PCR-positive meningococcal CSF infection without pleocytosis but high IL-6 and IL-8.

BACKGROUND: Meningococcal meningitis is still a severe disease causing high mortality and morbidity rates. Early diagnosis is crucial to ensure prompt antibiotic therapy. However, identification of the pathogen can be challenging. CASE PRESENTATION: A 32-year-old male patient with systemic lupus erythematosus (SLE) presented to the emergency room with fever, nausea, vomiting, headache and lower back pain as well as multiple petechial bleedings. On suspicion of meningococcal infection, the emergency doctor had already administered one dose of ceftriaxone before arrival to the clinic. Blood works showed massive inflammation due to bacterial infection. Cerebrospinal fluid (CSF) analysis showed normal cell count, protein and glucose levels but PCR was positive for Neisseria meningitis and IL-6 as well as IL-8 were elevated. On antibiotic therapy with ceftriaxone, the patient's condition improved quickly. CONCLUSIONS: We present a rare case of meningococcal infection of the CSF in a SLE patient without further CSF abnormalities. We discuss the involvement of early antibiotic treatment and the role of the patient's immune status in the normal CSF findings of this case. Moreover, this case demonstrates the importance of early antibiotic therapy in bacterial meningitis for the clinical outcome.

Characterization and diagnosis spectrum of patients with cerebrospinal fluid pleocytosis.

PURPOSE: There is an overlap in the cerebrospinal fluid (CSF) characteristics of patients presenting with different etiologies of CSF pleocytosis. Here, we characterized patients with CSF pleocytosis treated in a large hospital. METHODS: A retrospective cohort study of 1150 patients with an elevated CSF leukocyte count > 5 cells/µl treated at a university hospital in Germany from January 2015 to December 2017 was performed. Information on clinical presentation, laboratory parameters, diagnosis and outcome was collected. Clinical and laboratory features were tested for their potential to differentiate between bacterial meningitis (BM) and other causes of CSF pleocytosis. RESULTS: The most common etiologies of CSF pleocytosis were CNS infections (34%: 20% with detected pathogen, 14% without), autoimmune (21%) and neoplastic diseases (16%). CSF cell count was higher in CNS infections with detected pathogen (median 82 cells/µl) compared to autoimmune (11 cells/µl, p = 0.001), neoplastic diseases (19 cells/µl, p = 0.01) and other causes (11 cells/µl, p < 0.001). The CHANCE score was developed to differentiate BM from other causes of CSF pleocytosis: Multivariate regression revealed that CSF cell count > 100 cells/µl, CSF protein > 100 mg/dl, CRP > 5 mg/dl, elevated white blood cell count, abnormal mental status and nuchal rigidity are important indicators. The CHANCE score identified patients with BM with high sensitivity (92.1%) and specificity (90.9%) (derivation cohort: AUC: 0.955, validation cohort: AUC: 0.956). CONCLUSION: Overall, the most common causes for CSF pleocytosis include infectious, neoplastic or autoimmune CNS diseases in ~ 70% of patients. The CHANCE score could be of help to identify patients with high likelihood of BM and support clinical decision making.

Pericytes are protective in experimental pneumococcal meningitis through regulating leukocyte infiltration and blood-brain barrier function.

