Pneumolysin promotes host cell necroptosis and bacterial competence during pneumococcal meningitis as shown by whole-animal dual RNA-seq

Pneumolysin is a major virulence factor of Streptococcus pneumoniae that plays a key role in interaction with the host during invasive disease. How pneumolysin influences these dynamics between host and pathogen interaction during early phase of central nervous system infection in pneumococcal meningitis remains unclear. Using a whole-animal in vivo dual RNA sequencing (RNA-seq) approach, we identify pneumolysin-specific transcriptional responses in both S. pneumoniae and zebrafish (Danio rerio) during early pneumococcal meningitis. By functional enrichment analysis, we identify host pathways known to be activated by pneumolysin and discover the importance of necroptosis for host survival. Inhibition of this pathway using the drug GSK'872 increases host mortality during pneumococcal meningitis. On the pathogen's side, we show that pneumolysin-dependent competence activation is crucial for intra-host replication and virulence. Altogether, this study provides new insights into pneumolysin-specific transcriptional responses and identifies key pathways involved in pneumococcal meningitis.

Joint sequencing of human and pathogen genomes reveals the genetics of pneumococcal meningitis

Streptococcus pneumoniae is a common nasopharyngeal colonizer, but can also cause life-threatening invasive diseases such as empyema, bacteremia and meningitis. Genetic variation of host and pathogen is known to play a role in invasive pneumococcal disease, though to what extent is unknown. In a genome-wide association study of human and pathogen we show that human variation explains almost half of variation in susceptibility to pneumococcal meningitis and one-third of variation in severity, identifying variants in CCDC33 associated with susceptibility. Pneumococcal genetic variation explains a large amount of invasive potential (70%), but has no effect on severity. Serotype alone is insufficient to explain invasiveness, suggesting other pneumococcal factors are involved in progression to invasive disease. We identify pneumococcal genes involved in invasiveness including pspC and zmpD, and perform a human-bacteria interaction analysis. These genes are potential candidates for the development of more broadly-acting pneumococcal vaccines.

Association between TLR2 + 2477G/A polymorphism and bacterial meningitis: a meta-analysis

Toll-like receptor 2 (TLR2) is a key member of TLRs, which is crucial in the initial inflammatory response against bacteria. TLR2, is also the initial barrier against bacterial infection and plays an important role in recognising a variety of bacterial lipoproteins. Several studies have been performed to investigate the TLR2 + 2477G/A polymorphism and bacterial meningitis susceptibility. Unfortunately, the results of previous studies were controversial. Therefore, we performed a meta-analysis to derive a more precise estimation of the association. The association between the TLR2 + 2477G/A polymorphism and bacterial meningitis susceptibility was assessed by odds ratios together with their 95% confidence intervals (CI). Six studies were enrolled in the present meta-analysis. Overall, no significant association between TLR2 + 2477G/A polymorphism and bacterial meningitis risk were found under allele contrast (A vs. G: OR = 1.15, 95% CI = 0.93-1.43, P = 0.202), recessive genetic model (AA vs. AG/GG: OR = 1.12, 95% CI = 0.90-1.41, P = 0.313). The significant association was found between TLR2 + 2477G/A polymorphism and pneumococcal meningitis risk under allele contrast (A vs. G: OR = 1.54, 95% CI = 1.01-2.36, P = 0.046), recessive genetic model (AA vs. AG/GG: OR = 1.63, 95% CI = 1.03-2.57, P = 0.035). We conclude that TLR2 + 2477G/A polymorphism is not associated with meningococcal meningitis risk but contributes an increased risk of pneumococcal meningitis.

Mannose-binding lectin-deficient genotypes as a risk factor of pneumococcal meningitis in infants

Objectives

The objective of this study was to evaluate to evaluate the role of mannose-binding-lectin deficient genotypes in pneumococcal meningitis (PM) in children.

Methods

We performed a 16-year retrospective study (January 2001 to March 2016) including patients ≤ 18 years with PM. Variables including attack rate of pneumococcal serotype (high or low invasive capacity) and MBL2 genotypes associated with low serum MBL levels were recorded.

Results

Forty-eight patients were included in the study. Median age was 18.5 months and 17/48 episodes (35.4%) occurred in children ≤ 12 months old. Serotypes with high-invasive disease potential were identified in 15/48 episodes (31.2%). MBL2 deficient genotypes accounted for 18.8% (9/48). Children ≤ 12 months old had a 7-fold risk (95% CI: 1.6–29.9; p < 0.01) of having a MBL2 deficient genotype in comparison to those > 12 months old. A sub-analysis of patients by age group revealed significant proportions of carriers of MBL2 deficient genotypes among those ≤ 12 months old with PM caused by opportunistic serotypes (54.5%), admitted to the PICU (Pediatric Intensive Care Unit) (46.7%) and of White ethnicity (35.7%). These proportions were significantly higher than in older children (all p<0.05).

Conclusions

Our results suggest that differences in MBL2 genotype in children ≤12 months old affects susceptibility to PM, and it may have an important role in the episodes caused by non-high invasive disease potential serotypes.

Infection of zebrafish embryos with live fluorescent Streptococcus pneumoniae as a real-time pneumococcal meningitis model

BACKGROUND

Streptococcus pneumoniae is one of the most important causes of bacterial meningitis, an infection where unfavourable outcome is driven by bacterial and host-derived toxins. In this study, we developed and characterized a pneumococcal meningitis model in zebrafish embryos that allows for real-time investigation of early host-microbe interaction.

