Characterization of a Listeria monocytogenes meningitis mouse model

Meningitis caused by Aeromonas hydrophila in Oreochromis niloticus: Proteomics and druggability of virulence factors

Meningitis caused by Gram-negative bacteria is a serious public health problem, causing morbidity and mortality in both children and adults. Here, we propose a novel experimental model using Nile tilapia (Oreochromis niloticus) to study neuroinflammation. The fish were infected with Aeromonas hydrophila, and the course of infection was monitored in the peripheral blood. Septicemia was obvious in the blood, while in the brain tissue, infection of the meninges was present. The histopathological examination showed suppurative meningitis, and the cellular immune response in the brain tissue during infection was mediated by microglia. These cells were morphologically characterized and phenotyped by MHC class II markers and CD68. The increased production of TNF-α, IL-1β and iNOS supported the infiltration of these cells during the neuroinflammatory process. In the proteomic analysis of A. hydrophila isolated from brain tissue, we found chemotactic and transport proteins, proteolytic enzymes and enzymes associated with the dismutation of nitric oxide (NO), as well as motor proteins and those responsible for cell division. After characterizing the most abundant proteins during the course of infection, we investigated the druggability index of these proteins and identified promising peptide sequences as molecular targets that are similar among bacteria. Thus, these findings deepened the understanding of the pathophysiology of meningitis caused by A. hydrophila. Moreover, through the proteomics analysis, important mechanisms and pathways used by the pathogen to subvert the host response were revealed, providing insights for the development of novel antibiotics and vaccines.

Genomic epidemiology of the clinically dominant clonal complex 1 in the Listeria monocytogenes population in the UK

Listeria monocytogenes is a food-borne pathogen, typically affecting the elderly, immunocompromised patients and pregnant women. The aim of this study was to determine the population structure of L. monocytogenes clonal complex 1 (CC1) in the UK and describe the genomic epidemiology of this clinically significant CC. We interrogated a working dataset of 4073 sequences of L. monocytogenes isolated between January 2015 and December 2020 from human clinical specimens, food and/or food-production environments. A minimum spanning tree was reconstructed to determine the population structure of L. monocytogenes in the UK. Subsequent analysis focused on L. monocytogenes CC1, as the cause of the highest proportion of invasive listeriosis in humans. Sequencing data was integrated with metadata on food and environmental isolates, and information from patient questionnaires, including age, sex and clinical outcomes. All isolates either belonged to lineage I (n=1299/4073, 32%) or lineage II (n=2774/4073, 68%), with clinical isolates from human cases more likely to belong to lineage I (n=546/928, 59%) and food isolates more likely to belong to lineage II (n=2352/3067, 77%). Of the four largest CCs, CC1 (n=237) had the highest proportion of isolates from human cases of disease (CC1 n=160/237, 67.5 %; CC121 n=13/843, 2 %; CC9 n=53/360, 15 %; CC2 n=69/339, 20%). Within CC1, most cases were female (n=95/160, 59%, P=0.01771) and the highest proportion of cases were in people >60 years old (39/95, 41%, P=1.314×10-6) with a high number of them aged 20-39 years old (n=35/95, 37%) most linked to pregnancy-related listeriosis (n=29/35, 83%). Most of the male cases were in men aged over 60 years old (40/65, 62%), and most of the fatal cases in both males and females were identified in this age group (42/55, 76%). Phylogenetic analysis revealed 23 5 SNP single linkage clusters comprising 80/237 (34 %) isolates with cluster sizes ranging from 2 to 19. Five 5 SNP clusters comprised isolates from human cases and an implicated food item. Expanding the analysis to 25 SNP single linkage clusters resolved an additional two clusters linking human cases to a potential food vehicle. Analysis of demographic and clinical outcome data identified CC1 as a clinically significant cause of invasive listeriosis in the elderly population and in women of child-bearing age. Phylogenetic analysis revealed the population structure of CC1 in the UK comprised small, sparsely populated genomic clusters. Only clusters containing isolates from an implicated food vehicle, or food processing or farming environments, were resolved, emphasizing the need for clinical, food and animal-health agencies to share sequencing data in real time, and the importance of a One Health approach to public-health surveillance of listeriosis.

