The Pathogenic Role of Anti-Granulocyte-Macrophage Colony-Stimulating Factor Autoantibodies in the Nocardiosis with the Central Nervous System Involvement.

PURPOSE: Anti-granulocyte-macrophage colony-stimulating factor autoantibodies (anti-GM-CSF Abs) are implicated in the pathogenesis of Cryptococcus gattii (C. gattii) infection and pulmonary alveolar proteinosis (PAP). Their presence has also been noted in nocardiosis cases, particularly those with disseminated disease. This study delineates a case series characterizing clinical features and specificity of anti-GM-CSF Abs in nocardiosis patients. METHODS: In this study, eight patients were recruited to determine the presence or absence of anti-GM-CSF Abs. In addition to the detailed description of the clinical course, we thoroughly investigated the autoantibodies regarding the characteristics, isotypes, subclasses, titers, and neutralizing capacities by utilizing the plasma samples from patients. RESULTS: Of eight patients, five tested positive for anti-GM-CSF Abs, all with central nervous system (CNS) involvement; patients negative for these antibodies did not develop CNS nocardiosis. Distinct from previously documented cases, none of our patients with anti-GM-CSF Abs exhibited PAP symptoms. The titer and neutralizing activity of anti-GM-CSF Abs in our cohort did not significantly deviate from those found in C. gattii cryptococcosis and PAP patients. Uniquely, one individual (Patient 3) showed a minimal titer and neutralizing action of anti-GM-CSF Abs, with no relation to disease severity. Moreover, IgM autoantibodies were notably present in all CNS nocardiosis cases investigated. CONCLUSION: The presence of anti-GM-CSF Abs suggests an intrinsic immunodeficiency predisposing individuals toward CNS nocardiosis. The presence of anti-GM-CSF Abs helps to elucidate vulnerability to CNS nocardiosis, even with low titer of autoantibodies. Consequently, systematic screening for anti-GM-CSF Abs should be considered a crucial diagnostic step for nocardiosis patients.

Clinical application and evaluation of metagenomic next-generation sequencing in pathogen detection for suspected central nervous system infections.

Central nervous system Infections (CNSIs) is a disease characterized by complex pathogens, rapid disease progression, high mortality rate and high disability rate. Here, we evaluated the clinical value of metagenomic next generation sequencing (mNGS) in the diagnosis of central nervous system infections and explored the factors affecting the results of mNGS. We conducted a retrospective study to compare mNGS with conventional methods including culture, smear and etc. 111 suspected CNS infectious patients were enrolled in this study, and clinical data were recorded. Chi-square test were used to evaluate independent binomial variables, taking p < 0.05 as statistically significant threshold. Of the 111 enrolled cases, 57.7% (64/111) were diagnosed with central nervous system infections. From these cases, mNGS identified 39.6% (44/111) true-positive cases, 7.2% (8/111) false-positive case, 35.1% (39/111) true-negative cases, and 18.0% (20/111) false-negative cases. The sensitivity and specificity of mNGS were 68.7% (44/64) and 82.9% (39/47), respectively. Compared with culture, mNGS provided a higher pathogen detection rate in CNSIs patients (68.7% (44/64) vs. 26.5% (17/64), p < 0.0001). Compared to conventional methods, positive percent agreement and negative percent agreement was 84.60% (44/52) and 66.1% (39/59) separately. At a species-specific read number (SSRN) ≥ 2, mNGS performance in the diagnosis of definite viral encephalitis and/or meningitis was optimal (area under the curve [AUC] 0.758, 95% confidence interval [CI] 0.663-0.854). In bacterial CNSIs patients with significant CSF abnormalities (CSF WBC > 300*106/L), the positive rate of CSF mNGS is higher. To sum up, conventional microbiologic testing is insufficient to detect all neuroinvasive pathogens, and mNGS exhibited satisfactory diagnostic performance in CNSIs and with an overall detection rate higher than culture (p < 0.0001).

Meropenem pharmacokinetics in cerebrospinal fluid: comparing intermittent and continuous infusion strategies in critically ill patients-a prospective cohort study.