METHODS

Zebrafish embryos were infected in the caudal vein or hindbrain ventricle with green fluorescent wild-type S. pneumoniae D39 or a pneumolysin-deficient mutant. The kdrl:mCherry transgenic zebrafish line was used to visualize the blood vessels, whereas phagocytic cells were visualized by staining with far red anti-L-plastin or in mpx:GFP/mpeg1:mCherry zebrafish, that have green fluorescent neutrophils and red fluorescent macrophages. Imaging was performed by fluorescence confocal and time-lapse microscopy.

RESULTS

After infection by caudal vein, we saw focal clogging of the pneumococci in the blood vessels and migration of bacteria through the blood-brain barrier into the subarachnoid space and brain tissue. Infection with pneumolysin-deficient S. pneumoniae in the hindbrain ventricle showed attenuated growth and migration through the brain as compared to the wild-type strain. Time-lapse and confocal imaging revealed that the initial innate immune response to S. pneumoniae in the subarachnoid space mainly consisted of neutrophils and that pneumolysin-mediated cytolytic activity caused a marked reduction of phagocytes.

CONCLUSIONS

This new meningitis model permits detailed analysis and visualization of host-microbe interaction in pneumococcal meningitis in real time and is a very promising tool to further our insights in the pathogenesis of pneumococcal meningitis.

Thrombin-activatable fibrinolysis inhibitor influences disease severity in humans and mice with pneumococcal meningitis

BACKGROUND

Mortality and morbidity in patients with bacterial meningitis result from the proinflammatory response and dysregulation of coagulation and fibrinolysis. Thrombin-activatable fibrinolysis inhibitor (TAFI) is activated by free thrombin or thrombin in complex with thrombomodulin, and plays an antifibrinolytic role during fibrin clot degradation, but also has an anti-inflammatory role by inactivating proinflammatory mediators, such as complement activation products.

OBJECTIVE

To assess the role of TAFI in pneumococcal meningitis.

METHODS

We performed a prospective nationwide genetic association study in patients with bacterial meningitis, determined TAFI and complement levels in cerebrospinal fluid (CSF), and assessed the function of TAFI in a pneumococcal meningitis mouse model by using Cpb2 (TAFI) knockout mice.

RESULTS

Polymorphisms (reference sequences: rs1926447 and rs3742264) in the CPB2 gene, coding for TAFI, were related to the development of systemic complications in patients with pneumococcal meningitis. Higher protein levels of TAFI in CSF were significantly associated with CSF complement levels (C3a, iC3b, and C5b-9) and with more systemic complications in patients with bacterial meningitis. The risk allele of rs1926447 (TT) was associated with higher levels of TAFI in CSF. In the murine model, consistent with the human data, Cpb2-deficient mice had decreased disease severity, as reflected by lower mortality, and attenuated cytokine levels and bacterial outgrowth in the systemic compartment during disease, without differences in the brain compartment, as compared with wild-type mice.

CONCLUSIONS

These findings suggest that TAFI plays an important role during pneumococcal meningitis, which is likely to be mediated through inhibition of the complement system, and influences the occurrence of systemic complications and inflammation.

[Real-time pcr procedure for determination of Streptococcus pneumoniae serotypes]

AIM

Development and application of real-time PCR (RT-PCR) procedure for determination of Streptococcus pneumoniae serotypes.

MATERIALS AND METHODS

S. pneumoniae cps-locus wzx, wzy, wzz, wcwV and galU genes were chosen as PCR targets to select serotype-specific oligonucleotide primers and fluorescent labeled probes. 89 samples of cerebrospinal fluid (CSF) obtained in 2007 - 2010 from patients with pneumococcal meningitis diagnosis undergoing therapy in the Infectious Clinical Hospital No. 2, Moscow, were studied with the aim of testing the possibility of practical use of RT-PCR.

RESULTS

Primers and probes were selected for the determination of 16 vaccine and/or frequently encountered serotypes distributed among 4 reaction mixtures also including a pair of primers and a probe for cpsA gene detection that is present in all the capsule pneumococci (internal control). The procedure was tested on a collection of 108 pneumococci strains gathered in Research Institute of Antimicrobial Therapy and serotyped earlier by specific PCR with electrophoretic detection and serologically by using Pneumotest-Latex kit. The sensitivity and specificity of the RT-PCR was 100%. RT-PCR procedure allowed to determine pneumococcus serotype in 79% of CSF clinical samples containing S. pneumoniae DNA. Serotype 3 and 23F were detected most frequently (13%, each).

CONCLUSION

RT-PCR application does not assume causative agent seeding stage, significantly reduces analysis execution time and increases sensitivity of the study. The developed procedure will allow to begin addressing the important problem--clarification of spectra and frequency of occurrence of pneumococci serotypes circulating on the territory of Russia.