BACKGROUND: Brain pericytes participate in the regulation of cerebral blood flow and the maintenance of blood-brain barrier integrity. Because of their perivascular localization, their receptor repertoire, and their potential ability to respond to inflammatory and infectious stimuli by producing various cytokines and chemokines, these cells are also thought to play an active role in the immune response to brain infections. This assumption is mainly supported by in vitro studies, investigations in in vivo disease models are largely missing. Here, we analysed the role of brain pericytes in pneumococcal meningitis, in vitro and in vivo in two animal models of pneumococcal meningitis. METHODS: Primary murine and human pericytes were stimulated with increasing concentrations of different serotypes of Streptococcus pneumoniae in the presence or absence of Toll-like receptor inhibitors and their cell viability and cytokine production were monitored. To gain insight into the role of pericytes in brain infection in vivo, we performed studies in a zebrafish embryo model of pneumococcal meningitis in which pericytes were pharmacologically depleted. Furthermore, we analyzed the impact of genetically induced pericyte ablation on disease progression, intracranial complications, and brain inflammation in an adult mouse model of this disease. RESULTS: Both murine and human pericytes reacted to pneumococcal exposure with the release of selected cytokines. This cytokine release is pneumolysin-dependent, TLR-dependent in murine (but not human) pericytes and can be significantly increased by macrophage-derived IL-1b. Pharmacological depletion of pericytes in zebrafish embryos resulted in increased cerebral edema and mortality due to pneumococcal meningitis. Correspondingly, in an adult mouse meningitis model, a more pronounced blood-brain barrier disruption and leukocyte infiltration, resulting in an unfavorable disease course, was observed following genetic pericyte ablation. The degree of leukocyte infiltration positively correlated with an upregulation of chemokine expression in the brains of pericyte-depleted mice. CONCLUSIONS: Our findings show that pericytes play a protective role in pneumococcal meningitis by impeding leukocyte migration and preventing blood-brain barrier breaching. Thus, preserving the integrity of the pericyte population has the potential as a new therapeutic strategy in pneumococcal meningitis.

Cerebrospinal fluid analysis in emergency patients with suspected infection of the central nervous system.

BACKGROUND AND PURPOSE: Meningitis and encephalitis are potentially life-threatening diseases that require fast and accurate diagnostics and therapy. The value of polymerase chain reaction (PCR) multiplex testing in clinical practice is still a matter of debate. This study aims to evaluate its benefits and limitations in emergency patients. METHODS: We assessed the value of a meningoencephalitis PCR array in the clinical routine of an emergency department. RESULTS: Of 1578 emergency patients who received a lumbar puncture, 43% received it for a clinically suspected central nervous system (CNS) infection. After initial workup for cerebrospinal fluid (CSF) cell count, protein and glucose, a CNS infection was still considered likely in 307 patients. In these patients, further microbiologic workup was performed. A total of 230 samples were examined by PCR and a pathogen was detected in 66 of these samples. In the case of a positive microbiologic result, a comparison between PCR array and standard method was available for 59 samples, which demonstrated an overcall agreement of 80% (n = 47/59). Of interest, exclusively array-positive results were observed for patients with meningitis found to be positive for Streptococcus pneumoniae; four out of five patients had been treated with antibiotics before the lumbar puncture. In samples with normal CSF cell count only two positive array results were obtained, both for human herpesvirus 6, and these were not clinically relevant. CONCLUSION: Our data suggest that the array substantially contributes to a detection of pathogens in patients with suspected CNS infection and seems of particular interest in patients with acute bacterial meningitis under empiric antibiotic treatment. In CSF samples with normal cell count, it might be dispensable.

Quantitative proteomic analysis of cerebrospinal fluid from patients with idiopathic facial nerve palsy.

BACKGROUND AND PURPOSE: Idiopathic facial palsy (IFP) accounts for over 60% of peripheral facial palsy (FP) cases. The cause of IFP remains to be determined. Possible etiologies are nerve swelling due to inflammation and/or viral infection. In this study, we applied an integrative mass spectrometry approach to identify possibly altered protein patterns in the cerebrospinal fluid (CSF) of IFP patients. METHODS: We obtained CSF samples from 34 patients with FP. In four patients, varicella-zoster virus was the cause (VZV-FP). Among the 30 patients diagnosed with IFP, 17 had normal CSF parameters, five had slightly elevated CSF cell counts and normal or elevated CSF protein, and eight had normal CSF cell counts but elevated CSF protein. Five patients with primary headache served as controls. All samples were tested for viral pathogens by PCR and subjected to liquid chromatography tandem mass spectrometry and bioinformatics analysis and multiplex cytokine/chemokine arrays. RESULTS: All CSF samples, except those from VZV-FP patients, were negative for all tested pathogens. The protein composition of CSF samples from IFP patients with normal CSF was comparable to controls. IFP patients with elevated CSF protein showed dysregulated proteins involved in inflammatory pathways, findings which were similar to those in VZV-FP patients. Multiplex analysis revealed similarly elevated cytokine levels in the CSF of IFP patients with elevated CSF protein and VZV-FP. CONCLUSIONS: Our study revealed a subgroup of IFP patients with elevated CSF protein that showed upregulated inflammatory pathways, suggesting an inflammatory/infectious cause. However, no evidence for an inflammatory cause was found in IFP patients with normal CSF.

