monocytogenes Meningitis

Background: L. monocytogenes meningoencephalitis has a mortality rate of up to 50% and neurofunctional sequelae are common. Type I restriction-modification systems (RMS) are capable of adding methyl groups to the host genome. Some contain multiple sequence recognition (hsdS) genes that recombine, resulting in distinct DNA methylation patterns and patterns of gene expression. These phenotypic switches have been linked to virulence and have recently been discovered in multiple clonal complexes of L. monocytogenes. In the present study, we investigated the significant of RMS on L. monocytogenes virulence during the acute phase of experimental meningitis. Methods: L. monocytogenes strains containing RMS systems were identified, and purified clones enriched for single hsdS alleles were isolated. In vivo, 11-day old Wistar rats were infected with an inoculum containing (a) one of 4 single RMS allele variants (A, B, C, D) treated with amoxicillin (AMX 50 mg/kg/dosis, q8h), (b) a mixture of all 4 variants with or without AMX treatment, or (c) different mixtures of 2 RMS allele variants. At selected time points after infection, clinical and inflammatory parameters, bacterial titers and brain damage were determined. Changes in the relative frequency of the occurring RMS alleles in the inoculum and in CSF or cerebellum of infected animals were analyzed by capillary electrophoresis. Results: We have identified a phase variable RMS locus within L. monocytogenes CC4 and generated stocks that stably expressed each of the possible hsdS genes within that loci. Generation of these allele variants (A, B, C, D) allowed us to determine the methylation pattern associated with each hsdS through SMRT sequencing. In vivo infections with these single allele variants revealed differences in disease severity in that C induced the worst clinical outcome and more pronounced hippocampal apoptosis; D showed the most pronounced weight loss and the highest bacterial titer in the cerebellum. A caused the least severe disease. Conclusion: We identified that L. monocytogenes expressing hsdS (A) causes less damage than when other hsdS genes are expressed. While expression of hsdSC and D worsened the outcome in L. monocytogenes meningitis. We also demonstrate a competitive advantage of variants C and B over variant A in this model. Phenotypical switching may therefore represent a mechanism of virulence regulation during the acute phase of CNS infections with L. monocytogenes.

In silico identification of novel PrfA inhibitors to fight listeriosis: A virtual screening and molecular dynamics studies

Listeria monocytogenes is considered to be one of the most dangerous foodborne pathogens as it can cause listeriosis, a life-threatening human disease. While the incidence of listeriosis is very low its fatality rate is exceptionally high. Because many multi-resistance Listeria monocytogenes strains that do not respond to conventional antibiotic therapy have been recently described, development of new antimicrobials to fight listeriosis is necessary. The positive regulatory factor A (PrfA) is a key homodimeric transcription factor that modulates the transcription of multiple virulence factors which are ultimately responsible of Listeria monocytogenes' pathogenicity. In the present manuscript we describe several new potential PrfA inhibitors that were identified after performing ligand-based virtual screening followed by molecular docking calculations against the wild-type PrfA structure. The three top-scored drug-likeness inhibitors bound to the wild-type PrfA structure were further assessed by Molecular Dynamics (MD) simulations. Besides, the three top-scored inhibitors were docked into a constitutive active apoPrfA mutant structure and the corresponding complexes were also simulated by MD. According to the obtained data, PUBChem 87534955 (P875) and PUBChem 58473762 (P584) may not only bind and inhibit wild-type PrfA but the aforementioned apoPrfA mutant as well. Therefore, P875 and P584 might represent good starting points for the development of a completely new set of antimicrobial agents to treat listeriosis.

Neurolisteriosis in a previously asymptomatic patient with serum IgM deficiency: a case report

BACKGROUND

Listeria monocytogenes is an opportunistic pathogen of the central nervous system commonly associated with impaired cell-mediated immunity. We hereby present a case of adult neurolisteriosis where the only immunological feature persistently present was serum IgM deficiency, suggesting that non-specific humoral immunity may also play a central role in the control of neuroinvasion by Listeria monocytogenes.

CASE PRESENTATION

A 62-year-old male who had never experienced severe infections presented with headache, nuchal rigidity and confusion. Neuroimaging was normal and lumbar puncture revealed pleiocytosis (760 leukocytes/mm3) and hypoglycorrhachia (34 mg/dL). The patient was treated empirically for bacterial meningitis. Indeed, further analysis of the CSF showed infection by Listeria monocytogenes, which was accompanied by reduced serum IgM levels that persisted well beyond the period of acute bacterial infection. Levels of IgG and IgA isotypes, along with peripheral blood counts of major leukocyte subsets, were at the same time largely preserved. Intriguingly, the absence of membrane-bound IgM on B cells was essentially complete in the acute post-infection period leading to a remarkable recovery after 12 months, suggesting that mechanisms other than defective membrane expression are underlying serum deficiency.

CONCLUSIONS

As far as we know, this is the first reported case of neurolisteriosis associated with IgM deficiency in an adult individual without a history of severe infections or other underlying conditions. A possible role of circulating IgM against invasive disease caused by Listeria monocytogenes, particularly in the early course of host-pathogen interaction, is discussed.

A listeriolysin O subunit vaccine is protective against Listeria monocytogenes

Listeria monocytogenes is a facultative intracellular pathogen responsible for the life-threatening disease listeriosis. The pore-forming toxin listeriolysin O (LLO) is a critical virulence factor that plays a major role in the L. monocytogenes intracellular lifecycle and is indispensable for pathogenesis. LLO is also a dominant antigen for T cells involved in sterilizing immunity and it was proposed that LLO acts as a T cell adjuvant. In this work, we generated a novel full-length LLO toxoid (LLO^T) in which the cholesterol-recognition motif, a threonine-leucine pair located at the tip of the LLO C-terminal domain, was substituted with two glycine residues. We showed that LLO^T lost its ability to bind cholesterol and to form pores. Importantly, LLO^T retained binding to the surface of epithelial cells and macrophages, suggesting that it could efficiently be captured by antigen-presenting cells. We then determined if LLO^T can be used as an antigen and adjuvant to protect mice from L. monocytogenes infection. Mice were immunized with LLO^T alone or together with cholera toxin or Alum as adjuvants. We found that mice immunized with LLO^T alone or in combination with the Th2-inducing adjuvant Alum were not protected against L. monocytogenes. On the other hand, mice immunized with LLO^T along with the experimental adjuvant cholera toxin, were protected against L. monocytogenes, as evidenced by a significant decrease in bacterial burden in the liver and spleen three days post-infection. This immunization regimen elicited mixed Th1, Th2, and Th17 responses, as well as the generation of LLO-neutralizing antibodies. Further, we identified T cells as being required for immunization-induced reductions in bacterial burden, whereas B cells were dispensable in our model of non-pregnant young mice. Overall, this work establishes that LLO^T is a promising vaccine antigen for the induction of protective immunity against L. monocytogenes by subunit vaccines containing Th1-driving adjuvants.