Bacterial cytolysin during meningitis disrupts the regulation of glutamate in the brain, leading to synaptic damage

Streptococcus pneumoniae (pneumococcal) meningitis is a common bacterial infection of the brain. The cholesterol-dependent cytolysin pneumolysin represents a key factor, determining the neuropathogenic potential of the pneumococci. Here, we demonstrate selective synaptic loss within the superficial layers of the frontal neocortex of post-mortem brain samples from individuals with pneumococcal meningitis. A similar effect was observed in mice with pneumococcal meningitis only when the bacteria expressed the pore-forming cholesterol-dependent cytolysin pneumolysin. Exposure of acute mouse brain slices to only pore-competent pneumolysin at disease-relevant, non-lytic concentrations caused permanent dendritic swelling, dendritic spine elimination and synaptic loss. The NMDA glutamate receptor antagonists MK801 and D-AP5 reduced this pathology. Pneumolysin increased glutamate levels within the mouse brain slices. In mouse astrocytes, pneumolysin initiated the release of glutamate in a calcium-dependent manner. We propose that pneumolysin plays a significant synapto- and dendritotoxic role in pneumococcal meningitis by initiating glutamate release from astrocytes, leading to subsequent glutamate-dependent synaptic damage. We outline for the first time the occurrence of synaptic pathology in pneumococcal meningitis and demonstrate that a bacterial cytolysin can dysregulate the control of glutamate in the brain, inducing excitotoxic damage.

Bacterial meningitis is one of the most devastating brain diseases. Among the bacteria that cause meningitis, Streptococcus pneumoniae is the most common. Meningitis predominantly affects children, especially in the Third World, and most of them do not survive. Those that do survive often suffer permanent brain damage and hearing problems. The exact morphological substrates of brain damage in Streptococcus pneumoniae meningitis remain largely unknown. In our experiments, we found that the brain cortex of patients with meningitis demonstrated a loss of synapses (the contact points among neurons, responsible for the processes of learning and memory), and we identified the major pneumococcal neurotoxin pneumolysin as a sufficient cause of this loss. The effect was not direct but was mediated by the brain neurotransmitter glutamate, which was released upon toxin binding by one of the non-neuronal cell types of the brain – the astrocytes. Pneumolysin initiated calcium influx in astrocytes and subsequent glutamate release. Glutamate damaged the synapses via NMDA-receptors – a mechanism similar to the damage occurring in brain ischemia. Thus, we show that synaptic loss is present in pneumococcal meningitis, and we identify the toxic bacterial protein pneumolysin as the major factor in this process. These findings alter our understanding of bacterial meningitis and establish new therapeutic strategies for this fatal disease.

Genetic variation in the β2-adrenocepter gene is associated with susceptibility to bacterial meningitis in adults

Recently, the biased β2-adrenoceptor/β-arrestin pathway was shown to play a pivotal role in crossing of the blood brain barrier by Neisseria meningitidis. We hypothesized that genetic variation in the β2-adrenoceptor gene (ADRB2) may influence susceptibility to bacterial meningitis. In a prospective genetic association study we genotyped 542 patients with CSF culture proven community acquired bacterial meningitis and 376 matched controls for 2 functional single nucleotide polymorphisms in the β2-adrenoceptor gene (ADRB2). Furthermore, we analyzed if the use of non-selective beta-blockers, which bind to the β2-adrenoceptor, influenced the risk of bacterial meningitis. We identified a functional polymorphism in ADRB2 (rs1042714) to be associated with an increased risk for bacterial meningitis (Odds ratio [OR] 1.35, 95% confidence interval [CI] 1.04–1.76; p = 0.026). The association remained significant after correction for age and was more prominent in patients with pneumococcal meningitis (OR 1.52, 95% CI 1.12–2.07; p = 0.007). For meningococcal meningitis the difference in genotype frequencies between patients and controls was similar to that in pneumococcal meningitis, but this was not statistically significant (OR 1.43, 95% CI 0.60–3.38; p = 0.72). Patients with bacterial meningitis had a lower frequency of non-selective beta-blockers use compared to the age matched population (0.9% vs. 1.8%), although this did not reach statistical significance (OR 1.96 [95% CI 0.88–4.39]; p = 0.09). In conclusion, we identified an association between a genetic variant in the β2-adrenoceptor and increased susceptibility to bacterial meningitis. The potential benefit of pharmacological treatment targeting the β2-adrenoceptor to prevent bacterial meningitis in the general population or patients with bacteraemia should be further studied in both experimental studies and observational cohorts.

Serial PCR genetic load determination in the surgical management of pneumococcal intracranial sepsis

PURPOSE

Aspirated intracranial fluid, in the surgical management of intracranial sepsis, may not culture an organism due to the previous administration of antibiotics. We have sought to utilise polymerase chain reaction (PCR) to determine the cause of culture-negative sepsis and in monitoring response to therapy.

METHODS

This was a retrospective review of five cases of Streptococcus pneumoniae intracranial sepsis. Samples were analysed using real-time quantitative PCR targeting the pneumococcal lytA gene and the number of genome copies per microlitre of sample determined.

RESULTS

Streptococcus pneumoniae sepsis was diagnosed by PCR in five culture-negative cases comprising: ventriculitis (×3), subdural empyema and meningitis. Serial serum inflammatory markers (CRP and WBC) and number of genome copies were graphically plotted over the duration of inpatient stay for cases requiring surgical drainage of recurrent collections or external ventricular drainage. A correlation was demonstrated between change in bacterial genomic load and serum inflammatory markers, reflecting similar changes in clinical state.

CONCLUSIONS

This is the first report of the use of serial quantitative PCR in monitoring the course of intracranial sepsis secondary to S. pneumoniae. Further work is required to determine the precise relationship between serum inflammatory markers, clinical state and bacterial load: do changes in one precede the other? Furthermore, a threshold value for number of genome copies in cerebrospinal fluid/aspirate samples has yet to be defined.