Meropenem penetration into the cerebrospinal fluid (CSF) is subject to high interindividual variability resulting in uncertain target attainment in CSF. Recently, several authors recommended administering meropenem as a continuous infusion (CI) to optimize CSF exposure. This study aimed to compare the concentrations and pharmacokinetics of meropenem in CSF after intermittent infusion (II) and CI. This prospective, observational study (NCT04426383) included critically ill patients with external ventricular drains who received either II or CI of meropenem. Meropenem pharmacokinetics in plasma and CSF were characterized using population pharmacokinetic modeling (NONMEM 7.5). The developed model was used to compare the concentration-time profile and probability of target attainment (PTA) between II and CI. A total of 16 patients (8 CI, 8 II; samples: nplasma = 243, nCSF = 263) were recruited, with nine patients (5 CI, 4 II) suffering from cerebral and seven patients from extracerebral infections. A one-compartment model described the plasma concentrations adequately. Meropenem penetration into the CSF (partition coefficient (KP), cCSF/cplasma) was generally low (6.0%), exhibiting substantial between-subject variability (coefficient of variation: 84.0%). There was no correlation between the infusion mode and KP, but interleukin (IL)-6 measured in CSF showed a strong positive correlation with KP (P < 0.001). Dosing simulations revealed no relevant differences in CSF concentrations and PTA in CSF between CI and II. Our study did not demonstrate increased penetration rates or higher concentrations of meropenem in the CSF with CI compared with II. CLINICAL TRIALS: This study is registered with ClinicalTrials.gov as NCT04426383.

A Case of Klebsiella pneumoniae infection.

INTRODUCTION: In recent years, hypervirulent Klebsiella pneumoniae (hvKp) has attracted increasing attention. It usually causes liver abscesses, which spread through the bloodstream to other parts such as the eyes, brain, lungs. 5.5% of all paroxysmal sympathetic hyperactivity syndrome are associated with infection, hydrocephalus, brain tumors, and some unknown causes. Younger patients with focal lesions of the brain parenchyma are at higher risk of paroxysmal sympathetic hyperactivity (PSH). CASE PRESENTATION: This case report details the clinical features of Klebsiella pneumoniae diagnosed in a healthy individual. In addition to liver abscesses, bacteremia, and hyperglycemia, there are also brain abscesses, hernias, and postoperative paroxysmal sympathetic hyperactivity, an unexpected association between diseases or symptoms. The patient stabilized after comprehensive treatment, including early drainage of abscesses, rapid pathogen diagnosis, and timely and appropriate antibiotics. At a two-month follow-up, no signs of infection recurrence were noted, and the patient regained neurological function and could participate in regular physical activity. DISCUSSION: Symptoms of Klebsiella pneumoniae infection usually appear gradually, and misdiagnosis is common. When young patients suddenly develop high fever and abscess at a particular site, Klebsiella pneumoniae infection should be considered routine. Paroxysmal sympathetic hyperactivity syndrome caused by infection is rare, but a clinical score (PSH assessment measure, PSH-AM score) should be performed when clinical features appear. Early diagnosis and treatment can improve the prognosis.

Nocardia Infection in Patients With Anti-Granulocyte-Macrophage Colony-Stimulating Factor Autoantibodies: A Prospective Multicenter French Study.

Background: Nocardiosis, a bacterial opportunistic infection caused by Nocardia spp, has recently been reported in patients with anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies, but insufficient data are available about disease presentation, outcomes, and occurrence of autoimmune pulmonary alveolar proteinosis (aPAP) in this population. Methods: We performed a prospective, multicenter, nationwide study in France and included patients with a Nocardia infection who had anti-GM-CSF autoantibodies. We describe their clinical, microbiological, and radiological characteristics, and their outcome at 1 year of follow-up. Results: Twenty patients (18 [90%] male) were included, with a median age of 69 (interquartile range, 44-75) years. The organs most frequently involved were the brain (14/20 [70%]) and the lung (12/20 [60%]). Half of the infections were disseminated (10/20 [50%]). Nocardia identification was predominantly made in abscess fluid (17/20 [85%]), among which 10 (59%) were brain abscesses. The 1-year all-cause mortality was 5% (1/20), and only 1 case of aPAP (1/20 [5%]) occurred during the follow-up period. Conclusions: Nocardiosis with anti-GM-CSF autoantibodies is associated with a low mortality rate despite a high incidence of brain involvement. Although the occurrence of aPAP was infrequent during the 1-year follow-up period, long-term clinical data are needed to fully understand the potential relationship between nocardiosis, anti-GM-CSF autoantibodies, and aPAP.

