Procoagulant and fibrinolytic activity in cerebrospinal fluid from adults with bacterial meningitis

Comparison of D-dimer concentration and thromboelastography for diagnosis of cerebrovascular accidents in dogs: A retrospective study

BACKGROUND

Cerebrovascular accidents (CVAs) in dogs are diagnosed using magnetic resonance imaging (MRI). This modality is sometimes unavailable, and CVAs can resemble other lesions on MRI. D-dimer concentration and thromboelastography (TEG) are utilized in human medicine in addition to diagnostic imaging to support diagnosis of CVAs, but their use in veterinary patients has not been assessed.

OBJECTIVE

Assess utility of blood D-dimer concentration and TEG in supporting the imaging diagnosis of CVAs in dogs.

ANIMALS

Sixty-eight client-owned dogs with neurologic signs that had brain MRI and D-dimer concentration or TEG performed.

METHODS

Multicenter, retrospective study. The incidence of abnormal D-dimer concentration or TEG was compared between patients with MRI evidence of CVA and a control population. Analysis methods included Fisher's exact test or Chi-squared test for association and comparison of independent proportions.

RESULTS

Neither D-dimer concentration nor TEG was significantly associated with a CVA (P = .38 and .2, respectively). D-dimer testing was performed in a low-risk population and showed low sensitivity (30.8%; 95% confidence interval [CI], 10%-61%) and high specificity (86.4%; 95% CI, 64%-96%) for CVA diagnosis. Thromboelastography was performed in a high-risk population and showed moderate sensitivity (64.3%; 95% CI, 44%-81%) and specificity (66.7%; 95% CI, 24%-94%) for CVA diagnosis. Abnormal D-dimer concentration or TEG were not helpful in differentiating hemorrhagic from ischemic stroke (P = .43 and .41, respectively).

CONCLUSIONS

Although blood D-dimer concentration or TEG alone are not diagnostic of CVAs in dogs, a positive D-dimer result supports additional testing for CVA.

Cerebrovascular complications in patients with community-acquired bacterial meningitis: occurrence and associated factors in the COMBAT multicenter prospective cohort

BACKGROUND

Community-acquired bacterial meningitis is a rare but severe central nervous system infection that may be associated with cerebrovascular complications (CVC). Our objective is to assess the prevalence of CVC in patients with community-acquired bacterial meningitis and to determine the first-48 h factors associated with CVC.

METHODS

We analyzed data from the prospective multicenter cohort study (COMBAT) including, between February 2013 and July 2015, adults with community-acquired bacterial meningitis. CVC were defined by the presence of clinical or radiological signs (on cerebral CT or MRI) of focal clinical symptom. Factors associated with CVC were identified by multivariate logistic regression.

RESULTS

CVC occurred in 128 (25.3%) of the 506 patients in the COMBAT cohort (78 (29.4%) of the 265 pneumococcal meningitis, 17 (15.3%) of the 111 meningococcal meningitis, and 29 (24.8%) of the 117 meningitis caused by other bacteria). The proportion of patients receiving adjunctive dexamethasone was not statistically different between patients with and without CVC (p = 0.84). In the multivariate analysis, advanced age (OR = 1.01 [1.00-1.03], p = 0.03), altered mental status at admission (OR = 2.23 [1.21-4.10], p = 0.01) and seizure during the first 48 h from admission (OR = 1.90 [1.01-3.52], p = 0.04) were independently associated with CVC.

CONCLUSIONS

CVC were frequent during community-acquired bacterial meningitis and associated with advanced age, altered mental status and seizures occurring within 48 h from admission but not with adjunctive corticosteroids.

Human Listeriosis

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

Stroke in Patients with Bacterial Meningitis: A Cohort Study and Meta-Analysis

OBJECTIVE

The purpose of this study was to characterize patients with ischemic stroke due to bacterial meningitis.

METHODS

In a single-center retrospective study, we analyzed 102 patients with bacterial meningitis of which 19 had an ischemic stroke. Clinical characteristics, cerebrospinal fluid (CSF) analyses, and spatiotemporal distribution of infarcts were assessed. In addition, we searched PubMed from database inception to August 2021 for observational studies on ischemic stroke in patients with bacterial meningitis, and performed a meta-analysis to investigate the frequency and timing of stroke as well as its effect on mortality.

RESULTS

In our cohort, 15 (78.9%) patients with stroke had an modified Rankin scale (mRS)  ≥ $$ \ge $$  3 at discharge compared to 33 (39.8%) in patients without stroke (p < 0.01). Of 1,692 patients with bacterial meningitis from 15 cohort studies included in our meta-analysis, cerebral infarcts were found in 332 (16%, 95% confidence interval [CI] = 0.13-0.20) patients. The occurrence of stroke was strongly associated with a higher mortality (odds ratio [OR] = 2.38, 95% CI = 1.70-3.34, p < 0.0001). There was no association of any specific causative pathogen with the occurrence of stroke. Infarcts were mainly distributed in territories of arteries located in the vicinity to the infection focus and peaked at 3 to -7 days and at 2 weeks after onset of meningitis. In patients with ischemic stroke, vasculopathy was found in 63.2% and additional intracerebral hemorrhage in 15.8%.