Adjunctive dexamethasone affects the expression of genes related to inflammation, neurogenesis and apoptosis in infant rat pneumococcal meningitis

Streptococcus pneumoniae is the most common pathogen causing non-epidemic bacterial meningitis worldwide. The immune response and inflammatory processes contribute to the pathophysiology. Hence, the anti-inflammatory dexamethasone is advocated as adjuvant treatment although its clinical efficacy remains a question at issue. In experimental models of pneumococcal meningitis, dexamethasone increased neuronal damage in the dentate gyrus. Here, we investigated expressional changes in the hippocampus and cortex at 72 h after infection when dexamethasone was given to infant rats with pneumococcal meningitis. Nursing Wistar rats were intracisternally infected with Streptococcus pneumoniae to induce experimental meningitis or were sham-infected with pyrogen-free saline. Besides antibiotics, animals were either treated with dexamethasone or saline. Expressional changes were assessed by the use of GeneChip® Rat Exon 1.0 ST Arrays and quantitative real-time PCR. Protein levels of brain-derived neurotrophic factor, cytokines and chemokines were evaluated in immunoassays using Luminex xMAP® technology. In infected animals, 213 and 264 genes were significantly regulated by dexamethasone in the hippocampus and cortex respectively. Separately for the cortex and the hippocampus, Gene Ontology analysis identified clusters of biological processes which were assigned to the predefined categories "inflammation", "growth", "apoptosis" and others. Dexamethasone affected the expression of genes and protein levels of chemokines reflecting diminished activation of microglia. Dexamethasone-induced changes of genes related to apoptosis suggest the downregulation of the Akt-survival pathway and the induction of caspase-independent apoptosis. Signalling of pro-neurogenic pathways such as transforming growth factor pathway was reduced by dexamethasone resulting in a lack of pro-survival triggers. The anti-inflammatory properties of dexamethasone were observed on gene and protein level in experimental pneumococcal meningitis. Further dexamethasone-induced expressional changes reflect an increase of pro-apoptotic signals and a decrease of pro-neurogenic processes. The findings may help to identify potential mechanisms leading to apoptosis by dexamethasone in experimental pneumococcal meningitis.

Identification of serotype in culture negative pneumococcal meningitis using sequential multiplex PCR: implication for surveillance and vaccine design

Background

PCR-based serotyping of Streptococcus pneumoniae has been proposed as a simpler approach than conventional methods, but has not been applied to strains in Asia where serotypes are diverse and different from other part of the world. Furthermore, PCR has not been used to determine serotype distribution in culture-negative meningitis cases.

Methodology

Thirty six serotype-specific primers, 7 newly designed and 29 previously published, were arranged in 7 multiplex PCR sets, each in new hierarchies designed for overall serotype distribution in Bangladesh, and specifically for meningitis and non-meningitis isolates. Culture-negative CSF specimens were then tested directly for serotype-specific sequences using the meningitis-specific set of primers. PCR-based serotyping of 367 strains of 56 known serotypes showed 100% concordance with quellung reaction test. The first 7 multiplex reactions revealed the serotype of 40% of all, and 31% and 48% non-meningitis and meningitis isolates, respectively. By redesigning the multiplex scheme specifically for non-meningitis or meningitis, the quellung reaction of 43% and 48% of respective isolates could be identified. Direct examination of 127 culture-negative CSF specimens, using the meningitis-specific set of primers, yielded serotype for 51 additional cases.

Conclusions

This PCR approach, could improve ascertainment of pneumococcal serotype distributions, especially for meningitis in settings with high prior use of antibiotics.

Gene and protein expression of galectin-3 and galectin-9 in experimental pneumococcal meningitis

Inflammation of the subarachnoid and ventricular space contributes to the development of brain damage i.e. cortical necrosis and hippocampal apoptosis in pneumococcal meningitis (PM). Galectin-3 and -9 are known pro-inflammatory mediators and regulators of apoptosis. Here, the gene and protein expression profile for both galectins was assessed in the disease progression of PM. The mRNA of Lgals3 and Lgals9 increased continuously in the cortex and in the hippocampus from 22 h to 44 h after infection. At 44 h after infection, mRNA levels of Lgals9 in the hippocampus were 7-fold and those of Lgals3 were 30-fold higher than in uninfected controls (P<0.01). Galectin-9 protein did not change, but galectin-3 significantly increased in cortex and hippocampus with the duration of PM. Galectin-3 was localized to polymorphonuclear neutrophils, microglia, monocytes and macrophages, suggesting an involvement of galectin-3 in the neuroinflammatory processes leading to brain damage in PM.

TGFbeta receptor II gene deletion in leucocytes prevents cerebral vasculitis in bacterial meningitis

In bacterial meningitis, chemokines lead to recruitment of polymorphonuclear leucocytes (PMN) into the CNS. At the site of infection in the subarachnoid space, PMN release reactive oxygen species, reactive nitrogen intermediates (RNI) and interleukin-1beta (IL-1beta). Although these immune factors assist in clearance of bacteria, they also result in neuronal injury associated with meningitis. Transforming growth factor beta (TGFbeta) is a potent deactivator of PMN and macrophages since TGFbeta suppresses the production of ROI, RNI and IL-1. Here, we report that the deletion of the TGFbeta receptor II gene in PMN enhances PMN recruitment into the CNS of mice with Streptococcus pneumoniae meningitis. This was associated with more efficient clearance of bacteria, and almost complete prevention of intracerebral necrotizing vasculitis. Differences in PMN in the CNS of infected control mice and mice lacking TGFbeta receptor II were not explained by altered expression of chemokines acting on PMN. Instead, TGFbeta was found to impair the expression of L (leucocyte)-selectin on PMN from control mice but not from mice lacking TGFbeta receptor II. L-selectin is known to be essential for PMN recruitment in bacterial meningitis. We conclude that defective TGFbeta signalling in PMN is beneficial in bacterial meningitis by ameliorating migration of PMN and bacterial clearance.

