Bacterial meningitis: current therapy and possible future treatment options

Despite targeted therapy, case-fatality rates and neurologic sequelae of bacterial meningitis remain unacceptably high. The poor outcome is mainly due to secondary systemic and intracranial complications. These complications seem to be both a consequence of the inflammatory response to the invading pathogen and release of bacterial components by the pathogen itself. Therefore, within the last decades, research has focused on the mechanism underlying immune regulation and the inhibition of bacterial lysis in order to identify new targets for adjuvant therapy. The scope of this article is to give an overview on current treatment strategies of bacterial meningitis, to summarize new insights on the pathophysiology of bacterial meningitis, and to give an outlook on new treatment strategies derived from experimental models.

Bacterial meningitis impairs hippocampal neurogenesis

Bacterial meningitis causes persisting neurofunctional sequelae. Theoccurrence of apoptotic cell death in the hippocampal subgranular zone of the dentate gyrus characterizes the disease in patients and relates to deficits in learning and memory in corresponding experimental models. Here, we investigated why neurogenesis fails to regenerate the damage in the hippocampus associated with the persistence of neurofunctional deficits. In an infant rat model of bacterial meningitis, the capacity of hippocampal-derived cells to multiply and form neurospheres was significantly impaired comparedto that in uninfected littermates. In an in vitro model of differentiating hippocampal cells, challenges characteristic of bacterial meningitis (i.e. bacterial components, tumor necrosis factor [20 ng/mL], or growth factor deprivation) caused significantly more apoptosis in stem/progenitor cells and immature neurons than in mature neurons. These results demonstrate that bacterial meningitis injures hippocampal stem and progenitor cells, a finding that may explain the persistence of neurofunctional deficits after bacterial meningitis.

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.

Intussusceptive angiogenesis: a biologically relevant form of angiogenesis

Angiogenesis, i.e. the development and growth of blood vessels, is a major topic of research as it plays an important role in normal development and in various pathologies. Recent evidence revealed the existence of different mechanisms of blood vessel growth, including sprouting and intussusceptive angiogenesis, vascular mimicry, and blood vessel cooption. The latter two have only been observed in tumor growth, but sprouting and intussusceptive angiogenesis also occur in healthy, physiologically growing tissues. Despite this variety of angiogenic mechanisms, most of the current research is focused on the mechanism of sprouting angiogenesis because this mechanism was first described and because most existing experimental models are related to sprouting angiogenesis. Consequently, the mechanism of intussusceptive angiogenesis is often overlooked in angiogenesis research. Here, the mechanism of intussusceptive angiogenesis is reviewed and the current techniques and models for investigating intussusceptive angiogenesis are summarized. In addition, other mechanisms of vascular growth are briefly reviewed.

Sodium nitroprusside induces cell death and cytoskeleton degradation in adult rat cardiomyocytes in vitro: implications for anthracycline-induced cardiotoxicity

Sodium nitroprusside (SNP) is used clinically as a rapid-acting vasodilator and in experimental models as donor of nitric oxide (NO). High concentrations of NO have been reported to induce cardiotoxic effects including apoptosis by the formation of reactive oxygen species. We have therefore investigated effects of SNP on the myofibrillar cytoskeleton, contractility and cell death in long-term cultured adult rat cardiomyocytes at different time points after treatment. Our results show, that SNP treatment at first results in a gradual increase of cytoskeleton degradation marked by the loss of actin labeling and fragmentation of sarcomeric structure, followed by the appearance of TUNEL-positive nuclei. Already lower doses of SNP decreased contractility of cardiomyocytes paced at 2 Hz without changes of intracellular calcium concentration. Ultrastructural analysis of the cultured cells demonstrated mitochondrial changes and disintegration of sarcomeric alignment. These adverse effects of SNP in cardiomyocytes were reminiscent of anthracycline-induced cardiotoxicity, which also involves a dysregulation of NO with the consequence of myofibrillar degradation and ultimately cell death. An inhibition of the pathways leading to the generation of reactive NO products, or their neutralization, may be of significant therapeutic benefit for both SNP and anthracycline-induced cardiotoxicity.