INTERPRETATION

This study found that ischemic stroke due to bacterial meningitis is caused by cerebral vasculopathy located in the vicinity of the infection focus, and that the time course of infarctions might enable a therapeutic intervention. ANN NEUROL 2023.

The role of plasminogen activator inhibitor-2 in pneumococcal meningitis

Pneumococcal meningitis is associated with dysregulation of the coagulation cascade. Previously, we detected upregulation of cerebral plasminogen activator inhibitor-2 (PAI-2) mRNA expression during pneumococcal meningitis. Diverse functions have been ascribed to PAI-2, but its role remains unclear. We analyzed the function of SERPINB2 (coding for PAI-2) in patients with bacterial meningitis, in a well-established pneumococcal meningitis mouse model, using Serpinb2 knockout mice, and in vitro in wt and PAI-2-deficient bone marrow-derived macrophages (BMDMs). We measured PAI-2 in cerebrospinal fluid of patients, and performed functional, histopathological, protein and mRNA expression analyses in vivo and in vitro. We found a substantial increase of PAI-2 concentration in CSF of patients with pneumococcal meningitis, and up-regulation and increased release of PAI-2 in mice. PAI-2 deficiency was associated with increased mortality in murine pneumococcal meningitis and cerebral hemorrhages. Serpinb2−/− mice exhibited increased C5a levels, but decreased IL-10 levels in the brain during pneumococcal infection. Our in vitro experiments confirmed increased expression and release of PAI-2 by wt BMDM and decreased IL-10 liberation by PAI-2-deficient BMDM upon pneumococcal challenge. Our data show that PAI-2 is elevated during in pneumococcal meningitis in humans and mice. PAI-2 deficiency causes an inflammatory imbalance, resulting in increased brain pathology and mortality.

Measurement of D-dimer in cerebrospinal fluid using a luminescent oxygen channeling immunoassay

Background

Measurement of D-dimer in cerebrospinal fluid (CSF) allows insight into coagulation system activation in the central nervous system and can be utilized to monitor intracranial hemorrhage as well as acute phase processes beyond hemostasis in inflammatory and neoplastic diseases. So far, the measurability of D-dimer in low and very low concentrations in CSF was limited in conventional immunoassays. Novel high-sensitivity chemiluminescent immunoassays such as the luminescent oxygen channeling immunoassay (LOCI^®) are getting increasingly available but have not been validated in CSF. The aim of this study was to investigate the accuracy and linearity of the LOCI^® in assessing D-dimer in CSF.

Methods

INNOVANCE LOCI hs D-dimer reagent cartridge was used for the measurement of D-dimer in CSF of patients with different neurological diseases. For the evaluation of linearity, dilution series were performed in a pooled CSF sample with the determination of intra-assay precision (CV, coefficient of variation) in 3 individual samples with 20 replicates. Furthermore, D-dimer concentrations measured by LOCI^® were compared with the respective results of a routinely available clinical latex-enhanced immunoassay (HemosiIL D-Dimer HS 500).

Results

Linear regression analysis of the LOCI^® method revealed a r² of 1.00 (p < 0.001) with a regression coefficient B of 1.012 ± 0.003 (CI: 1.005–1.019, p < 0.001) and an intercept of −1.475 ± 1.309 (CI: −4.493 to 1.543); the median intra-assay CV was 0.69% (range: 0.68–0.75). In total, 185 CSF samples were measured by LOCI^® technology, showing a mean concentration of 204.84 ± 2,214.93 ng/ml. D-dimer concentration between LOCI and latex-enhanced immunoassay differed by a factor of 10.6 ± 13.6 on average with a maximum deviation by a factor of 61.3; the maximum deviation was found at low concentrations.

Conclusion

D-dimer in CSF of patients with neurological disease can be reliably measured by the LOCI^® method with high linearity and accuracy at low concentrations.

Analysis of CSF D-Dimer to Identify Intrathecal Fibrin-Driven Autoimmunity in Patients With Multiple Sclerosis

Background and Objectives

Proteins of the coagulation system contribute to autoimmune inflammation in patients with multiple sclerosis (MS). On blood-brain barrier (BBB) disruption, fibrinogen enters the CNS and is rapidly converted to fibrin, unfolding pleiotropic autoimmune mechanisms. Fibrin accumulation leads to subsequent proteolytic degradation that results in D-dimer generation. The primary objective of this study was to determine intrathecal levels of D-dimer in CSF as a measure of intrathecal coagulation cascade activation and to evaluate its diagnostic utility in patients with MS in contrast to healthy subjects. Key secondary objectives included analysis of CSF D-dimer in differential diagnoses of MS and its relation to routine clinical markers of disease activity.