Gene expression in cortex and hippocampus during acute pneumococcal meningitis

Background

Pneumococcal meningitis is associated with high mortality (~30%) and morbidity. Up to 50% of survivors are affected by neurological sequelae due to a wide spectrum of brain injury mainly affecting the cortex and hippocampus. Despite this significant disease burden, the genetic program that regulates the host response leading to brain damage as a consequence of bacterial meningitis is largely unknown.

We used an infant rat model of pneumococcal meningitis to assess gene expression profiles in cortex and hippocampus at 22 and 44 hours after infection and in controls at 22 h after mock-infection with saline. To analyze the biological significance of the data generated by Affymetrix DNA microarrays, a bioinformatics pipeline was used combining (i) a literature-profiling algorithm to cluster genes based on the vocabulary of abstracts indexed in MEDLINE (NCBI) and (ii) the self-organizing map (SOM), a clustering technique based on covariance in gene expression kinetics.

Results

Among 598 genes differentially regulated (change factor ≥ 1.5; p ≤ 0.05), 77% were automatically assigned to one of 11 functional groups with 94% accuracy. SOM disclosed six patterns of expression kinetics. Genes associated with growth control/neuroplasticity, signal transduction, cell death/survival, cytoskeleton, and immunity were generally upregulated. In contrast, genes related to neurotransmission and lipid metabolism were transiently downregulated on the whole. The majority of the genes associated with ionic homeostasis, neurotransmission, signal transduction and lipid metabolism were differentially regulated specifically in the hippocampus. Of the cell death/survival genes found to be continuously upregulated only in hippocampus, the majority are pro-apoptotic, while those continuously upregulated only in cortex are anti-apoptotic.

Conclusion

Temporal and spatial analysis of gene expression in experimental pneumococcal meningitis identified potential targets for therapy.

Two siblings with lethal pneumococcal meningitis in a family with a mutation in Interleukin-1 receptor-associated kinase 4

We describe two siblings with one confirmed and one inferred homozygous base pair deletion in the gene for interleukin-1-related kinase 4 (IRAK-4) who died of pneumococcal meningitis at 2 and 14 months, respectively. Interleukin-1-related kinase 4 deficiency is a potentially lethal immunodeficiency characterized by a poor inflammatory response to pyogenic infections.

Antibiotic susceptibility in relation to penicillin-binding protein genes and serotype distribution of Streptococcus pneumoniae strains responsible for meningitis in Japan, 1999 to 2002

The antibiotic susceptibilities, genotypes of penicillin (PEN)-binding protein genes (pbp), and serotype distributions of Streptococcus pneumoniae isolates from meningitis patients were investigated by a nationwide surveillance group in Japan between 1999 and 2002. We analyzed 146 isolates from children (</=17 years old) and 73 from adults (>/=18 years old). Isolates with or without abnormal pbp1a, pbp2x, or pbp2b genes identified by PCR were classified into six genotype patterns and 90% MIC (MIC(90)) values for PEN: (i) strains with three normal genes (17.2% of isolates; MIC(90), 0.031 micro g/ml); (ii) strains with abnormal pbp2x (22.1%, 0.063 micro g/ml); (iii) strains with abnormal pbp2b (1.0%, 0.125 micro g/ml); (iv) strains with abnormal pbp2x and pbp2b (7.4%, 0.25 micro g/ml); (v) strains with abnormal pbp1a and pbp2x (12.7%, 0.25 micro g/ml); and (vi) strains with three abnormal PBP genes (39.7%, 4 micro g/ml), which are termed genotypic PEN-resistant S. pneumoniae (gPRSP). Panipenem, a carbapenem, showed an excellent MIC(90) (0.125 micro g/ml) against gPRSP, followed by meropenem and vancomycin (0.5 micro g/ml), cefotaxime and ceftriaxone (1 micro g/ml), and ampicillin (4 micro g/ml). Strains of gPRSP were significantly more prevalent in children (45.2%) than in adults (27.4%). The most frequent serotypes were 6B, 19F, 23F, 6A, and 14 in children and 23F, 22, 3, 10, 6B, and 19F in adults. Serotypes 6B, 6A, 19F, 23F, and 14 predominated among gPRSP. In children, 7- and 11-valent pneumococcal conjugate vaccines would cover 76.2 and 81.3% of isolates, respectively, although coverage would be lower in adults (43.9 and 56.0%, respectively). These findings suggest the need for early introduction of pneumococcal conjugate vaccines and continuous bacteriological surveillance for meningitis.