[Influence of the COVID-19 pandemic on the occurrence of neurological infectious diseases]. / Einfluss der COVID-19-Pandemie auf das Auftreten neuroinfektiologischer Erkrankungen.

BACKGROUND: During the coronavirus disease 2019 (COVID-19) pandemic a wide range of hygiene measures were implemented to contain the spread of infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Besides a mitigation of SARS-CoV­2, a decline in the number of other respiratory tract infections could be observed. Interestingly, the numbers for some infections of the central nervous system (CNS) decreased as well. OBJECTIVE: This review article shows the development of important CNS infections in Germany during the COVID-19 pandemic. MATERIAL AND METHOD: This article is based on relevant literature on the epidemiology of CNS infections during the COVID-19 pandemic up to autumn 2022. RESULTS: During the COVID-19 pandemic the frequency of bacterial meningitis caused by Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae significantly declined. The frequency of viral meningitis, particularly those caused by Enterovirus, decreased as well. In contrast, the number of patients suffering from tick-borne encephalitis significantly increased within the first year of the pandemic. DISCUSSION: During the pandemic there was a decrease in cases of bacterial and viral meningitis, most likely due to the general containment strategies and social contact restrictions. The increase of infections transmitted by ticks could be a consequence of changed leisure activities during the pandemic.

Travel-associated neurological disease terminated in a postmortem diagnosed atypical HSV-1 encephalitis after high-dose steroid therapy - a case report.

BACKGROUND: Human encephalitis can originate from a variety of different aetiologies, of which infection is the most common one. The diagnostic work-up is specifically challenging in patients with travel history since a broader spectrum of unfamiliar additional infectious agents, e. g. tropical disease pathogens, needs to be considered. Here we present a case of encephalitis of unclear aetiology in a female traveller returning from Africa, who in addition developed an atypical herpes simplex virus (HSV) encephalitis in close temporal relation with high-dose steroid treatment. CASE PRESENTATION: A previously healthy 48-year-old female presented with confusion syndrome and impaired vigilance which had developed during a six-day trip to The Gambia. The condition rapidly worsened to a comatose state. Extensive search for infectious agents including a variety of tropical disease pathogens was unsuccessful. As encephalitic signs persisted despite of calculated antimicrobial and antiviral therapy, high-dose corticosteroids were applied intravenously based on the working diagnosis of an autoimmune encephalitis. The treatment did, however, not improve the patient's condition. Four days later, bihemispheric signal amplification in the insular and frontobasal cortex was observed on magnetic resonance imaging (MRI). The intracranial pressure rapidly increased and could not be controlled by conservative treatment. The patient died due to tonsillar herniation 21 days after onset of symptoms. Histological examination of postmortem brain tissue demonstrated a generalized lymphocytic meningoencephalitis. Immunohistochemical reactions against HSV-1/2 indicated an atypical manifestation of herpesviral encephalitis in brain tissue. Moreover, HSV-1 DNA was detected by a next-generation sequencing (NGS) metagenomics approach. Retrospective analysis of cerebrospinal fluid (CSF) and serum samples revealed HSV-1 DNA only in specimens one day ante mortem. CONCLUSIONS: This case shows that standard high-dose steroid therapy can contribute to or possibly even trigger fulminant cerebral HSV reactivation in a critically ill patient. Thus, even if extensive laboratory diagnostics including wide-ranging search for infectious pathogens has been performed before and remained without results, continuous re-evaluation of potential differential diagnoses especially regarding opportunistic infections or reactivation of latent infections is of utmost importance, particularly if new symptoms occur.

Challenges in HSV encephalitis: normocellular CSF, unremarkable CCT, and atypical MRI findings.