C1q is elevated during chronic Staphylococcus epidermidis central nervous system catheter infection.

Introduction: Significant neurologic morbidity is caused by pediatric cerebrospinal fluid (CSF) shunt infections. The underlying mechanisms leading to impaired school performance and increased risk of seizures are unknown, however, a better understanding of these mechanisms may allow us to temper their consequences. Recent evidence has demonstrated important roles for complement proteins in neurodevelopment and neuroinflammation. Methods: We examined complement activation throughout Staphylococcus epidermidis (S. epidermidis) central nervous system (CNS) catheter infection. In addition, based on accumulating evidence that C3 plays a role in synaptic pruning in other neuroinflammatory states we determined if C3 and downstream C5 led to alterations in synaptic protein levels. Using our murine model of S. epidermidis catheter infection we quantified levels of the complement components C1q, Factor B, MASP2, C3, and C5 over the course of infection along with bacterial burdens. Results: We found that MASP2 predominated early in catheter infection, but that Factor B was elevated at intermediate time points. Unexpectedly C1q was elevated at late timepoints when bacterial burdens were low or undetectable. Based on these findings and the wealth of information regarding the emerging roles of C1q in the CNS, this suggests functions beyond pathogen elimination during S. epidermidis CNS catheter infection. To identify if C3 impacted synaptic protein levels we performed synaptosome isolation and quantified levels of VGLUT1 and PSD95 as well as pre-, post- and total synaptic puncta in cortical layer V of C3 knockout (KO) and wild type mice. We also used C5 KO and wild type mice to determine if there was any difference in pre-, post- and total synaptic puncta. Discussion: Neither C3 nor C5 impacted synaptic protein abundance. These findings suggest that chronic elevations in C1q in the brain that persist once CNS catheter infection has resolved may be modulating disease sequalae.

Intracranial infection caused by Mycobacterium rhodesiae with specific imaging findings and good response to medication: a case report and literature review.

Nontuberculous mycobacteria (NTM) are exceedingly rare etiological agents of intracranial infections. Among them, Mycobacterium rhodesiae stands out as an even less common pathogen. In this paper, we report the first documented case of a central nervous system (CNS) infection in humans caused by Mycobacterium rhodesiae, which has specific imaging findings and good response to the therapy by using Linezolid, Clarithromycin, and Minocycline. The diagnosis was facilitated by a comprehensive multimodal approach, incorporating multisite imaging, cerebrospinal fluid analysis via next-generation sequencing (NGS), and targeted genetic testing. Furthermore, this paper provides a derivation of the clinical characteristics observed in other documented instances of CNS infections attributable to NTM and based on a review of the current literature. Our experience contributes to the evidence that is needed to understand the full spectrum of NTM-related CNS pathologies and underscores the importance of a multidisciplinary diagnostic process in atypical presentations of intracranial infections.

[Concerns of Performance Evaluation on Central Nervous System Infection Pathogen Metagenome Sequencing Reagent].

From the perspective of the performance evaluation, concerns of the range of pathogens, establishment of enterprise reference material, reaction system study and analytical performances evaluation of central nervous system infection pathogen metagenome sequencing reagent are briefly described, including study methods and quality control requirements. This study is intended to increase the research and development efficiency of products, and contribute to the development of associated industry.

Biomarkers and genotypes in patients with Central nervous system infection caused by enterovirus.