Increased mortality and spatial memory deficits in TNF-α-deficient mice in ceftriaxone-treated experimental pneumococcal meningitis

Tumor necrosis factor-alpha (TNF-alpha) is critically involved in inflammation and may participate in hippocampal injury in bacterial meningitis. In a mouse model of ceftriaxone-treated pneumococcal meningitis, spatial memory and motor performance of TNF-alpha-deficient (n = 57) and control mice (n = 55) were investigated. After infection, therapy was initiated with ceftriaxone (100 mg/kg twice daily for 5 days). Sixty-three percent TNF-alpha-deficient mice and 40% control animals died within 6 days (Fisher's exact test: P = 0.02). TNF-alpha-deficient mice surviving pneumococcal meningitis took substantially longer to reach the hidden platform than controls, and the distance of swim tracks was longer (P = 0.02). The swim speed in both groups was similar (P = 0.59). The proliferation of dentate granule cells was lower in TNF-alpha-deficient than in wild-type mice (P = 0.03). In pneumococcal meningitis, TNF-alpha deficiency caused increased mortality and stronger deficits in spatial memory possibly due to impaired neurogenesis.

Regulation of brain-derived neurotrophic factor (BDNF) expression following antibiotic treatment of experimental bacterial meningitis

Although more and more new potent antibiotics have been used, mortality and neurologic deficits still occur frequently following bacterial meningitis in children. In this article, the expression of brain-derived neurotrophic factor messenger ribonucleic acid (RNA) and its production in the brains of rats were investigated during the course of experimental bacterial meningitis and after treatment with an antibiotic plus dexamethasone. In the brains of Streptococcus pneumoniae-inoculated rats, brain-derived neurotrophic factor (BDNF) messenger RNA was obviously up-regulated after inoculation for 24 hours (P < .01) and then declined but was still greater than that in the brains of control rats after inoculation for 5 days (P < .05). The expression of brain-derived neurotrophic factor in the brains of infected rats treated by antibiotic was dose dependent, down-regulated, and almost undetectable (P < .01) but up-regulated after treatment with an antibiotic plus dexamethasone (P < .01). However, the expression of brain-derived neurotrophic factor messenger RNA did not change in control rats treated with an antibiotic. Brain-derived neurotrophic factor protein showed similar changes, except it declined to normal levels 5 days after inoculation. Brain-derived neurotrophic factor messenger RNA and its production were observed in some infiltrating inflammatory cells in the brain of infected rats. The results of our studies support the hypothesis that brain-derived neurotrophic factor might play a neuroprotective role in brain damage during bacterial meningitis, and the expression of brain-derived neurotrophic factor messenger RNA and its production might be inhibited after treatment with antibiotics. The findings suggest that both eradicating the bacterial pathogen with antibiotics and adjuvant administering of brain-derived neurotrophic factor might be more beneficial to prevent brain damage.

Pneumococcal septic shock is associated with the interleukin-10-1082 gene promoter polymorphism

Polymorphisms in the tumor necrosis factor and interleukin-10 genes, linked to cytokine inducibility, may influence the inflammatory response to infection. We studied the biallelic interleukin-10-1082 promoter, the tumor necrosis factor-alpha-308 promoter, and the lymphotoxin-alpha polymorphisms with regard to the development of septic shock in pneumococcal infection. Sixty-nine patients with pneumococcal disease (61 patients with community-acquired pneumonia, 5 patients with meningitis, and 3 patients with pneumonia and meningitis) and 50 age-matched control subjects were included. The polymorphisms were determined by the polymerase chain reaction. In patients with pneumococcal disease, the lipopolysaccharide-stimulated tumor necrosis factor and interleukin-10 release from whole blood were measured by ELISA. Sepsis severity was documented according to standard criteria. No significant genotypic differences were seen between patients and control subjects. Thirteen of 69 patients with pneumococcal disease developed septic shock. Interleukin-10 allele G homozygous patients had the highest risk for septic shock (odds ratio of 6.1; 95% confidence interval, 1.4-27.2; corrected p = 0.024). The stimulated interleukin-10 release was highest in interleukin-10 G homozygous patients (p = 0.04). In conclusion, interleukin-10 polymorphism, associated with high interleukin-10 inducibility, might influence the outcome of pneumococcal infection via induced immunosuppression and impaired bacterial clearance.

Differential regulation of Toll-like receptor mRNAs in experimental murine central nervous system infections

Toll-like receptors (TLR) play a key role in the recognition of microbial components. We investigated the differential regulation of TLR mRNA expression in bacterial and viral mouse models of central nervous system infection. Streptococcus pneumoniae meningitis led to an enhanced expression of TLR2, TLR4 and TLR9 mRNA. In Escherichia coli meningitis, TLR2, TLR4 and TLR7 mRNA expression was increased and Herpes simplex encephalitis caused a rise of TLR4 mRNA. In organotypic hippocampal cultures treatment with S. pneumoniae R6 led to increased expression of TLR2 and TLR3 mRNA. Our data provide evidence that regulation of TLR mRNA is not fully specific for the molecular patterns of the infectious pathogen. The TLR mRNA regulation observed probably represents a combination of specific response to the causative pathogen and non-specific activation of the innate immune system.

Interleukin-18 gene-deficient mice show enhanced defense and reduced inflammation during pneumococcal meningitis

To determine the role of endogenous interleukin-18 (IL-18) in pneumococcal meningitis, meningitis was induced in IL-18 gene-deficient (IL-18(-/-)) and wild-type (WT) mice by intranasal inoculation of Streptococcus pneumoniae with hyaluronidase. Induction of meningitis resulted in an upregulation of both pro- and mature IL-18 in brain tissue in WT mice. IL-18(-/-) and WT mice were equally susceptible to develop meningitis after intranasal infection, yet IL-18(-/-) mice showed a prolonged survival and a suppressed inflammatory response, as reflected by a less profound inflammatory infiltrate around the meninges and lower concentrations of cytokines and chemokines in brain tissue. These findings suggest that endogenous IL-18 contributes to a detrimental inflammatory response during pneumococcal meningitis and that elimination of IL-18 may improve the outcome of this disease.