[Kidney and smoking: literature review and focus]

Smoking remains a major public health problem. It is associated with a considerable number of deaths in the world's population. Smoking is just like high blood pressure, an independent predictor of progression to any primary renal disease and renal transplant patients. It seems that smoking cessation slows the progression of kidney disease in smokers. The literature data are sometimes contradictory about it because of some methodological weaknesses. However, experimental models highlight the harmful effects of tobacco by hemodynamic and non-hemodynamic factors. The conclusion is that a major effort should be further produced by the nephrology community to motivate our patients to stop smoking.

Strategies to prevent neuronal damage in paediatric bacterial meningitis

PURPOSE OF REVIEW: The mortality of bacterial meningitis can reach 30%, and up to 50% of survivors suffer from persisting neurological deficits as a consequence of the disease. The incidence of neurological sequelae of bacterial meningitis has not improved over the last decade. Adjunctive therapeutic options are limited, and ongoing research into the pathophysiology of brain damage in bacterial meningitis aims at providing the scientific basis for future development of more efficient adjunctive options. RECENT FINDINGS: In a population with good access to health care, dexamethasone given before or at the time of initiation of antibiotic therapy acts beneficially in paediatric pneumococcal meningitis, but not in meningococcal meningitis. In experimental animal models, brain-derived neurotrophic factor protected against brain injury and improved hearing while melatonin, which has antioxidant properties among other effects, reduced neuronal death. Transgene technology can be used to provide new insights into the pathophysiology of the disease and to identify potential therapeutic targets. SUMMARY: Although dexamethasone improves outcome of bacterial meningitis under defined circumstances, the morbidity of bacterial meningitis still remains unacceptably high. Experimental models may help to identify new therapeutic strategies to further improve the neurological outcome in young children suffering from bacterial meningitis.

The in vitro evidence for an effect of high homeopathic potencies--a systematic review of the literature

OBJECTIVE: Systematic assessment of the in vitro research on high potency effects. METHOD: Publications of experiments were collected through databases, experts, previous reviews, citation tracking. Inclusion criteria: stepwise agitated dilutions <10(-23); cells or molecules from human or animal. Experiments were assessed with the modified SAPEH score. RESULTS: From 75 publications, 67 experiments (1/3 of them replications) were evaluated. Nearly 3/4 of them found a high potency effect, and 2/3 of those 18 that scored 6 points or more and controlled contamination. Nearly 3/4 of all replications were positive. Design and experimental models of the reviewed experiments were inhomogenous, most were performed on basophiles. CONCLUSIONS: Even experiments with a high methodological standard could demonstrate an effect of high potencies. No positive result was stable enough to be reproduced by all investigators. A general adoption of succussed controls, randomization and blinding would strengthen the evidence of future experiments.

Percutaneous technique for creation of tricuspid regurgitation in an ovine model

Experimental models of tricuspid regurgitation (TR) are needed to study the percutaneous placement of prosthetic atrioventricular valves. The purpose of this study was to develop an appropriate simple and reproducible percutaneous experimental model for creation of tricuspid regurgitation. Tricuspid regurgitation was successfully created through papillary muscle avulsion using a guide-wire loop in seven sheep with regurgitation documented on right ventricular angiograms and a significant increase in heart rate and right atrial pressures. Acute onset of tricuspid regurgitation was poorly tolerated in one animal that died. Autopsy examinations showed avulsion of one papillary muscle in four animals and two papillary muscles in three animals.

Double-lung transplantation in the rat: an acute, syngeneic in situ model

BACKGROUND. The high rate of reperfusion injury in clinical lung transplantation mandates significant improvements in lung preservation. Innovations should be validated using standardized and low-cost experimental models. METHODS. The model introduced here is analyzed by comparing global lung function after varying ischemic times (2, 4, 8, 16, and 24 hours). A rat double-lung block is flush-perfused, and the main pulmonary artery and left atrium are connected to the left pulmonary artery and vein of a syngeneic recipient using a T-shaped stent. With pressure side ports and incorporated flow crystals, measurement of vascular resistance and graft oxygenation can be performed. The transplant is ventilated separately, and compliance and resistance are determined. RESULTS. The increase in the ischemic interval from 2 to 24 hours caused an increase in the alveolar arterial oxygen difference from 220 +/- 20 to 600 +/- 34 mm Hg, pulmonary vascular resistance from 198 +/- 76 to 638 +/- 212 mm Hg.mL-1.min-1, and resistance to airflow from 274 +/- 50 to 712 +/- 30 cm H2O/L H2O, and a decrease in pulmonary compliance from 0.4 +/- 0.05 to 0.12 +/- 0.06 mL/cm H2O. CONCLUSIONS. This in situ, syngeneic rat lung transplantation model offers an alternative to large animal models for verification of lung preservation solutions and for modification of donor or recipient treatment regimens.