PURPOSE: Herpes simplex virus (HSV) encephalitis continues to be the most common form of sporadic lethal encephalitis worldwide. The wide spectrum of clinical presentations and laboratory findings often poses a diagnostic challenge for physicians which might delay administration of life-saving therapy with acyclovir. Atypical presentations of HSV encephalitis have become increasingly prevalent with better diagnostic techniques and have not been well studied. METHODS: We retrospectively evaluated all consecutive PCR-proven HSV encephalitis cases treated at the Hospital of the Ludwig-Maximilians-University in Munich, Germany from January 1, 2013 to February 28, 2018. RESULTS: We included 18 patients with PCR-proven HSV encephalitis. The most common clinical features were altered mental status (77.8%), focal neurologic deficits (72.2%) and fever (72.2%). Remarkably, four of these patients (22.2%) had a normocellular cerebrospinal fluid (CSF) on admission. Electroencephalography and magnetic resonance imaging abnormalities were highly sensitive for HSV encephalitis independent of CSF cell count. Striking atypical findings on MRI were extensive global brain swelling and severe brainstem involvement in single patients. Of note, initial CT scans were normal in 11 out of 16 patients (68.8%). All patients were treated with acyclovir. Three patients still developed a clinical deterioration under therapy with acyclovir with one patient requiring decompressive craniotomy due to bilateral space-occupying temporal lobe hemorrhage. 94.4% of the patients survived but only 38.9% were discharged with a good clinical outcome (Glasgow Outcome Score = 5). CONCLUSION: Atypical presentations of HSV encephalitis seem to be more common than previously thought and physicians should apply a high level of clinical suspicion and a low threshold to initiate life-saving acyclovir therapy in suspected cases.

Impaired Consciousness in the Emergency Department.

BACKGROUND: The approach to unconscious patients in the emergency department (ED) is difficult, often depends on local resources and interests, and workup strategies often lack standardization. One reason for this is that data on causes, management, and outcome of patients who present to the ED with sudden onset unconsciousness of unknown cause is limited. OBJECTIVES: This study was performed to analyze the causes of acute impaired consciousness in patients in an interdisciplinary ED. METHODS: Here, we analyzed all patients who were admitted to the ED of a tertiary care hospital with the dominating symptom of "sudden onset unconsciousness" within 1 year (September 2014 until August 2015). Patients with a clear diagnosis at arrival that explained the altered state of consciousness or other dominating symptoms at the time of arrival were not included. RESULTS: A total of 212 patients were analyzed. In 88% of the patients, a final diagnosis could be established in the ED. Most common causes for unconsciousness were cerebrovascular diseases (24%), infections (14%), epileptic seizures (12%), psychiatric diseases (8%), metabolic causes (7%), intoxications (7%), transient global amnesia (5%), and cardiovascular causes (4%). The diagnoses were predominantly established by physical examination in combination with computed tomography (23%) and by the results of laboratory testing (25%). In-hospital mortality was 11%, and 59% of all patients were discharged with a Glasgow Outcome Score of 2-4. CONCLUSIONS: This analysis demonstrates a large variety of etiologies in patients with unknown unconsciousness of acute onset who are admitted to an ED. As neurological diagnoses are among the most common etiologies, neurological qualification is required in the ED, and availability of diagnostics such as cerebral imaging is indispensable and recommended as an early step in a standardized clinical approach.

Lyme neuroborreliosis.

PURPOSE OF REVIEW: Lyme disease is a multistage and multisystem disease. Neurological manifestations [termed Lyme neuroborreliosis (LNB)] occur in about 10% of patients with Lyme disease. Diagnostics and treatment of early and late LNB are widely established. However, the management of persistent symptoms is still fraught with controversies, and therefore is the focus of this review. RECENT FINDINGS: The incidence of Lyme disease seems to be much higher than previously assumed. Laboratory methods (namely serological tests) are essential for diagnosing LNB, but only when performed according to the guidelines of scientific medical societies. Most patients treated for LNB have good outcomes. However, some patients remain with nonspecific symptoms despite conventional therapy, a syndrome called posttreatment Lyme disease syndrome (PTLDS). IDSA has provided a formal definition of PTLDS, but its pathogenesis and even its existence remains to be clarified. Of note, there is evidence that these patients do not suffer from persistent Borrelia burgdorferi infection and do not benefit from additional antibiotic therapy. SUMMARY: Acute and late LNB are well established disorders. The existence of PTLDS as a disease entity is still unclear and needs further investigation. Unorthodox alternative therapies advertised to patients with Lyme disease on the Internet are not proven to be effective and well tolerated.