IL-1 receptor type 1 gene-deficient mice demonstrate an impaired host defense against pneumococcal meningitis

The fatality rate associated with Streptococcus pneumoniae meningitis remains high despite adequate antibiotic treatment. IL-1 is an important proinflammatory cytokine, which is up-regulated in brain tissue after the induction of meningitis. To determine the role of IL-1 in pneumococcal meningitis we induced meningitis by intranasal inoculation with 8 x 10(4) CFU of S. pneumoniae and 180 U of hyaluronidase in IL-1R type I gene-deficient (IL-1R(-/-)) mice and wild-type mice. Meningitis resulted in elevated IL-1alpha and IL-1beta mRNA and protein levels in the brain. The absence of an intact IL-1 signal was associated with a higher susceptibility to develop meningitis. Furthermore, the lack of IL-1 impaired bacterial clearance, as reflected by an increased number of CFU in cerebrospinal fluid of IL-1R(-/-) mice. The characteristic pleocytosis of meningitis was not significantly altered in IL-1R(-/-) mice, but meningitis was associated with lower brain levels of cytokines. The mortality was significantly higher and earlier in the course of the disease in IL-1R(-/-) mice. These results demonstrate that endogenous IL-1 is required for an adequate host defense in pneumococcal meningitis.

Toll-like receptor 2 participates in mediation of immune response in experimental pneumococcal meningitis

Heterologous expression of Toll-like receptor (TLR)2 and CD14 in Chinese hamster ovary fibroblasts was reported to confer responsiveness to pneumococcal peptidoglycan. The present study characterized the role of TLR2 in the host immune response and clinical course of pneumococcal meningitis. Pneumococcal infection of mice caused a significant increase in brain TLR2 mRNA expression at both 4 and 24 h postchallenge. Mice with a targeted disruption of the TLR2 gene (TLR2-/-) showed a moderate increase in disease severity, as evidenced by an aggravation of meningitis-induced intracranial complications, a more pronounced reduction in body weight and temperature, and a deterioration of motor impairment. These symptoms were associated with significantly higher cerebellar and blood bacterial titers. Brain expression of the complement inhibitor complement receptor-related protein y was significantly higher in infected TLR2-/- than in wild-type mice, while the expression of the meningitis-relevant inflammatory mediators IL-1beta, TNF-alpha, IL-6, macrophage-inflammatory protein (MIP)-2, inducible NO synthase, and C3 was similar in both genotypes. We first ectopically expressed single candidate receptors in HEK293 cells and then applied peritoneal macrophages from mice lacking TLR2 and/or functional TLR4 for further analysis. Overexpression of TLR2 and TLR4/MD-2 conferred activation of NF-kappaB in response to pneumococcal exposure. However, pneumococci-induced TNF-alpha release from peritoneal macrophages of wild-type and TLR2/functional TLR4/double-deficient mice did not differ. Thus, while TLR2 plays a significant role in vivo, yet undefined pattern recognition receptors contribute to the recognition of and initiation of the host immune defense toward Streptococcus pneumoniae infection.

A novel, multiple drug-resistant, serotype 24F strain of Streptococcus pneumoniae that caused meningitis in patients in Naples, Italy

Three adult patients in Naples, Italy, had meningitis due to multiple drug-resistant serotype 24F Streptococcus pneumoniae isolates. The 3 isolates were genetically indistinguishable and shared pbp2b and pspA sequence types with previously characterized penicillin-resistant clones. This serotype 24F strain was found to be the same clonal type as a previously characterized, penicillin-resistant serotype 14 strain. The novel strain has probably arisen through transformation of a serotype 14 strain with type 24F capsular biosynthetic operon sequences.

Differential Expression of Nitric Oxide Synthases in Bacterial Meningitis: Role of the Inducible Isoform for Blood‐Brain Barrier Breakdown

The aim of the study was to determine the differential expression of nitric oxide (NO) synthase (NOS) isoforms and the pathophysiologic relevance of inducible NOS (iNOS) in experimental pneumococcal meningitis. By use of reverse transcription-polymerase chain reaction analysis, immunohistochemistry, and Western blotting, increased brain mRNA and increased protein levels of endothelial NOS (eNOS) and iNOS were detected 24 h after intracisternal pneumococcal inoculation. In iNOS-deficient mice, disruption of the blood-brain barrier (BBB) was significantly reduced, compared with that in wild-type mice. This beneficial effect of iNOS deficiency was associated with a lack of nitrotyrosine immunoreactivity. Furthermore, brain protein levels of interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha and brain mRNA levels of macrophage inflammatory protein (MIP)-1alpha and MIP-2 were significantly reduced in infected animals lacking iNOS. These findings suggest that (1) not only iNOS but also eNOS is up-regulated in the acute phase of experimental bacterial meningitis, and (2) iNOS-derived NO contributes to peroxynitrite formation and BBB breaching in this disease.

