Genomic pneumococcal load and CSF cytokines are not related to outcome in Malawian adults with meningitis

Cerebrospinal fluid multiplex PCR cycle thresholds may predict ICU admission in community-acquired meningoencephalitis

OBJECTIVE

We investigated the relationship between cerebrospinal fluid (CSF) PCR cycle threshold (Ct) values, clinical characteristics, and outcomes in suspected CAM, while assessing QIAstat-Dx® ME Panel concordance with routine diagnostic methods.

METHODS

Frozen CSF from 30 individuals with suspected CAM were analyzed using the QIAstat-Dx® ME Panel. Ct values were categorized as low (≤ 30) or high (>30). Concordance with CSF FilmArray®/culture results was assessed using the Kappa coefficient.

RESULTS

Low Ct values were associated to CSF markers of meningitis and predicted ICU admissions (log-rank P = 0.025), particularly within the first two weeks of hospitalization (85 % for low Ct values versus 50 % for high Ct values, P = 0.041). Ct values were not associated with mortality in the survival analysis (log-rank P = 0.109). Substantial agreement was observed between QIAstat-Dx® and comparators (96.7 %, Kappa 0.839).

CONCLUSIONS

CSF Ct values can assist in risk stratification for timely ICU admission in individuals with CAM.

Understanding the mechanisms of Streptococcus pneumoniae in penetrating the blood-brain barrier: insights into bacterial binding with central nervous system host receptors

This review investigates the pathogenic processes through which Streptococcus pneumoniae crosses the blood-brain barrier (BBB) to cause meningitis, with a focus on the interaction with host receptors in the central nervous system (CNS). S. pneumoniae a primary cause of bacterial meningitis, utilizes unique receptor-mediated pathways to infiltrate the BBB. The bacterial interaction with the platelet-activating factor receptor (PAFR) and the polymeric immunoglobulin receptor (pIgR) is looked at in this study. The goal is to understand how this interaction helps the bacterium move across the BBB and cause infection in the CNS. We examine the functions of cellular and molecular participants at the endothelium level, such as cytokines, chemokines, and matrix metalloproteinases (MMP), which have a role in the development of the disease. This study consolidates data from multiple studies, providing a thorough summary of the interactions between S. pneumoniae and the BBB. It also explores potential treatment targets that could reduce the significant illness and death rates associated with pneumococcal meningitis.

Acute bacterial meningitis

Purpose of review

Community-acquired bacterial meningitis is a continually changing disease. This review summarises both dynamic epidemiology and emerging data on pathogenesis. Updated clinical guidelines are discussed, new agents undergoing clinical trials intended to reduce secondary brain damage are presented.

Recent findings

Conjugate vaccines are effective against serotype/serogroup-specific meningitis but vaccine escape variants are rising in prevalence. Meningitis occurs when bacteria evade mucosal and circulating immune responses and invade the brain: directly, or across the blood–brain barrier. Tissue damage is caused when host genetic susceptibility is exploited by bacterial virulence. The classical clinical triad of fever, neck stiffness and headache has poor diagnostic sensitivity, all guidelines reflect the necessity for a low index of suspicion and early Lumbar puncture. Unnecessary cranial imaging causes diagnostic delays. cerebrospinal fluid (CSF) culture and PCR are diagnostic, direct next-generation sequencing of CSF may revolutionise diagnostics. Administration of early antibiotics is essential to improve survival. Dexamethasone partially mitigates central nervous system inflammation in high-income settings. New agents in clinical trials include C5 inhibitors and daptomycin, data are expected in 2025.

Summary

Clinicians must remain vigilant for bacterial meningitis. Constantly changing epidemiology and emerging pathogenesis data are increasing the understanding of meningitis. Prospects for better treatments are forthcoming.

CSF Levels of Elongation Factor Tu Is Associated With Increased Mortality in Malawian Adults With Streptococcus pneumoniae Meningitis

Background

Mortality from bacterial meningitis, predominately caused by Streptococcus pneumoniae, exceeds 50% in sub-Saharan African countries with high HIV prevalence. Underlying causes of high mortality are poorly understood. We examined the host and pathogen proteome in the CSF of adults with proven pneumococcal meningitis (PM), testing if there was an association between differentially expressed proteins and outcome.