Methods

Patients admitted for the assessment of suspected MS were prospectively recruited from October 2017 to December 2020. Blood plasma and citrated CSF samples were analyzed using a highly sensitive luminescent oxygen channeling immunoassay. Intrathecal generation of D-dimer was analyzed by adjusting for CSF/serum albumin (Q_alb) and CSF/plasma D-dimer quotients (Q_D-dimer), and corresponding CSF fibrinogen levels were determined. Final diagnoses after full evaluation and clinical data were recorded.

Results

Of 187 patients, 113 patients received a diagnosis of MS or clinically/radiologically isolated syndrome. We found increased intrathecal CSF D-dimer generation levels (Q_D-dimer/Q_alb-index) for patients with relapsing-remitting MS (RRMS; n = 71, median 4.7, interquartile range [IQR] 2.5–8.0) when compared with those for disease controls (n = 22, median 2.6, IQR 2.1–4.8, p = 0.031). Absolute CSF D-dimer values correlated with CSF fibrinogen levels (r = 0.463; p < 0 .001) and CSF leukocytes (r = 0.273; p = 0.003) and were elevated in MS patients with contrast enhancement (CE) compared with MS patients without CE on MRI (n = 48, median 6 ng/mL, and IQR 3–15.25 vs n = 41, median 4 ng/mL, and IQR 2–7; p = 0.026). Exploratory subgroup analyses indicated a correlation of intrathecal inflammatory activity and CSF D-dimer levels.

Discussion

D-dimer in CSF can be reliably determined and correlates with markers of CNS inflammation and CSF fibrinogen levels. Adjusted for BBB dysfunction, CSF D-dimer may allow the identification of intrathecal coagulation cascade activation in patients with MS.

Classification of Evidence

This study provides Class I evidence that CSF D-dimer levels are elevated in patients with RRMS.

D-Dimer Combined With CRP Can Improve the Differential Value of Bacterial Meningitis and Tuberculous Meningitis

OBJECTIVE

To explore the diagnostic value of the coagulation marker D-dimer and its combination with the traditional marker C-reactive protein (CRP) in distinguishing bacterial meningitis (BM) from tuberculous meningitis (TM).

METHODS

We performed a retrospective study on specimens from 173 patients with meningitis who were hospitalized at the First Affiliated Hospital of Guangxi Medical University, Guangxi, China, from 2012 through 2020. The patient records were divided into the BM group and the TM group, and hematological parameters D-dimer and CRP were evaluated for the 2 groups.

RESULTS

The levels of D-dimer and CRP in the BM group were significantly higher than those levels in the TM group (P ˂.001 for each), and the sensitivity and specificity of the combined detection of the 2 markers was 86.3% to 100%; the area under the receiver operating characteristic (ROC) curve reached 0.983 (95% confidence interval [CI], 0.966-0.999).

CONCLUSION

D-dimer testing has high specificity in distinguishing between BM and TM; CRP testing also has high sensitivity. The combined diagnosis of the 2 biomarkers helps to distinguish TM from BM.

The Potentials of Melatonin in the Prevention and Treatment of Bacterial Meningitis Disease

Bacterial meningitis (BM) is an acute infectious central nervous system (CNS) disease worldwide, occurring with 50% of the survivors left with a long-term serious sequela. Acute bacterial meningitis is more prevalent in resource-poor than resource-rich areas. The pathogenesis of BM involves complex mechanisms that are related to bacterial survival and multiplication in the bloodstream, increased permeability of blood-brain barrier (BBB), oxidative stress, and excessive inflammatory response in CNS. Considering drug-resistant bacteria increases the difficulty of meningitis treatment and the vaccine also has been limited to several serotypes, and the morbidity rate of BM still is very high. With recent development in neurology, there is promising progress for drug supplements of effectively preventing and treating BM. Several in vivo and in vitro studies have elaborated on understanding the significant mechanism of melatonin on BM. Melatonin is mainly secreted in the pineal gland and can cross the BBB. Melatonin and its metabolite have been reported as effective antioxidants and anti-inflammation, which are potentially useful as prevention and treatment therapy of BM. In bacterial meningitis, melatonin can play multiple protection effects in BM through various mechanisms, including immune response, antibacterial ability, the protection of BBB integrity, free radical scavenging, anti-inflammation, signaling pathways, and gut microbiome. This manuscript summarizes the major neuroprotective mechanisms of melatonin and explores the potential prevention and treatment approaches aimed at reducing morbidity and alleviating nerve injury of BM.