The immunoregulator soluble TACI is released by ADAM10 and reflects B cell activation in autoimmunity.

BAFF and a proliferation-inducing ligand (APRIL), which control B cell homeostasis, are therapeutic targets in autoimmune diseases. TACI-Fc (atacicept), a soluble fusion protein containing the extracellular domain of the BAFF-APRIL receptor TACI, was applied in clinical trials. However, disease activity in multiple sclerosis unexpectedly increased, whereas in systemic lupus erythematosus, atacicept was beneficial. In this study, we show that an endogenous soluble TACI (sTACI) exists in vivo. TACI proteolysis involved shedding by a disintegrin and metalloproteinase 10 releasing sTACI from activated B cells. The membrane-bound stub was subsequently cleaved by γ-secretase reducing ligand-independent signaling of the remaining C-terminal fragment. The shed ectodomain assembled ligand independently in a homotypic way. It functioned as a decoy receptor inhibiting BAFF- and APRIL-mediated B cell survival and NF-κB activation. We determined sTACI levels in autoimmune diseases with established hyperactivation of the BAFF-APRIL system. sTACI levels were elevated both in the cerebrospinal fluid of the brain-restricted autoimmune disease multiple sclerosis correlating with intrathecal IgG production, as well as in the serum of the systemic autoimmune disease systemic lupus erythematosus correlating with disease activity. Together, we show that TACI is sequentially processed by a disintegrin and metalloproteinase 10 and γ-secretase. The released sTACI is an immunoregulator that shares decoy functions with atacicept. It reflects systemic and compartmentalized B cell accumulation and activation.

Reversible cerebral vasoconstriction syndrome and posterior reversible encephalopathy syndrome associated with intracranial hypotension.

BACKGROUND: Reversible cerebral vasoconstriction syndrome (RCVS) and posterior reversible encephalopathy syndrome (PRES) are both rare disorders. The pathophysiology of both diseases is not yet fully understood. METHODS: We report the unique case of a 19-year-old comatose woman who was brought to the ER after a series of generalized tonic-clonic seizures 6 days post peridural anesthesia for cesarean section. Vital signs and initial laboratory testing including urine analysis and drug screening were unremarkable. Initial cranial CT scan showed an acute small subdural hematoma (17 mm length × 6 mm width × 30 mm height), cerebral edema with slit ventricles, and slight cerebellar tonsillar herniation as signs of intracranial hypotension. CT angiography depicted narrowing of the proximal intracranial vessels consistent with RCVS. MR imaging was also suggestive of both intracranial hypotension and RCVS and showed, in addition, vasogenic edema consistent with PRES. An extensive CSF leakage involving T1 to L2/L3 was confirmed by spinal MRI. RESULTS: The patient underwent conservative therapy for intracranial hypotension (e.g., head-down position) as well as epidural blood patch, which led to regression of the clinical symptoms within a few days. Follow-up MRI showed complete resolution of all radiological changes. CONCLUSIONS: In summary, our patient developed clinical and neuroradiological signs of intracranial hypotension and a combination of PRES and RCVS associated with a CSF leakage caused by peridural anesthesia; by treating the intracranial hypotension, the other syndromes resolved. From a clinical point of view, it is important to look for CSF leakage as a treatable possible cause of PRES and/or RCVS triggered by intracranial hypotension as in our patient postpartum. Moreover, it is vital to obtain a good history as, in cases of suspected CSF leakage with classic postural headache, a recent spinal/cranial procedure is typically present.

Challenges of bacterial meningitis case management in low income settings: an experience from Ethiopia.