Materials/Methods

CSF proteomes were analyzed by quantitative Mass-Spectrometry. Spectra were identified using the Swissprot human and TIGR4 pneumococcal protein libraries. Proteins were quantitated and analyzed against mortality. Unique proteins in PM were identified against published normal CSF proteome. Random-Forest models were used to test for protein signatures discriminating outcome. Proteins of interest were tested for their effects on growth and neutrophil opsonophagocytic killing of S. pneumoniae.

Results

CSF proteomes were available for 57 Adults with PM (median age 32 years, 60% male, 70% HIV-1 co-infected, mortality 63%). Three hundred sixty individual human and 23 pneumococcal proteins were identified. Of the human protein hits, 30% were not expressed in normal CSF, and these were strongly associated with inflammation and primarily related to neutrophil activity. No human protein signature predicted outcome. However, expression of the essential S. pneumoniae protein Elongation Factor Tu (EF-Tu) was significantly increased in CSF of non-survivors [False Discovery Rate (q) <0.001]. Expression of EF-Tu was negatively co-correlated against expression of Neutrophil defensin (r 0.4 p p < 0.002), but not against complement proteins C3 or Factor H. In vitro, addition of EF-Tu protein impaired S. pneumoniae neutrophil killing in CSF.

Conclusions

Excessive S. pneumoniae EF-Tu protein in CSF was associated with reduced survival in meningitis in a high HIV prevalence population. We show EF-Tu may inhibit neutrophil mediated killing of S. pneumoniae in CSF. Further mechanistic work is required to better understand how S. pneumoniae avoids essential innate immune responses during PM through production of excess EF-Tu.

Molecular studies of meningococcal and pneumococcal meningitis patients in Ethiopia

Neisseria meningitidis infections in sub-Saharan Africa usually present with distinct symptoms of meningitis but very rarely as fulminant septicemia when reaching hospitals. In Europe, development of persistent meningococcal shock and multiple organ failure occurs in up to 30% of patients and is associated with a bacterial load of >106/ml plasma or serum. We have prospectively studied 27 Ethiopian patients with meningococcal infection as diagnosed and quantified with real-time PCR in the cerebrospinal fluid (CSF) and serum. All presented with symptoms of meningitis and none with fulminant septicemia. The median N. meningitidis copy number (NmDNA) in serum was < 3.5 × 103/ml, never exceeded 1.8 × 105/ml, and was always 10-1000 times higher in CSF than in serum. The levels of LPS in CSF as determined by the limulus amebocyte lysate assay were positively correlated to NmDNA copy number ( r = 0.45, P = 0.030), levels of IL-1 receptor antagonist, ( r = 0.46, P = 0.017), and matrix metallopeptidase-9 (MMP-9; r = 0.009). We also compared the inflammatory profiles of 19 mediators in CSF of the 26 meningococcal patients (2 died and 2 had immediate severe sequelae) with 16 patients with Streptococcus pneumoniae meningitis (3 died and 3 with immediate severe sequelae). Of 19 inflammatory mediators tested, 9 were significantly higher in patients with pneumococcal meningitis and possibly linked to worse outcome.

Blood‒Brain Barrier Pathology and CNS Outcomes in Streptococcus pneumoniae Meningitis

Streptococcus pneumoniae is a major meningitis-causing pathogen globally, bringing about significant morbidity and mortality, as well as long-term neurological sequelae in almost half of the survivors. Subsequent to nasopharyngeal colonisation and systemic invasion, translocation across the blood‒brain barrier (BBB) by S. pneumoniae is a crucial early step in the pathogenesis of meningitis. The BBB, which normally protects the central nervous system (CNS) from deleterious molecules within the circulation, becomes dysfunctional in S. pneumoniae invasion due to the effects of pneumococcal toxins and a heightened host inflammatory environment of cytokines, chemokines and reactive oxygen species intracranially. The bacteria‒host interplay within the CNS likely determines not only the degree of BBB pathological changes, but also host survival and the extent of neurological damage. This review explores the relationship between S. pneumoniae bacteria and the host inflammatory response, with an emphasis on the BBB and its roles in CNS protection, as well as both the acute and long-term pathogenesis of meningitis.