A multi-arm, parallel, preclinical study investigating the potential benefits of acetazolamide, candesartan, and triciribine in combination with fluconazole for the treatment of cryptococcal meningoencephalitis

Cryptococcus neoformans, an opportunistic fungal pathogen, primarily infects immunodeficient patients frequently causing cryptococcal meningoencephalitis (CM). Increased intracranial pressure (ICP) is a serious complication responsible for increased morbidity and mortality in CM patients. Non-invasive pharmacological agents that mitigate ICP could be beneficial in treating CM patients. The objective of the study was to investigate the efficacy of acetazolamide (AZA), candesartan (CAN), and triciribine (TCBN), in combination with the antifungal fluconazole, on C. neoformans-induced endothelial, brain, and lung injury in an experimental mouse model of CM. Our study shows that C. neoformans increases the expression of brain endothelial cell (BEC) junction proteins Claudin-5 (Cldn5) and VE-Cadherin to induce pathological cell-barrier remodeling and gap formation associated with increased Akt and p38 MAPK activation. All three agents inhibited C. neoformans-induced endothelial gap formation, only CAN and TCBN significantly reduced C. neoformans-induced Cldn5 expression, and only TCBN was effective in inhibiting Akt and p38MAPK. Interestingly, although C. neoformans did not cause brain or lung edema in mice, it induced lung and brain injuries, which were significantly reversed by AZA, CAN, or TCBN. Our study provides novel insights into the direct effects of C. neoformans on BECs in vitro, and the potential benefits of using AZA, CAN, or TCBN in the management of CM patients.

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.

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.

Basidiocarp structures of Lentinus crinitus: an antimicrobial source against foodborne pathogens and food spoilage microorganisms

Lentinus crinitus basidiocarps are an alternative to antimicrobials, but the stipe (24% basidiocarp) is discarded even with potential antimicrobial activity. This study evaluated the antimicrobial activity of L. crinitus basidiocarp pileus and stipe extracts against foodborne pathogens and food spoilage microorganisms. Basidiocarps of L. crinitus were grown in sugarcane bagasse and rice husks and the pileus and stipe methanolic extract was analyzed by broth microdilution method for antimicrobial activity against eight bacteria and eight fungi. The minimum bactericidal concentration values for pileus and stipe ranged from 0.40 to 0.50 mg mL^- 1, for streptomycin from 0.10 to 0.50 mg mL^- 1, and for ampicillin from 0.40 to 1.20 mg mL^- 1. The minimum fungicidal concentration values for pileus and stipe ranged from 0.06 to 0.60 mg mL^- 1, for bifonazole from 0.20 to 0.25 mg mL^- 1, and for ketoconazole from 0.30 to 3.50 mg mL^- 1. Extracts had bacteriostatic, bactericidal, fungistatic and fungicidal activity against all microorganisms, but with greater efficiency and specificity for some microorganisms. Both pileus and stipe are promising and sustainable alternatives for use in food, agricultural, and pharmaceutical industries.

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.

Mint3 depletion-mediated glycolytic and oxidative alterations promote pyroptosis and prevent the spread of Listeria monocytogenes infection in macrophages

Listeria monocytogenes (LM) infection induces pyroptosis, a form of regulated necrosis, in host macrophages via inflammasome activation. Here, we examined the role of Mint3 in macrophages, which promotes glycolysis via hypoxia-inducible factor-1 activation, during the initiation of pyroptosis following LM infection. Our results showed that Mint3-deficient mice were more resistant to lethal listeriosis than wild-type (WT) mice. Additionally, the mutant mice showed higher levels of IL-1β/IL-18 in the peritoneal fluid during LM infection than WT mice. Moreover, ablation of Mint3 markedly increased the activation of caspase-1, maturation of gasdermin D, and pyroptosis in macrophages infected with LM in vitro, suggesting that Mint3 depletion promotes pyroptosis. Further analyses revealed that Mint3 depletion upregulates inflammasome assembly preceding pyroptosis via glycolysis reduction and reactive oxygen species production. Pharmacological inhibition of glycolysis conferred resistance to listeriosis in a Mint3-dependent manner. Moreover, Mint3-deficient mice treated with the caspase-1 inhibitor VX-765 were as susceptible to LM infection as WT mice. Taken together, these results suggest that Mint3 depletion promotes pyroptosis in host macrophages, thereby preventing the spread of LM infection. Mint3 may serve as a target for treating severe listeriosis by inducing pyroptosis in LM-infected macrophages.