Markers for neural degeneration and regeneration: novel highly sensitive methods for the measurement of thrombin and activated protein C in human cerebrospinal fluid

Inflammation and coagulation are tightly interconnected in the pathophysiology of neuronal diseases. Thrombin, a pro-coagulant serine protease is associated with neurodegeneration and its indirect inhibitor, activated protein C (aPC), is considered neuroprotective. While levels of thrombin and aPC activity are readily measured in the blood, similar assays in the cerebrospinal fluid (CSF) have not been described. The aim of this study was to establish a specific and sensitive enzymatic assay to measure both thrombin and aPC activity in the CSF. CSF was collected from 14 patients with suspected normal pressure hydrocephalus served as a control group, while seven patients with central nervous system infections served as an acute neuro-inflammatory study group and one sample of CSF following traumatic lumbar puncture served as a positive control. Thrombin and aPC activities were measured by fluorescence released by specific proteolytic cleavage in the presence of endopeptidase and amino-peptidase inhibitors to ensure specificity. Specificity of the method was verified by thrombin and serine-protease inhibitors N-alpha-((2-naphthylsulfinyl)glycyl)-DL-p-amidinophenylalanylpiperidine and phenylmethanesulfonyl fluoride. Inhibition of thrombin activity by CSF samples and levels of specific thrombin inhibitors were also assessed. Thrombin and aPC activities were reliably measured and were significantly higher in the CSF of patients with central nervous system infections compared to normal pressure hydrocephalus controls, suggesting the involvement of these factors in neuro-inflammation. CSF thrombin activity levels in the presence of known thrombin concentration were high in patients with central nervous system infections, and low in normal pressure hydrocephalus patients. Quantification of endogenous thrombin inhibitors protease nexin 1, amyloid precursor protein and anti-thrombin III in CSF by western blot indicated a significant elevation of amyloid precursor protein in infectious CSF. In conclusion, this study describes a novel and sensitive assay aimed at the detection of thrombin and aPC activity in CSF. This method may be useful for measuring these factors that reflect degenerative and protective influences of coagulation on neurological disorders. The study procedure was approved by the Ethics Committee of the Chaim Sheba Medical Center (approval No. 4245-17-SMC) on October 18, 2018.

Characterization of a Listeria monocytogenes meningitis mouse model

BACKGROUND

Listeria monocytogenes is a common cause of bacterial meningitis. We developed an animal model of listerial meningitis.

METHODS

In survival studies, C57BL/6 mice received intracisternal injections with different L. monocytogenes sequence type 1 (ST1) colony forming units per milliliter (CFU; n = 48, 105, 106, 107, 108, and 109 CFU/ml). Second, mice were inoculated with 108 CFU/ml ST1 and sacrificed at 6 h and 24 h (n = 12/group). Outcome parameters were clinical score, CFUs, cyto- and chemokine levels, and brain histopathology. Third, 84 mice were inoculated (109 CFU/ml ST1) to determine optimal antibiotic treatment with different doses of amoxicillin and gentamicin. Fourth, mice were inoculated with 109 CFU/ml ST1, treated with amoxicillin, and sacrificed at 16 h and 24 h (n = 12/group) for outcome assessment. Finally, time point experiments were repeated with ST6 (n = 24/group).

RESULTS

Median survival time for inoculation with 108 and 109 CFU/ml ST1 was 46 h and 40 h; lower doses of bacteria led to minimal clinical signs of disease. Brain levels of IL-6, IL-17A, and IFN-γ were elevated at 24 h, and IL-1β, IL-6, IL-10, IFN-γ, and TNF-α were elevated in blood at 6 h and 24 h. Histopathology showed increased meningeal infiltration, vascular inflammation of meningeal vessels, hemorrhages, and ventriculitis. In the treatment model, brain levels of IL-6 and IL-17A and blood levels of IL-6 and IFN-γ were elevated. Compared to ST6, infection with ST1 led initially to higher levels of IL-1β and TNF-α in blood and more profound neuropathological damage. At 16 h post inoculation, IL-1β, IL-10, and TNF-α in blood and IL-6, IL17A, TNF-α, and IFN-γ levels in brain were higher in ST1 compared to ST6 without differences in CFUs between STs. At 24 h, neuropathology score was higher in ST1 compared to ST6 (p = 0.002) infected mice.

CONCLUSIONS

We developed and validated a murine model of listerial meningitis. ST1-infected mice had a more severe inflammatory response and brain damage as compared to ST6-infected mice.

Variation in coagulation and fibrinolysis genes evaluated for their contribution to cerebrovascular complications in adults with bacterial meningitis in the Netherlands

OBJECTIVE

To study whether genetic variation in coagulation and fibrinolysis genes contributes to cerebrovascular complications in bacterial meningitis.

METHODS

We performed a nationwide prospective genetic association study in adult community-acquired bacterial meningitis patients. The exons and flanking regions of 16 candidate genes involved in coagulation and fibrinolysis pathways were sequenced. We analyzed whether genetic variation in these genes resulted in a higher risk of cerebrovascular complications, unfavorable outcome and differences in thrombocyte count on admission.

RESULTS

From 2006 to 2011, a total of 1101 bacterial meningitis patients were identified of whom 622 supplied DNA for genotyping and passed genetic quality control steps. In 139 patients (22%) the episode of bacterial meningitis was complicated by cerebral infarction, and 188 (30%) had an unfavorable outcome. We identified the functional variant rs494860 in the protein Z (PROZ) gene as our strongest association with occurrence of cerebral infarction (odds ratio (OR) 0.49 (95% confidence interval 0.33-0.73), p = 5.2 × 10^-4). After Bonferroni correction for multiple testing no genetic variant was significantly associated (p-value threshold 2.7 × 10^-4).