OBJECTIVE: To investigate the current diagnostic and therapeutic strategies used in the care of patients with suspected bacterial meningitis at teaching hospitals in Ethiopia. METHODS: This was a hospital-based retrospective study conducted at four teaching hospitals in different regions of Ethiopia. Participants were patients aged 14 years and older treated for suspected bacterial meningitis. Presenting complaints, diagnostic strategies used and treatments given were obtained from clinical records. RESULT: A total of 425 patients were included in the study; 52.7% were men and 83.8% were younger than 50 years. Fever, headache, neck stiffness and impaired consciousness were the most common clinical presentations; 55.5% underwent lumbar puncture. Overall, only 96 (22.6%) patients had cerebrospinal fluid abnormalities compatible with bacterial meningitis. A causative bacterium was identified in only 14 cases. Ceftriaxone was used as the empiric treatment of choice, either alone or in combination with other antibiotics; 17.6% of patients were also given vancomycin. Adjunctive dexamethasone was given to 50.4%. CONCLUSION: Most patients treated as bacterial meningitis did not receive a proper diagnostic workup. The choice of antibiotic was not tailored to the specific clinical condition of the patient. Such an approach may result in poor treatment outcomes and lead to antibiotic resistance. Management of patients with suspected bacterial meningitis should be supported by analysis of cerebrospinal fluid, and treatment should be tailored to local evidence and current evidence-based recommendations.

Adjunctive dexamethasone therapy in unconfirmed bacterial meningitis in resource limited settings: is it a risk worth taking?

BACKGROUND: Bacterial meningitis is associated with significant morbidity and mortality despite advances in medical care. The main objective of this study was to assess the association of adjunctive dexamethasone treatment with discharge outcome of patients treated as bacterial meningitis in low income setting. METHODS: A retrospective study was conducted at four teaching hospitals across Ethiopia. Patients of age 14 years and older treated as cases of bacterial meningitis between January 1, 2011 and April 30, 2015 were included in this study. Information regarding sociodemographic data, clinical presentations, laboratory data, treatments given and status at hospital discharge were retrieved from patients' medical records using a structured questionnaire. Predefined outcome variables at discharge were analysed using descriptive statistics. Multivariable logistic regression was used to identify factors independently associated with poor outcome. RESULTS: A total of 425 patients treated with the presumptive clinical diagnosis of bacterial meningitis were included in this study (lumbar puncture done in 56 %; only 19 % had CSF findings compatible with bacterial meningitis, and only 3 % had proven etiology). The overall in hospital mortality rate was 20.2 %. Impaired consciousness, aspiration pneumonia, and cranial nerve palsy at admission were independently associated with increased mortality. Adjuvant dexamethasone, which was used in 50.4 % of patients, was associated with increased in-hospital mortality (AOR = 3.38; 95 % CI 1.87-6.12, p < 0.001) and low Glasgow outcome scale (GOS) at discharge (AOR = 4.46 (95 % CI 1.98-10.08). This association between dexamethasone and unfavorable outcome was found to be more pronounced in suspected but unproven cases and in those without CSF alterations compatible with bacterial meningitis. CONCLUSION: Most patients treated for suspected bacterial meningitis did not receive proper diagnostic workup. Adjuvant dexamethasone use in clinically suspected but unproven cases of bacterial meningitis was associated with an increased mortality and poor discharge GOS. These findings show that there are potential deleterious effects in unconfirmed cases in this setting. Physicians practising under such circumstances should thus abide with the current recommendation and defer the use of adjuvant corticosteroid in suspected cases of bacterial meningitis.

Dramatic reduction of mortality in pneumococcal meningitis.

BACKGROUND: Acute bacterial meningitis is still a life threatening disease. METHODS: We performed a retrospective observational study on the clinical characteristics of consecutively admitted patients with acute pneumococcal meningitis in a single tertiary care center in central Europe (from 2003 until 2015). Data were compared with a previously published historical group of 87 patients treated for pneumococcal meningitis at the same hospital (from 1984 until 2002). RESULTS: Fifty-five consecutive patients with microbiologically proven pneumococcal meningitis were included. Most striking, mortality was down to 5.5 %, which was significantly lower than in the historical group where 24.1 % of the patients did not survive. Intracranial complications during the course of the disease were common and affected half of the patients. Unlike in the historic group, most of the intracranial complications (except ischemic stroke) were no longer associated with a low Glasgow Outcome Score at discharge. CONCLUSION: The drastic reduction of mortality proves there have been important advances in the treatment of pneumococcal meningitis. Nevertheless, the fact that only 44.2 % of survivors had a full recovery indicates that the search for new adjunctive treatment options must be ongoing.