Population structure-guided profiling of antibiotic resistance patterns in clinical Listeria monocytogenes isolates from Germany identifies pbpB3 alleles associated with low levels of cephalosporin resistance

Numbers of listeriosis illnesses have been increasing in Germany and the European Union during the last decade. In addition, reports on the occurrence of antibiotic resistance in Listeria monocytogenes in clinical and environmental isolates are accumulating. The susceptibility towards 14 antibiotics was tested in a selection of clinical L. monocytogenes isolates to get a more precise picture of the development and manifestation of antibiotic resistance in the L. monocytogenes population. Based on the population structure determined by core genome multi locus sequence typing (cgMLST) 544 out of 1220 sequenced strains collected in Germany between 2009 and 2019 were selected to cover the phylogenetic diversity observed in the clinical L. monocytogenes population. All isolates tested were susceptible towards ampicillin, penicillin and co-trimoxazole – the most relevant antibiotics in the treatment of listeriosis. Resistance to daptomycin and ciprofloxacin was observed in 493 (91%) and in 71 (13%) of 544 isolates, respectively. While all tested strains showed resistance towards ceftriaxone, their resistance levels varied widely between 4 mg/L and >128 mg/L. An allelic variation of the penicillin binding protein gene pbpB3 was identified as the cause of this difference in ceftriaxone resistance levels. This study is the first population structure-guided analysis of antimicrobial resistance in recent clinical isolates and confirms the importance of penicillin binding protein B3 (PBP B3) for the high level of intrinsic cephalosporin resistance of L. monocytogenes on a population-wide scale.

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.

Neurotropic Lineage III Strains of Listeria monocytogenes Disseminate to the Brain without Reaching High Titer in the Blood

Progress in understanding the two naturally occurring central nervous system (CNS) manifestations of listeriosis (meningitis/meningoencephalitis and rhombencephalitis) has been limited by the lack of small animal models that can readily distinguish between these distinct infections. We report here that certain neurotropic strains of Listeria monocytogenes can spread to the brains of young otherwise healthy mice and cause neurological deficits without causing a fatal bacteremia. The novel strains described here fall within phylogenetic lineage III, a small collection of L. monocytogenes isolates that have not been well characterized to date. The animal model reported here mimics many features of human rhombencephalitis and will be useful for studying the mechanisms that allow L. monocytogenes to disseminate to the brain stem following natural foodborne transmission.

Listeria monocytogenes is thought to colonize the brain using one of three mechanisms: direct invasion of the blood-brain barrier, transportation across the barrier by infected monocytes, and axonal migration to the brain stem. The first two pathways seem to occur following unrestricted bacterial growth in the blood and thus have been linked to immunocompromise. In contrast, cell-to-cell spread within nerves is thought to be mediated by a particular subset of neurotropic L. monocytogenes strains. In this study, we used a mouse model of foodborne transmission to evaluate the neurotropism of several L. monocytogenes isolates. Two strains preferentially colonized the brain stems of BALB/cByJ mice 5 days postinfection and were not detectable in blood at that time point. In contrast, infection with other strains resulted in robust systemic infection of the viscera but no dissemination to the brain. Both neurotropic strains (L2010-2198, a human rhombencephalitis isolate, and UKVDL9, a sheep brain isolate) typed as phylogenetic lineage III, the least characterized group of L. monocytogenes. Neither of these strains encodes InlF, an internalin-like protein that was recently shown to promote invasion of the blood-brain barrier. Acute neurologic deficits were observed in mice infected with the neurotropic strains, and milder symptoms persisted for up to 16 days in some animals. These results demonstrate that neurotropic L. monocytogenes strains are not restricted to any one particular lineage and suggest that the foodborne mouse model of listeriosis can be used to investigate the pathogenic mechanisms that allow L. monocytogenes to invade the brain stem.

IMPORTANCE Progress in understanding the two naturally occurring central nervous system (CNS) manifestations of listeriosis (meningitis/meningoencephalitis and rhombencephalitis) has been limited by the lack of small animal models that can readily distinguish between these distinct infections. We report here that certain neurotropic strains of Listeria monocytogenes can spread to the brains of young otherwise healthy mice and cause neurological deficits without causing a fatal bacteremia. The novel strains described here fall within phylogenetic lineage III, a small collection of L. monocytogenes isolates that have not been well characterized to date. The animal model reported here mimics many features of human rhombencephalitis and will be useful for studying the mechanisms that allow L. monocytogenes to disseminate to the brain stem following natural foodborne transmission.