CONCLUSION

Our study suggests a functional genetic variation in the PROZ gene, rs494860, may be of importance in bacterial meningitis pathogenesis and cerebral infarction risk. Replication of this finding in other cohort studies populations is needed.

Role of neural barriers in the pathogenesis and outcome of Streptococcus pneumoniae meningitis

Bacterial meningitis is an inflammatory disease of the meninges of the central nervous system (CNS). Streptococcus pneumoniae (S. pneumoniae), Neisseria meningitidis, and Haemophilus influenzae are the major bacterial pathogens causing meningitis with S. pneumoniae being responsible for two thirds of meningitis cases in the developed world. To reach the CNS following nasopharyngeal colonization and bacteraemia, the bacteria traverse from the circulation across the blood brain barrier (BBB) and choroid plexus. While the BBB has a protective role in healthy individuals by shielding the CNS from neurotoxic substances circulating in the blood and maintaining the homeostasis within the brain environment, dysfunction of the BBB is associated with the pathophysiology of numerous neurologic disorders, including bacterial meningitis. Inflammatory processes, including release of a broad range of cytokines and free radicals, further increase vascular permeability and contribute to the excessive neural damage observed. Injury to the cerebral microvasculature and loss of blood flow auto-regulation promote increased intracranial pressure and may lead to vascular occlusion. Other common complications commonly associated with meningitis include abnormal neuronal hyper-excitability (e.g., seizures) and loss of hearing. Despite the existence of antibiotic treatment and adjuvant therapy, the relatively high mortality rate and the severe outcomes among survivors of pneumococcal meningitis in developing and developed countries increase the urgency in the requirement of discovering novel biomarkers for the early diagnosis as well as novel treatment approaches. The present review aimed to explore the changes in the brain vascular barriers, which allow S. pneumoniae to invade the CNS, and describe the resultant brain injuries following bacterial meningitis.

Neurological sequelae of bacterial meningitis

OBJECTIVES

We reported on occurrence and impact of neurological sequelae after bacterial meningitis.

METHODS

We reviewed occurrence of neurological sequelae in children and adults after pneumococcal and meningococcal meningitis.

RESULTS

Most frequently reported sequelae are focal neurological deficits, hearing loss, cognitive impairment and epilepsy. Adults with pneumococcal meningitis have the highest risk of developing focal neurological deficits, which are most commonly caused by cerebral infarction, but can also be due to cerebritis, subdural empyema, cerebral abscess or intracerebral bleeding. Focal deficits may improve during clinical course and even after discharge, but a proportion of patients will have persisting focal neurological deficits that often interfere in patient's daily life. Hearing loss occurs in a high proportion of patients with pneumococcal meningitis and has been associated with co-existing otitis. Children and adults recovering from bacterial meningitis without apparent neurological deficits are at risk for long-term cognitive deficits. Early identification of neurological sequelae is important for children to prevent additional developmental delay, and for adults to achieve successful return in society after the disease.

CONCLUSIONS

Neurological sequelae occur in a substantial amount of patients following bacterial meningitis. Most frequently reported sequelae are focal neurological deficits, hearing loss, cognitive impairment and epilepsy.

[Ischemic changes and blood coagulation abnormalities as complications of pneumococcal meningitis]

One explanation for cerebral infarctions that occur as a complication of pneumococcal meningitis is blood coagulation abnormalities. We investigated the clinical features, laboratory test results, magnetic resonance imaging (MRI) findings, and pathological features of 10 patients with pneumococcal meningitis between 2006 and 2013 to examine the abnormal findings that may be associated with prognosis. Five patients (50%) that had Glasgow Outcome Scale scores between 1 and 4 were classified as the poor outcome group. In this group, the MRI revealed a high signal intensity on the diffusion-weighted image (DWI), and there was an abnormal signal along the cerebral cortex and Virchow-Robin spaces, which were characterized pathologically by ischemic changes. The plasma thrombin-antithrombin complex (TAT) levels showed greater differences between the poor and good prognosis groups than platlet and D-dimer levels; this suggested that high plasma TAT levels indicate a poor prognosis.

Comparative proteomics of cerebrospinal fluid reveals a predictive model for differential diagnosis of pneumococcal, meningococcal, and enteroviral meningitis, and novel putative therapeutic targets

BACKGROUND

Meningitis is the inflammation of the meninges in response to infection or chemical agents. While aseptic meningitis, most frequently caused by enteroviruses, is usually benign with a self-limiting course, bacterial meningitis remains associated with high morbidity and mortality rates, despite advances in antimicrobial therapy and intensive care. Fast and accurate differential diagnosis is crucial for assertive choice of the appropriate therapeutic approach for each form of meningitis.