Cerebrospinal Fluid Cathelicidin Correlates With the Bacterial Load and Outcomes in Childhood Bacterial Meningitis

BACKGROUND

Large cerebrospinal fluid (CSF) bacterial load in bacterial meningitis (BM) relates to poor outcome. However, the antimicrobial peptide cathelicidin seems important to host defense. We studied how cathelicidin concentrations and bacterial load in CSF relate in childhood BM and to what extent they may predict the disease outcome.

METHODS

The patient data originated from a large prospective clinical trial in Latin America in 1996-2003 in which the CSF samples were collected on admission (CSF1) and 12-24 hours later (CSF2). The cathelicidin concentrations were measured by enzyme-linked immunosorbent assay and the CSF bacterial load by real-time polymerase chain reaction. This analysis comprised 76 children with meningitis caused by Haemophilus influenzae type b (n = 44), Streptococcus pneumoniae (n = 28) or Neisseria meningitidis (n = 4).

RESULTS

The cathelicidin concentration correlated with the bacterial genome count in both samples (CSF1: ρ = 0.531, P < 0.001; CSF2: ρ = 0.553, P < 0.001). A high CSF1 ratio of cathelicidin to the bacterial genome count was associated with fewer audiologic sequelae (odds ratio: 0.11, 95% confidence interval: 0.02-0.61, P = 0.01) and more favorable neurologic outcomes (odds ratio: 3.95, 95% confidence interval: 1.22-12.8, P = 0.02), but not with better survival.

CONCLUSIONS

In conclusion, CSF cathelicidin and the bacterial load were closely related in childhood BM. A high initial cathelicidin-to-bacterial genome count ratio predicted better outcomes in survivors.

Goal directed therapy for suspected acute bacterial meningitis in adults and adolescents in sub-Saharan Africa

Background

Mortality from acute bacterial meningitis (ABM) in sub-Saharan African adults and adolescents exceeds 50%. We tested if Goal Directed Therapy (GDT) was feasible for adults and adolescents with clinically suspected ABM in Malawi.

Materials and methods

Sequential patient cohorts of adults and adolescents with clinically suspected ABM were recruited in the emergency department of a teaching hospital in Malawi using a before/after design. Routine care was monitored in year one (P1). In year two (P2), nurses delivered protocolised GDT (rapid antibiotics, airway support, oxygenation, seizure control and fluid resuscitation) to a second cohort. The primary endpoint was composite mean number of clinical goals attained. Secondary endpoints were individual goals attained and death or disability from proven or probable ABM at day 40.

Results

563 patients with suspected ABM were enrolled in the study; 273 were monitored in P1; 290 patients with suspected ABM received GDT in P2. 61% were male, median age 33 years and 90% were HIV co-infected. ABM was proven or probable in 132 (23%) patients. GDT attained more clinical goals compared to routine care: composite mean number of goals in P1 was 0·55 vs. 1·57 in P2 GDT (p<0·001); Death or disability by day 40 from proven or probable ABM occurred in 29/57 (51%) in P1 and 38/60 (63%) in P2 (p = 0·19).

Conclusion

Nurse-led GDT in a resource-constrained setting was associated with improved delivery of protocolised care. Outcome was unaffected.

Trial registration

www.isrctn.comISRCTN96218197

Patterns of Local and Systemic Cytokines in Bacterial Meningitis and its Relation with Severity and Long-Term Sequelae

Bacterial meningitis (BM) is a pyogenic infection present in the subarachnoid space, potentially fatal and frequently associated with neurological sequelae. During BM, cytokines (CTs) are locally produced. We sought to determine the CTs' clinical role as disease severity predictors in adults, which is not completely clear. Using a bead-based flow cytometric assay, levels of six CTs were determined in cerebrospinal fluid (CSF) and plasma from 18 adult BM patients and 19 uninfected controls. Long-term neurological sequelae were evaluated using the Glasgow Outcome Scale (GOS). All evaluated CTs were higher in CSF than in plasma, and the levels of CSF interleukin (IL)-6, IL-8, IL-10, IL-1β, and tumor necrosis factor-α and plasma IL-10 and IL-12p70 were significantly higher in patients with severe sepsis than with sepsis, suggesting an association with clinical severity. There was a strong negative correlation between CSF IL-6 and plasma IL-12p70 with GOS score, supporting the possible role of these CTs in the development of neurological long-term sequelae. These findings could be helpful to identify candidates to receive neuroprotective treatments and early physiotherapy schemes.