PURPOSE: Enteroviruses (EV) comprises many different types and are the most common cause of aseptic meningitis. How the virus affects the brain including potential differences between types are largely unknown. Measuring biomarkers in CSF is a tool to estimate brain damage caused by CNS infections. METHODS: A retrospective study was performed in samples from 38 patients with acute neurological manifestations and positive CSF-EV RNA (n = 37) or serum-IgM (n = 1). The EV in 17 samples were typed by sequencing. The biomarkers neurofilament light (NFL), glial fibrillary acidic protein (GFAP), S-100B protein, amyloid-ß (Aß) 40 and Aß42, total-tau (T-tau) and phosphorylated tau (P-tau) were measured and compared with data derived from a control group (n = 19). RESULTS: There were no increased levels of GFAP (p ≤ 0.1) nor NFL (p ≤ 0.1) in the CSF of patients with EV meningitis (n = 38) compared with controls. However, we found decreased levels of Aß42 (p < 0.001), Aß40 (p < 0.001), T-tau (p ≥ 0.01), P-tau (p ≤ 0.001) and S-100B (p ≤ 0.001). E30 (n = 9) and CVB5 (n = 6) were the most frequent EV-types identified, but no differences in biomarker levels or other clinical parameters were found between the infecting virus type. Seven patients who were followed for longer than one month reported remaining cognitive impairment, although no correlations with biomarker concentrations were observed. CONCLUSION: There are no indication of neuronal or astrocyte damage in patients with EV meningitis. Yet, decreased concentrations of Aß40, Aß42, P-tau and T-tau were shown, a finding of unknown importance. Cognitive impairment after acute disease occurs, but with only a limited number of patients analysed, no conclusion can be drawn concerning any association with biomarker levels or EV types.

Cerebral Infectious Opportunistic Lesions in a Patient with Acute Myeloid Leukaemia: The Challenge of Diagnosis and Clinical Management.

Central nervous system (CNS) lesions, especially invasive fungal diseases (IFDs), in immunocompromised patients pose a great challenge in diagnosis and treatment. We report the case of a 48-year-old man with acute myeloid leukaemia and probable pulmonary aspergillosis, who developed hyposthenia of the left upper limb, after achieving leukaemia remission and while on voriconazole. Magnetic resonance imaging (MRI) showed oedematous CNS lesions with a haemorrhagic component in the right hemisphere with lepto-meningitis. After 2 weeks of antibiotics and amphotericin-B, brain biopsy revealed chronic inflammation with abscess and necrosis, while cultures were negative. Clinical recovery was attained, he was discharged on isavuconazole and allogeneic transplant was postponed, introducing azacitidine as a maintenance therapy. After initial improvement, MRI worsened; brain biopsy was repeated, showing similar histology; and 16S metagenomics sequencing analysis was positive (Veilonella, Pseudomonas). Despite 1 month of meropenem, MRI did not improve. The computer tomography and PET scan excluded extra-cranial infectious-inflammatory sites, and auto-immune genesis (sarcoidosis, histiocytosis, CNS vasculitis) was deemed unlikely due to the histological findings and unilateral lesions. We hypothesised possible IFD with peri-lesion inflammation and methyl-prednisolone was successfully introduced. Steroid tapering is ongoing and isavuconazole discontinuation is planned with close follow-up. In conclusion, the management of CNS complications in immunocompromised patients needs an interdisciplinary approach.

A Difficult Case of Ventriculitis in a 40-Year-Old Woman with Acute Myeloid Leukemia.

Ventriculitis and nosocomial meningitis caused by carbapenem-resistant Gram-negative and vancomycin-resistant Gram-positive bacteria represent a growing treatment challenge. A case of ventriculitis and bacteremia caused by carbapenem-resistant, KPC-producing Klebsiella pneumoniae and vancomycin-resistant Enterococcus faecium in a young woman with acute leukemia who was successfully treated with meropenem/vaborbactam (MVB), rifampicin, and linezolid is described in this paper. This case report emphasizes the importance of a multidisciplinary strategy, including infectious focus control, for the treatment of device-associated central nervous system (CNS) infections from multidrug-resistant bacteria. Considering the novel resistance patterns, more research on drug penetration into the central nervous system, as well as on the necessity of association therapies, is needed.