METHODS

We used 2D-PAGE and mass spectrometry to identify the cerebrospinal fluid proteome specifically related to the host response to pneumococcal, meningococcal, and enteroviral meningitis. The disease-specific proteome signatures were inspected by pathway analysis.

RESULTS

Unique cerebrospinal fluid proteome signatures were found to the three aetiological forms of meningitis investigated, and a qualitative predictive model with four protein markers was developed for the differential diagnosis of these diseases. Nevertheless, pathway analysis of the disease-specific proteomes unveiled that Kallikrein-kinin system may play a crucial role in the pathophysiological mechanisms leading to brain damage in bacterial meningitis. Proteins taking part in this cellular process are proposed as putative targets to novel adjunctive therapies.

CONCLUSIONS

Comparative proteomics of cerebrospinal fluid disclosed candidate biomarkers, which were combined in a qualitative and sequential predictive model with potential to improve the differential diagnosis of pneumococcal, meningococcal and enteroviral meningitis. Moreover, we present the first evidence of the possible implication of Kallikrein-kinin system in the pathophysiology of bacterial meningitis.

Antithrombotic therapy for secondary stroke prevention in bacterial meningitis in children

OBJECTIVE

To assess the safety and efficacy of antithrombotic therapy (ATT) for secondary stroke prevention of childhood bacterial meningitis.

STUDY DESIGN

A retrospective study of cases of stroke associated with bacterial meningitis in 2 pediatric hospitals during a period of 15 years. Patients were included in the study if they were between 28 days and 18 years of age and had at least 2 serial neuroimaging studies during the acute phase of their illness. The safety of ATT was assessed by the presence or absence of intracranial hemorrhage. Efficacy was assessed by the failure in preventing stroke recurrence. Neurologic outcome was determined by the last documented Pediatric Stroke Outcome Measure score.

RESULTS

Twenty-two cases of childhood bacterial meningitis complicated by stroke were identified. Six cases were treated with heparin after either initial or recurrent infarction. None of the cases receiving heparin had further recurrence. Aspirin (acetylsalicylic acid [ASA]) was started after the initial or after recurrent infarction in 10 cases. Four (40%) had infarctions on ASA; 3 of these patients subsequently received heparin. In the 14 cases in which no ATT was begun, 8 (57%) had further recurrence of infarction. None of the patients, whether receiving heparin or ASA, had intracranial hemorrhage.

CONCLUSION

In this small sample, heparin and ASA appeared to be safe in childhood bacterial meningitis complicated by stroke and may be effective in improving outcome. Heparin may be more effective than aspirin in preventing recurrent infarction.

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.

Procoagulant phospholipids and tissue factor activity in cerebrospinal fluid from patients with intracerebral haemorrhage

Brain contains large amounts of tissue factor, the major initiator of the coagulation cascade. Neuronal apoptosis after intracerebral haemorrhage (ICH) leads to the shedding of procoagulant phospholipids (PPLs). The aim of this study was to investigate the generation of PPL, tissue factor activity (TFa), and D-Dimer (D-Di) in the cerebrospinal fluid (CSF) at the acute phase of ICH in comparison with other brain diseases and to examine the relationship between these factors and the outcome of ICH. CSF was collected from 112 patients within 48 hours of hospital admission. Thirty-one patients with no neurological or biochemical abnormalities were used to establish reference range in the CSF ("controls"). Thirty had suffered an ICH, and 51 other neurological diagnoses [12: ventricular drainage following brain surgery, 13: viral meningitis, 15: bacterial meningitis, and 11 a neurodegenerative disease (NDD)]. PPL was measured using a factor Xa-based coagulation assay and TFa by one home test. PPL, D-Di, and TFa were significantly higher (P < 0.001) in the CSF of patients with ICH than in controls. TFa levels were significantly (P < 0.05) higher in ICH than in patients with meningitides or NDD. Higher levels (P < 0.05) of TFa were observed in patients with ICH who died than in survivors. TFa measurement in the CSF of patients with ICH could constitute a new prognostic marker.

Intracerebral hemorrhages in adults with community associated bacterial meningitis in adults: should we reconsider anticoagulant therapy?

Objective

To study the incidence, clinical presentation and outcome of intracranial hemorrhagic complications in adult patients with community associated bacterial meningitis.

Methods

Nationwide prospective cohort study from all hospitals in the Netherlands, from 1 March 2006, through 31 December 2010.

Results

Of the 860 episodes of bacterial meningitis that were included, 24 were diagnosed with intracranial hemorrhagic complications: 8 upon presentation and 16 during clinical course. Clinical presentation between patients with or without intracranial hemorrhage was similar. Causative bacteria were Streptococcus pneumoniae in 16 patients (67%), Staphylococcus aureus in 5 (21%), Pseudomonas aeruginosa and Listeria monocytogenes both in 1 patient (4%). Occurrence of intracranial hemorrhage was associated with death (63% vs. 15%, P<0.001) and unfavorable outcome (94% vs. 34%, P<0.001). The use of anticoagulants on admission was associated with a higher incidence of intracranial hemorrhages (odds ratio 5.84, 95% confidence interval 2.17–15.76).