Population Structure of Non-ST6 Listeria monocytogenes Isolated in the Red Meat and Poultry Value Chain in South Africa

Meat products have been implicated in many listeriosis outbreaks globally, however there is a dearth of information on the diversity of L. monocytogenes isolates circulating in food products in South Africa. The aim of this study was to investigate the population structure of L. monocytogenes isolated in the meat value chain within the South African market. Based on whole-genome sequence analysis, a total of 217 isolates were classified into two main lineage groupings namely lineages I (n = 97; 44.7%) and II (n = 120; 55.3%). The lineage groups were further differentiated into IIa (n = 95, 43.8%), IVb (n = 69, 31.8%), IIb (n = 28, 12.9%), and IIc (n = 25, 11.5%) sero-groups. The most abundant sequence types (STs) were ST204 (n = 32, 14.7%), ST2 (n = 30, 13.8%), ST1 (n = 25, 11.5%), ST9 (n = 24, 11.1%), and ST321 (n = 21, 9.7%). In addition, 14 clonal complex (CCs) were identified with over-representation of CC1, CC3, and CC121 in "Processed Meat-Beef", "RTE-Poultry", and "Raw-Lamb" meat categories, respectively. Listeria pathogenic islands were present in 7.4% (LIPI-1), 21.7% (LIPI-3), and 1.8% (LIPI-4) of the isolates. Mutation leading to premature stop codons was detected in inlA virulence genes across isolates identified as ST121 and ST321. The findings of this study demonstrated a high-level of genomic diversity among L. monocytogenes isolates recovered across the meat value chain control points in South Africa.

Retrospective Study of Listeria Monocytogenes Isolated in the Territory of Inner Eurasia from 1947 to 1999

Listeriosis is one of the most significant humans and animals foodborne infectious diseases. Here, we characterized 48 Listeria monocytogenes strains isolated in the territory of inner Eurasia during the second half of the 20th century. A total of 23 strains (52.3%) were susceptible to the nine antibiotics tested, 30.43%, 15.22%, and 8.7% were resistant penicillin G, ampicillin, and enrofloxacin, respectively. We applied the multilocus sequence typing (MLST) scheme to determine the phylogenetic positions of the strains. All but one strain belonged to the II phylogenetic lineage, and the majority of the strains belonged to one of the previously described clonal complexes (СCs). More than 60% of the strains belonged to the clonal complex CC7 that prevailed among all sources, including cattle (58%), small ruminants (64%), rodents (71%), and humans (50%). Further, CC7, CC101, and CC124 were found among human isolates. The MLST scheme was supplemented with virulence gene analysis. In total, eight inlA, six inlB, and six inlC allelic variants were found, and all but one strain carried one of the two inlE alleles. Most strains (62.5%) belonged to the same multivirulence locus sequence typing (MvLST) type, which includes CC7, inlA allele 4, inlB allele 14, inlC allele 6, and inlE allele 8.

Past and Current Perspectives in Modeling Bacteria and Blood-Brain Barrier Interactions

The central nervous system (CNS) barriers are highly specialized cellular barriers that promote brain homeostasis while restricting pathogen and toxin entry. The primary cellular constituent regulating pathogen entry in most of these brain barriers is the brain endothelial cell (BEC) that exhibits properties that allow for tight regulation of CNS entry. Bacterial meningoencephalitis is a serious infection of the CNS and occurs when bacteria can cross specialized brain barriers and cause inflammation. Models have been developed to understand the bacterial - BEC interaction that lead to pathogen crossing into the CNS, however, these have been met with challenges due to these highly specialized BEC phenotypes. This perspective provides a brief overview and outlook of the in vivo and in vitro models currently being used to study bacterial brain penetration, and opinion on improved models for the future.

The TRAPs From Microglial Vesicles Protect Against Listeria Infection in the CNS

Previous studies have demonstrated that T cells and microglia could fight against cerebral Listeria monocytogenes (Listeria); however, their synergistic anti-Listeria mechanisms remain unknown. Following Listeria infection in a culture system, we found that microglia, but not nerve cells, could release extracellular traps (ETs) which originated from microglial vesicles. Specific inhibitor analysis showed that extracellular DNA (eDNA), matrix metallopeptidases (MMP9 and MMP12), citrullinated histone H3, and peptidyl arginine deiminase 2 were the major components of microglial ETs (MiETs) and were also the components of vesicles. Systematic analysis indicated that Listeria-induced MiETs were cytosolic reactive oxygen species (ROS)- and NADPH oxidase (NOX)-dependent and involved ERK. MiETs were exhibited in Listeria-infected mouse brain and might protected against Listeria infection via bacterial killing in a mouse meningitis model, and MiETs existed in cerebrospinal fluid (CSF) from Listeria meningitis patients in vivo and in vitro. Additionally, interferon-γ could induce MiET formation in Listeria-infected microglia in vitro that was mediated by NOX, and there was a positive relationship between the elevated level of IFN-γ and eDNA and nucleosomes in the brain homogenates and CSF of Listeria meningitis model mice and in the CSF before treatment in clinical Listeria meningitis patients. Together, this is the first report of MiET formation, these findings pave the way for deeper exploration of the innate immune response to pathogens in CNS.