Bicyclic Pyrrolidine Inhibitors of Toxoplasma gondii Phenylalanine t-RNA Synthetase with Antiparasitic Potency In Vitro and Brain Exposure.

Previous studies have shown that bicyclic azetidines are potent and selective inhibitors of apicomplexan phenylalanine tRNA synthetase (PheRS), leading to parasite growth inhibition in vitro and in vivo, including in models of Toxoplasma infection. Despite these useful properties, additional optimization is required for the development of efficacious treatments of toxoplasmosis from this inhibitor series, in particular, to achieve optimal exposure in the brain. Here, we describe a series of PheRS inhibitors built on a new bicyclic pyrrolidine core scaffold designed to retain the exit-vector geometry of the isomeric bicyclic azetidine core scaffold while offering avenues to sample diverse chemical space. Relative to the parent series, bicyclic pyrrolidines retain reasonable potency and target selectivity for parasite PheRS vs host. Further structure-activity relationship studies revealed that the introduction of aliphatic groups improved potency and ADME and PK properties, including brain exposure. The identification of this new scaffold provides potential opportunities to extend the analogue series to further improve selectivity and potency and ultimately deliver a novel, efficacious treatment of toxoplasmosis.

Meropenem-Vaborbactam for the Treatment of Post-Neurosurgical Meningitis Caused by KPC Producer Klebsiella Pneumoniae: A Case Report and Review of the Literature.

Meningitis and ventriculitis, due to carbapenem-resistant Enterobacterales, are frequently associated with significant morbidity and mortality. In the case of multi-drug-resistant pathogens, it is necessary to consider the limited susceptibility profile as well as the penetration of the antimicrobials into the brain. Limited data are available regarding the treatment of central nervous system infections caused by carbapenem-resistant Enterobacterales. We report a study of a patient treated with meropenem-vaborbactam in the case of post-neurosurgical meningitis due to carbapenemase-producing Klebsiella pneumoniae (CPKP).

The application value of metagenomic next-generation sequencing technology in the diagnosis and treatment of neonatal infectious meningitis - a single center retrospective case-control study.

OBJECTIVE: This retrospective study was conducted to investigate the application value of metagenomics next generation sequencing (mNGS) technology in the diagnosis and treatment of neonatal infectious meningitis. METHODS: From 1 January 2020 to 31 December 2022, 73 newborns suspected of infectious meningitis were hospitalized. After screening by inclusion and exclusion criteria, 69 newborns were subsequently included in the study, containing 27 cases with positive mNGS result and 42 cases with negative mNGS result. Furthermore, according to the diagnosis of meningitis, mNGS positive group and mNGS negative group were further divided into infectious meningitis with mNGS (+) group (n = 27) and infectious meningitis with mNGS (-) group (n = 26), respectively. RESULTS: (1) Compared with cerebrospinal fluid (CSF) culture, mNGS has better diagnostic value [positive predictive value (PPV) = 100.00% (27/27), negative predictive value (NPV) = 38.10% (16/42), agreement rate = 62.32% (43/69), area under the curve (AUC) = 0.750, 95% confidence interval (CI): 0.636-0.864]. (2) There were significant differences in the onset age, age at first CSF test, CSF leukocyte count, CSF glucose, positive rate of CSF culture, blood leukocyte count, procalcitonin (PCT), C-reaction protein (CRP), age at first mNGS test and adjusting anti-infective medication in the comparison between infectious meningitis with mNGS (+) group and infectious meningitis with mNGS (-) group (p < 0.05). (3) mNGS could help improve the cure rate [crude odds ratio (OR) = 3.393, 95%CI: 1.072-10.737; adjusted OR = 15.580, 95%CI: 2.114-114.798]. CONCLUSION: Compared with classic meningitis detection methods, mNGS has better PPV, NPV, agreement rate, and AUC. mNGS could help improve the cure rate.

Neurological Spectrum of Epstein-Barr Virus Infection: A Rare Clinical Case.