Conclusion

Intracranial hemorrhage is a rare but devastating complication in patients with community-associated bacterial meningitis. Since anticoagulant therapy use is associated with increased risk for intracranial hemorrhage, physicians may consider reversing or temporarily discontinuing anticoagulation in patients with bacterial meningitis.

Fibrinolytic activity in cerebrospinal fluid of dogs with different neurological disorders

BACKGROUND

Fibrinolytic activity in cerebrospinal fluid (CSF) is activated in humans by different pathologic processes.

OBJECTIVES

To investigate fibrinolytic activity in the CSF of dogs with neurological disorders by measuring CSF D-dimer concentrations.

ANIMALS

One hundred and sixty-nine dogs with neurological disorders, 7 dogs with systemic inflammatory diseases without central nervous system involvement (SID), and 7 healthy Beagles were included in the study. Dogs with neurological disorders included 11 with steroid-responsive meningitis-arteritis (SRMA), 37 with other inflammatory neurological diseases (INF), 38 with neoplasia affecting the central nervous system (NEO), 28 with spinal compressive disorders (SCC), 15 with idiopathic epilepsy (IE), and 40 with noninflammatory neurological disorders (NON-INF).

METHODS

Prospective observational study. D-dimers and C-reactive protein (CRP) were simultaneously measured in paired CSF and blood samples.

RESULTS

D-dimers and CRP were detected in 79/183 (43%) and in 182/183 (99.5%) CSF samples, respectively. All dogs with IE, SID, and controls had undetectable concentrations of D-dimers in the CSF. CSF D-dimer concentrations were significantly (P < .001) higher in dogs with SRMA than in dogs with other diseases and controls. CSF CRP concentration in dogs with SRMA was significantly (P < .001) higher than in dogs of other groups and controls, except for the SID group. No correlation was found between blood and CSF D-dimer concentrations.

CONCLUSIONS AND CLINICAL IMPORTANCE

Intrathecal fibrinolytic activity seems to be activated in some canine neurological disorders, and it is high in severe meningeal inflammatory diseases. CSF D-dimer concentrations may be considered a diagnostic marker for SRMA.

Characterization of a pneumococcal meningitis mouse model

BACKGROUND

S. pneumoniae is the most common causative agent of meningitis, and is associated with high morbidity and mortality. We aimed to develop an integrated and representative pneumococcal meningitis mouse model resembling the human situation.

METHODS

Adult mice (C57BL/6) were inoculated in the cisterna magna with increasing doses of S. pneumoniae serotype 3 colony forming units (CFU; n = 24, 104, 105, 106 and 107 CFU) and survival studies were performed. Cerebrospinal fluid (CSF), brain, blood, spleen, and lungs were collected. Subsequently, mice were inoculated with 104 CFU S. pneumoniae serotype 3 and sacrificed at 6 (n = 6) and 30 hours (n = 6). Outcome parameters were bacterial outgrowth, clinical score, and cytokine and chemokine levels (using Luminex®) in CSF, blood and brain. Meningeal inflammation, neutrophil infiltration, parenchymal and subarachnoidal hemorrhages, microglial activation and hippocampal apoptosis were assessed in histopathological studies.

RESULTS

Lower doses of bacteria delayed onset of illness and time of death (median survival CFU 104, 56 hrs; 105, 38 hrs, 106, 28 hrs. 107, 24 hrs). Bacterial titers in brain and CSF were similar in all mice at the end-stage of disease independent of inoculation dose, though bacterial outgrowth in the systemic compartment was less at lower inoculation doses. At 30 hours after inoculation with 104 CFU of S. pneumoniae, blood levels of KC, IL6, MIP-2 and IFN- γ were elevated, as were brain homogenate levels of KC, MIP-2, IL-6, IL-1β and RANTES. Brain histology uniformly showed meningeal inflammation at 6 hours, and, neutrophil infiltration, microglial activation, and hippocampal apoptosis at 30 hours. Parenchymal and subarachnoidal and cortical hemorrhages were seen in 5 of 6 and 3 of 6 mice at 6 and 30 hours, respectively.

CONCLUSION

We have developed and validated a murine model of pneumococcal meningitis.