Myeloid-related protein 14 promotes inflammation and injury in meningitis.

BACKGROUND: Neutrophilic inflammation often persists for days despite effective antibiotic treatment and contributes to brain damage in bacterial meningitis. We propose here that myeloid-related protein 14 (MRP14), an abundant cytosolic protein in myeloid cells, acts as an endogenous danger signal, driving inflammation and aggravating tissue injury. METHODS: The release pattern of MRP14 was analyzed in human and murine cerebrospinal fluid (CSF), as well as in isolated neutrophils. Its functional role was assessed in a mouse meningitis model, using MRP14-deficient mice. RESULTS: We detected large quantities of MRP14 in CSF specimens from patients and mice with pneumococcal meningitis. Immunohistochemical analyses and a cell-depletion approach indicated neutrophils as the major source of MRP14. In a meningitis model, MRP14-deficient mice showed a better resolution of inflammation during antibiotic therapy, which was accompanied by reduced disease severity. Intrathecal administration of MRP14 before infection reverted the phenotype of MRP14-deficient mice back to wild type. Moreover, intrathecal injection of MRP14 alone was sufficient to induce meningitis in a Toll-like receptor 4 (TLR4)-CXCL2-dependent manner. Finally, treatment with the MRP14 antagonist paquinimod reduced inflammation and disease severity significantly, reaching levels comparable to those achieved after genetic depletion of MRP14. CONCLUSIONS: The present study implicates MRP14 as an essential propagator of inflammation and potential therapeutic target in pneumococcal meningitis.

Plasminogen activator inhibitor-1 influences cerebrovascular complications and death in pneumococcal meningitis.

Cerebrovascular complications are common in pneumococcal meningitis and are a main determinant of unfavourable outcome and death. We hypothesized that plasminogen activator inhibitor-1 (PAI-1) is a major contributor to cerebrovascular complications and death in pneumococcal meningitis. In a nationwide prospective cohort study we evaluated the effect of the 4G/5G polymorphism (rs1799889) in SERPINE1 (coding for PAI-1) on cerebrovascular complications and outcome in adults with pneumococcal meningitis proven by cerebrospinal fluid (CSF) culture. From 2006 to 2011, a total of 991 adult patients with community-acquired bacterial meningitis were included in the cohort and 712 had pneumococcal meningitis. The rs1799889 5G/5G genotype was associated with an increased risk of unfavourable outcome [odds ratio (OR) 1.69, 95 % confidence interval (CI) 1.03-2.78] and mortality (OR 2.20, 95 % CI 1.02-4.86) in white adults with pneumococcal meningitis. rs1799889 was associated with CSF PAI-1 concentrations (P = 0.048), and white patients homozygous for the low PAI-1 producing genotype (5G/5G) had a significantly higher risk for cerebral infarctions (P = 0.015) and haemorrhages (P = 0.005). Subsequently, we assessed the functionality of PAI-1 in a pneumococcal meningitis mouse model, using Serpine1 knockout mice. Consistent with the human data, Serpine1-deficient mice had increased mortality and cerebral haemorrhages compared to wild-type mice. We conclude PAI-1 is protective for death in humans and mice with pneumococcal meningitis by reducing cerebrovascular complications.

High mobility group box 1 prolongs inflammation and worsens disease in pneumococcal meningitis.