The Epstein-Barr virus (EBV) is a DNA virus that has been infecting humans since ancient times, capable of causing a wide range of pathologies and affecting approximately 90% of the population. A 61-year-old male with no significant medical history presented with a 5-day history of imbalance and difficulty walking. Neurological examination revealed specific findings, including absent reflexes, bilateral asynergy, and gait abnormalities. Contrasting with Guillain-Barré Syndrome, lumbar puncture suggested a central nervous system infection. Serological testing confirmed Epstein-Barr virus (EBV) positivity, and intravenous immunoglobulin led to significant improvement. Electromyogram results suggested inflammatory/ipnfectious polyradiculopathy. Repeat EBV serology, showing strongly positive IgG and negative IgM, confirmed the diagnosis of Polyradiculoneuropathy secondary to EBV. This case underscores the rare neurological complications of EBV and the importance of considering viral infections in such presentations.

Bicyclic pyrrolidine inhibitors of Toxoplasma gondii phenylalanine t-RNA synthetase with antiparasitic potency in vitro and brain exposure.

Previous studies have shown that bicyclic azetidines are potent and selective inhibitors of apicomplexan phenylalanine tRNA synthetase (PheRS), leading to parasite growth inhibition in vitro and in vivo, including in models of Toxoplasma infection. Despite these useful properties, additional optimization is required for the development of efficacious treatments of toxoplasmosis from this inhibitor series, in particular to achieve sufficient exposure in the brain. Here, we describe a series of PheRS inhibitors built on a new bicyclic pyrrolidine core scaffold designed to retain the exit-vector geometry of the isomeric bicyclic azetidine core scaffold while offering avenues to sample diverse chemical space. Relative to the parent series, bicyclic pyrrolidines retain reasonable potency and target selectivity for parasite PheRS vs. host. Further structure-activity relationship studies revealed that the introduction of aliphatic groups improved potency, ADME and PK properties, including brain exposure. The identification of this new scaffold provides potential opportunities to extend the analog series to further improve selectivity and potency and ultimately deliver a novel, efficacious treatment of toxoplasmosis.

Pathophysiology of chikungunya virus infection associated with fatal outcomes.

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes acute, subacute, and chronic human arthritogenic diseases and, in rare instances, can lead to neurological complications and death. Here, we combined epidemiological, virological, histopathological, cytokine, molecular dynamics, metabolomic, proteomic, and genomic analyses to investigate viral and host factors that contribute to chikungunya-associated (CHIK) death. Our results indicate that CHIK deaths are associated with multi-organ infection, central nervous system damage, and elevated serum levels of pro-inflammatory cytokines and chemokines compared with survivors. The histopathologic, metabolite, and proteomic signatures of CHIK deaths reveal hemodynamic disorders and dysregulated immune responses. The CHIKV East-Central-South-African lineage infecting our study population causes both fatal and survival cases. Additionally, CHIKV infection impairs the integrity of the blood-brain barrier, as evidenced by an increase in permeability and altered tight junction protein expression. Overall, our findings improve the understanding of CHIK pathophysiology and the causes of fatal infections.

Intraventricular or intrathecal polymyxin B for treatment of post-neurosurgical intracranial infection caused by carbapenem-resistant gram-negative bacteria: a 8-year retrospective study.