The differential roles of LFA-1 and Mac-1 in host defense against systemic infection with Streptococcus pneumoniae

Mice deficient in CD18, which lack all four CD11 integrins, have leukocytosis and increased susceptibility to bacterial infection. To determine the effect of deficiencies in LFA-1 (CD11a/CD18) or Mac-1 (CD11b/CD18) on host defense against systemic bacterial infection, knockout mice were inoculated i.p. with Streptococcus pneumoniae. Increased mortality occurred in both LFA-1(-/-) (15 of 17 vs 13 of 35 in wild type (WT), p < 0.01) and Mac-1(-/-) (17 of 34 vs 6 of 25, p < 0.01) mice. All deaths in LFA-1(-/-) mice occurred after 72 h, whereas most deaths in Mac-1(-/-) mice occurred within 24-48 h. At 24 h, 21 of 27 Mac-1(-/-) mice were bacteremic, vs 15 of 25 WT (p = 0.05); no difference was observed between LFA-1(-/-) and WT. Increased bacteria were recovered from Mac-1(-/-) spleens at 2 h (p = 0.03) and 6 h (p = 0.002) and from livers (p = 0.001) by 6 h. No difference was observed at 2 h in LFA-1(-/-) mice, but by 6 h increased bacteria were recovered from spleens (p = 0.008) and livers (p = 0.04). Baseline and peak leukocyte counts were similar between Mac-1(-/-) and WT, but elevated in LFA-1(-/-). At 8 h, peritoneal neutrophils were increased in Mac-1(-/-), but not significantly different in LFA-1(-/-). Histopathologically, at 24 h Mac-1(-/-) animals had bacteremia and lymphoid depletion, consistent with sepsis. LFA-1(-/-) mice had increased incidence of otitis media and meningitis/encephalitis vs WT at 72 and 96 h. Both Mac-1 and LFA-1 play important but distinct roles in host defense to S. pneumoniae.

A polymerase chain reaction-enzyme immunoassay for diagnosis of pneumococcal meningitis in children and adults

BACKGROUND AND OBJECTIVES

meningitis due to Streptococcus pneumoniae is common among children and adults. In this study a polymerase chain reaction (PCR) for diagnosis of pneumococcal meningitis was evaluated prospectively.

METHODS

a total of 61 cerebrospinal fluid specimens were included prospectively using defined inclusion and exclusion criteria. These samples were studied by PCR-EIA and results compared with conventional microbiological procedures and antigen detection techniques. Primers were used against the conserved region of the pneumococcal autolysin gene and the amplified product was labelled using the digoxigenin-labelled dUTP. The product was detected by an enzyme immuno assay (EIA) after hybridization with a biotin labelled probe.

RESULTS

a total of 15 specimens were positive for S.pneumoniae by one or more methods used. Culture for S.pneumoniae was positive in 13 specimens, PCR-EIA was positive in 11 of these specimens with an additional pickup of 2 specimens and latex agglutination (LA) positive only in one.

INTERPRETATION AND CONCLUSIONS

sensitivity and specificity of 84.6 and 95.8 per cent respectively were observed with PCR-EIA. It seems to be a good tool for the diagnosis of pneumococcal meningitis especially in cases of partially treated pyogenic meningitis.

[Pneumococcal meningitis resistant to penicillin and nosocomial transmission in pediatric hospitals confirmed by genomic analysis]

BACKGROUND

Careful epidemiological studies and sophisticated diagnostic procedures are necessary to prove that bacterial infection is nosocomial in origin. DNA finger printing method can be useful with this aim in view.

CASE REPORTS

A 11 month-old girl suffered from a febrile pneumonia. She developed acute meningitis 15 days later; culture of CSF grew Streptococcus pneumoniae, serotype 23 F, resistant to beta-lactamines, erythromycin and cotrimoxazole. She died 24 hours later. Five days after this death, a 5 month-old infant hospitalized in the next bed developed an acute pulmonary infection due to the same strain with the same bacterial characteristics; this patient was cured with cefotaxime plus vancomycin and gentamicin. Randomly amplified polymorphic DNA analysis showed an identical profile of both strains.

CONCLUSION

This is the first case of meningitis due to penicillin-resistant Streptococcus pneumoniae (PRSP) associated with nosocomial spread between two children in adjacent beds. This case suggests that it is necessary to isolate patients with PRSP infection during hospitalization.

Complement component deficiencies and infection: C5, C8 and C3 deficiencies in three families

Three families are described with complement component deficiencies. In one family, five children had C5 deficiency; in a second family, two children had C8 deficiency and one child in a third family had C3 deficiency. The index cases were identified during screening of patients with recurrent pyogenic infections, recurrent meningitis and meningococcaemia. Two of the five C5 deficient patients had recurrent meningitis and meningococcaemia, two had recurrent respiratory tract infections and otitis and one was healthy. One of the C8 deficient patients had meningitis, meningococcaemia and pneumonia, whereas his sibling with the same deficiency was healthy. The patient with C3 deficiency had four episodes of meningitis and recurrent otitis.

A family with partial and total deficiency of complement C3

A young White girl was found to have no detectable complement C3 or C1q. She suffered repeated attacks of pneumococcal meningitis and pneumococcal pneumonia. Her parents, and some of her siblings, had half the normal level of C3; other siblings were normal. She also had decreased IgG levels and increased IgM concentrations. These findings are correlated with a dysmorphic state of the germinal centres of the peripheral lymphoid tissues, seen after death.