Neutrophilic inflammation, which often persists over days despite appropriate antibiotic therapy, contributes substantially to brain damage in bacterial meningitis. We hypothesized that persistent inflammation is the consequence of a vicious cycle in which inflammation-induced cell injury leads to the release of endogenous danger molecules (e.g. high mobility group box 1) that drive the inflammatory response, causing further damage. The present study aimed to assess the mechanisms of high mobility group box 1 protein release and its functional relevance for the development and progression of pneumococcal meningitis. High mobility group box 1 was found in large quantities in cerebrospinal fluid samples of patients and mice with pneumococcal meningitis (predominantly in advanced stages of the disease). By using macrophages, we demonstrated that the release of high mobility group box 1 from macrophages following pneumococcal challenge is passive in nature and probably not connected with inflammasome- and oxidative stress-dependent inflammatory cell death forms. In a mouse meningitis model, treatment with the high mobility group box 1 antagonists ethyl pyruvate or Box A protein had no effect on the development of meningitis, but led to better resolution of inflammation during antibiotic therapy, which was accompanied by reduced brain pathology and better disease outcome. Additional experiments using gene-deficient mice and murine neutrophils provided evidence that high mobility group box 1 acts as a chemoattractant for neutrophils in a receptor for advanced glycosylation end products-dependent fashion. In conclusion, the present study implicated high mobility group box 1, likely released from dying cells, as a central propagator of inflammation in pneumococcal meningitis. Because persistent inflammation contributes to meningitis-associated brain damage, high mobility group box 1 may represent a promising target for adjunctive therapy of this disease.

Combining antibiotic with anti-TLR2/TLR13 therapy prevents brain pathology in pneumococcal meningitis.

Despite effective antibiotic therapy, brain-destructive inflammation often cannot be avoided in pneumococcal meningitis. The causative signals are mediated predominantly through TLR-recruited myeloid differentiation primary response adaptor 88 (MyD88), as indicated by a dramatic pneumococcal meningitis phenotype of Myd88-/- mice. Because lipoproteins and single-stranded RNA are crucial for recognition of Gram-positive bacteria such as Streptococcus pneumoniae by the host immune system, we comparatively analyzed the disease courses of Myd88-/- and Tlr2-/- Tlr13-/- mice. Their phenotypic resemblance indicated TLR2 and -13 as master sensors of S. pneumoniae in the cerebrospinal fluid. A neutralizing anti-TLR2 antibody (T2.5) and chloroquine (CQ) - the latter applied here as an inhibitor of murine TLR13 and its human ortholog TLR8 - abrogated activation of murine and human primary immune cells exposed to antibiotic-treated S. pneumoniae. The inhibitory effect of the T2.5/CQ cocktail was stronger than that of dexamethasone, the current standard adjunctive drug for pneumococcal meningitis. Accordingly, TLR2/TLR13 blockade concomitant with ceftriaxone application significantly improved the clinical course of pneumococcal meningitis compared with treatment with ceftriaxone alone or in combination with dexamethasone. Our study indicates the importance of murine TLR13 and human TLR8, besides TLR2, in pneumococcal meningitis pathology, and suggests their blockade as a promising antibiotic therapy adjunct.

Adjunctive N-acetyl-L-cysteine in treatment of murine pneumococcal meningitis.

Despite antibiotic therapy, acute and long-term complications are still frequent in pneumococcal meningitis. One important trigger of these complications is oxidative stress, and adjunctive antioxidant treatment with N-acetyl-l-cysteine was suggested to be protective in experimental pneumococcal meningitis. However, studies of effects on neurological long-term sequelae are limited. Here, we investigated the impact of adjunctive N-acetyl-l-cysteine on long-term neurological deficits in a mouse model of meningitis. C57BL/6 mice were intracisternally infected with Streptococcus pneumoniae. Eighteen hours after infection, mice were treated with a combination of ceftriaxone and placebo or ceftriaxone and N-acetyl-l-cysteine, respectively. Two weeks after infection, neurologic deficits were assessed using a clinical score, an open field test (explorative activity), a t-maze test (memory function), and auditory brain stem responses (hearing loss). Furthermore, cochlear histomorphological correlates of hearing loss were assessed. Adjunctive N-acetyl-l-cysteine reduced hearing loss after pneumococcal meningitis, but the effect was minor. There was no significant benefit of adjunctive N-acetyl-l-cysteine treatment in regard to other long-term complications of pneumococcal meningitis. Cochlear morphological correlates of meningitis-associated hearing loss were not reduced by adjunctive N-acetyl-l-cysteine. In conclusion, adjunctive therapy with N-acetyl-l-cysteine at a dosage of 300 mg/kg of body weight intraperitoneally for 4 days reduced hearing loss but not other neurologic deficits after pneumococcal meningitis in mice. These results make a clinical therapeutic benefit of N-acetyl-l-cysteine in the treatment of patients with pneumococcal meningitis questionable.