PURPOSE: Post-neurosurgical intracranial infection caused by carbapenem-resistant gram-negative bacteria (CRGNB) is a life-threatening complication. This study aimed to assess the current practices and clinical outcomes of intravenous (IV) combined with intraventricular (IVT)/intrathecal (ITH) polymyxin B in treating CRGNB intracranial infection. METHODS: A retrospective study was conducted on patients with post-neurosurgical intracranial infection due to CRGNB from January 2013 to December 2020. Clinical characteristics and treatment outcomes were collected and described. Kaplan-Meier survival and multivariate logistic regression analyses were performed. RESULTS: The study included 114 patients, of which 72 received systemic antimicrobial therapy combined with IVT/ITH polymyxin B, and 42 received IV administration alone. Most infections were caused by carbapenem-resistant Acinetobacter baumannii (CRAB, 63.2%), followed by carbapenem-resistant Klebsiella pneumoniae (CRKP, 31.6%). Compared with the IV group, the IVT/ITH group had a higher cerebrospinal fluid (CSF) sterilization rate in 7 days (p < 0.001) and lower 30-day mortality (p = 0.032). In the IVT/ITH group, patients with CRKP infection had a higher initial fever (p = 0.014), higher incidence of bloodstream infection (p = 0.040), lower CSF sterilization in 7 days (p < 0.001), and higher 30-day mortality (p = 0.005) than those with CRAB infection. Multivariate logistic regression analysis revealed that the duration of IVT/ITH polymyxin B (p = 0.021) was independently associated with 30-day mortality. CONCLUSIONS: Intravenous combined with IVT/ITH polymyxin B increased CSF microbiological eradication and improved clinical outcomes. CRKP intracranial infections may lead to more difficult treatment and thus warrant attention and further optimized treatment.

Granulocytes in cerebrospinal fluid of adults suspected of a central nervous system infection: a prospective study of diagnostic accuracy.

PURPOSE: Cerebrospinal fluid (CSF) granulocytes are associated with bacterial meningitis, but information on its diagnostic value is limited and primarily based on retrospective studies. Therefore, we assessed the diagnostic accuracy of CSF granulocytes. METHODS: We analyzed CSF granulocytes (index test) from all consecutive patients in two prospective cohort studies in the Netherlands. Both studies included patients ≥ 16 years, suspected of a central nervous system (CNS) infection, who underwent a diagnostic lumbar puncture. All episodes with elevated CSF leukocytes (≥ 5 cells per mm3) were selected and categorized by clinical diagnosis (reference standard). RESULTS: Of 1261 episodes, 625 (50%) had elevated CSF leukocytes and 541 (87%) were included. 117 of 541 (22%) were diagnosed with bacterial meningitis, 144 (27%) with viral meningoencephalitis, 49 (9%) with other CNS infections, 76 (14%) with CNS autoimmune disorders, 93 (17%) with other neurological diseases and 62 (11%) with systemic diseases. The area under the curve to discriminate bacterial meningitis from other diagnoses was 0.97 (95% confidence interval [CI] 0.95-0.98) for CSF granulocyte count and 0.93 (95% CI 0.91-0.96) for CSF granulocyte percentage. CSF granulocyte predominance occurred in all diagnostic categories. A cutoff at 50% CSF granulocytes gave a sensitivity of 94% (95% CI 90-98), specificity of 80% (95% CI 76-84), negative predictive value of 98% (95% CI 97-99) and positive predictive value of 57% (95% CI 52-62). CONCLUSION: CSF granulocytes have a high diagnostic accuracy for bacterial meningitis in patients suspected of a CNS infection. CSF granulocyte predominance occurred in all diagnostic categories, limiting its value in clinical practice.

NK cell profiling in West Nile virus encephalitis reveals potential metabolic basis for functional inhibition.

Natural killer (NK) cells are cytotoxic lymphocytes important for viral defense. West Nile virus (WNV) infection of the central nervous system (CNS) causes marked recruitment of bone marrow (BM)-derived monocytes, T cells and NK cells, resulting in severe neuroinflammation and brain damage. Despite substantial numbers of NK cells in the CNS, their function and phenotype remain largely unexplored. Here, we demonstrate that NK cells mature from the BM to the brain, upregulate inhibitory receptors and show reduced cytokine production and degranulation, likely due to the increased expression of the inhibitory NK cell molecule, MHC-I. Intriguingly, this correlated with a reduction in metabolism associated with cytotoxicity in brain-infiltrating NK cells. Importantly, the degranulation and killing capability were restored in NK cells isolated from WNV-infected tissue, suggesting that WNV-induced NK cell inhibition occurs in the CNS. Overall, this work identifies a potential link between MHC-I inhibition of NK cells and metabolic reduction of their cytotoxicity during infection.