Pathogenesis and pathophysiology of pneumococcal meningitis

Pneumococcal meningitis continues to be associated with high rates of mortality and long-term neurological sequelae. The most common route of infection starts by nasopharyngeal colonization by Streptococcus pneumoniae, which must avoid mucosal entrapment and evade the host immune system after local activation. During invasive disease, pneumococcal epithelial adhesion is followed by bloodstream invasion and activation of the complement and coagulation systems. The release of inflammatory mediators facilitates pneumococcal crossing of the blood-brain barrier into the brain, where the bacteria multiply freely and trigger activation of circulating antigen-presenting cells and resident microglial cells. The resulting massive inflammation leads to further neutrophil recruitment and inflammation, resulting in the well-known features of bacterial meningitis, including cerebrospinal fluid pleocytosis, cochlear damage, cerebral edema, hydrocephalus, and cerebrovascular complications. Experimental animal models continue to further our understanding of the pathophysiology of pneumococcal meningitis and provide the platform for the development of new adjuvant treatments and antimicrobial therapy. This review discusses the most recent views on the pathophysiology of pneumococcal meningitis, as well as potential targets for (adjunctive) therapy.

Diffuse cerebral intravascular coagulation and cerebral infarction in pneumococcal meningitis

BACKGROUND

There is a widely held belief that cerebral infarction after bacterial meningitis is always caused by vasculitis; however, evidence is weak. We hypothesized that diffuse cerebral intravascular coagulation is an additional explanation of cerebral infarction in patients with pneumococcal meningitis.

METHODS

Sixteen brains of adults who died from pneumococcal meningitis were investigated. Clinical data were collected, and brain sections were scored for signs of inflammation and activation of coagulation. Patients with and without cerebral infarction on autopsy were compared.

RESULTS

In total, 38% of patients had focal neurological deficits. Patients died at a median of 7 days (range, 0-32 days) after admission. On autopsy, the nine patients (56%) with cerebral infarctions more often had arterial thrombosis (p = 0.04) than patients without infarction. Patients with infarction tended to have more inflammatory infiltrations of brain parenchyma, microvascular proliferation, small vessel vasculitis/endarteritis obliterans, blood clotting/vessel clogging, and venous thrombosis. None of the patients had large vessel vasculitis. Five patients had cerebral infarctions without vasculitis or endarteritis obliterans. Although four patients with cerebral infarctions had small vessel vasculitis or endarteritis obliterans, areas of infarction could not be localized to the blood flow distribution of these vessels. Blood clotting/vessel clogging was seen in all four patients with vasculitis or endarteritis obliterans, but this was also observed in 10 patients without vasculitis or endarteritis obliterans. None of the patients developed disseminated intravascular coagulation.

CONCLUSIONS

Our results suggest that diffuse cerebral intravascular coagulation is an additional explanation of cerebral infarction complicating pneumococcal meningitis.

Two centuries of meningococcal infection: from Vieusseux to the cellular and molecular basis of disease

Scientific knowledge of meningococcal infection has increased greatly since the epidemic nature of the illness was first described by Vieusseux at the dawn of the nineteenth century. In fact, revolutionary advances have been made in public-health measures, antimicrobial therapy, diagnostic procedures, anti-inflammatory drugs and supportive care facilities. Based on the knowledge accumulated to date, it is generally accepted that the pathogenesis of meningococcal infection involves multiple links that interconnect in a complex web of phenomena from Neisseria meningitidis attachment to meningococcal sepsis or meningitis. In fact, a myriad of strongly interacting inflammatory molecules and cells have been implicated in neisserial infection, illustrating the complexity of meningococcal pathogenesis. In addition, many of these signallers are critically involved in outcomes in the human host. Deciphering the pathogenesis of meningococcal infection could expand our knowledge and provide important clues to the host-pathogen interaction, as well as leading to the development of new therapeutic tools. Herein, we review the history of the discovery and characterization of meningococcal disease, epidemiological features of the disease with an emphasis on recent developments in Brazil, the cellular and molecular basis of disease, and discuss diagnosis and therapy.

Pediatric stroke: current developments

PURPOSE OF REVIEW

Pediatric arterial ischemic stroke is relatively rare but carries a considerable impact and high risk of recurrence--especially in patients with sickle cell disease and various forms of vasculopathy. We will discuss risk factors, vascular physiology, and primary/secondary/rehabilitative therapies. Goals for future investigation and treatment are suggested.

RECENT FINDINGS

Risk factors include chronic disease, vasculopathy, acute illness, cardiac disease, head and neck trauma, infection, and prothrombic disorders. Research has begun to implicate genetic risk factors--initially in sickle cell disease and more recently in prothrombotic disorders, moyamoya, and nitric oxide regulation. The vascular physiology of pediatric arterial ischemic stroke, especially sickle cell disease stroke, is currently undergoing study in animal models and in humans. No primary prevention therapy for pediatric arterial ischemic stroke is known. Various primary and secondary prevention therapies are used, however, in at-risk sickle cell disease patients. Aspirin, coumadin, and heparin are often initiated as secondary prevention therapies for non-sickle cell disease-associated arterial ischemic stroke, but no studies have assessed efficacy.

SUMMARY

Pediatric arterial ischemic stroke is under-recognized and under-studied. Investigation into the hemodynamic aspects of arterial ischemic stroke, although best studied thus far in sickle cell disease, has been neglected. It is likely that enhanced study of hemodynamics and autoregulation will elucidate both new prevention opportunities and novel treatments.