The antioxidant glutathione in the fish cell lines EPC and BCF-2: response to model pro-oxidants as measured by three different fluorescent dyes

Reduced glutathione (GSH) protects cells against injury by oxidative stress and maintains a range of vital functions. In vitro cell cultures have been used as experimental models to study the role of GSH in chemical toxicity in mammals; however, this approach has been rarely used with fish cells to date. The present study aimed to evaluate sensitivity and specificity of three fluorescent dyes for measuring pro-oxidant-induced changes of GSH contents in fish cell lines: monochlorobimane (mBCl), 5-chloromethylfluorescein diacetate (CMFDA) and 7-amino-4-chloromethylcoumarin (CMAC-blue). Two cell lines were studied, the EPC line established from a skin tumour of carp Cyprinus carpio, and BF-2 cells established from fins of bluegill sunfish Lepomis macrochirus. The cells were exposed for 6 and 24 h to low cytotoxic concentrations of pro-oxidants including hydrogen peroxide, paraquat (PQ), copper and the GSH synthesis inhibitor, L-buthionine-SR-sulfoximine (BSO). The results indicate moderate differences in the GSH response between EPC and BF-2 cells, but distinct differences in the magnitude of the GSH response for the four pro-oxidants. Further, the choice of GSH dye can critically affect the results, with CMFDA appearing to be less specific for GSH than mBCl and CMAC-blue.

NaV1.5 and interacting proteins in human arrhythmogenic cardiomyopathy

Evaluation of: Noorman M, Hakim S, Kessler E et al. Remodeling of the cardiac sodium channel, connexin43, and plakoglobin at the intercalated disk in patients with arrhythmogenic cardiomyopathy. Heart Rhythm 10(3), 412-419 (2013). Arrhythmogenic cardiomyopathy (AC) is a heart muscle disease characterized by a progressive replacement of the ventricular myocardium with adipose and fibrous tissue. This disease is often associated with mutations in genes encoding desmosomal proteins in the majority of patients. Based on results obtained from recent experimental models, a disturbed distribution of gap junction proteins and cardiac sodium channels may also be observed in AC phenotypes, secondary to desmosomal dysfunction. The study from Noorman et al. examined heart sections from patients diagnosed with AC and performed immunohistochemical analyses of N-cadherin, PKP2, PKG, Cx43 and the cardiac sodium channel NaV1.5. Altered expression/distribution of Cx43, PKG and NaV1.5 was found in most cases of patients with AC. The altered expression and/or distribution of NaV1.5 channels in AC hearts may play a mechanistic role in the arrhythmias leading to sudden cardiac death in AC patients. Thus, NaV1.5 should be considered as a supplemental element in the evaluation of risk stratification and management strategies. However, additional experiments are required to clearly understand the mechanisms leading to AC phenotypes.

Modern charge density studies: the entanglement of experiment and theory

This tutorial review article is intended to provide a general guidance to a reader interested to learn about the methodologies to obtain accurate electron density mapping in molecules and crystalline solids, from theory or from experiment, and to carry out a sensible interpretation of the results, for chemical, biochemical or materials science applications. The review mainly focuses on X-ray diffraction techniques and refinement of experimental models, in particular multipolar models. Neutron diffraction, which was widely used in the past to fix accurate positions of atoms, is now used for more specific purposes. The review illustrates three principal analyses of the experimental or theoretical electron density, based on quantum chemical, semi-empirical or empirical interpretation schemes, such as the quantum theory of atoms in molecules, the semi-classical evaluation of interaction energies and the Hirshfeld analysis. In particular, it is shown that a simple topological analysis based on a partition of the electron density cannot alone reveal the whole nature of chemical bonding. More information based on the pair density is necessary. A connection between quantum mechanics and observable quantities is given in order to provide the physical grounds to explain the observations and to justify the interpretations.

Small ruminant lentivirus genotype B and E interaction: evidences on the role of Roccaverano strain on reducing proviral load of the challenging CAEV strain

Live attenuated vaccines provide the most consistent protective immunity in experimental models of lentivirus infections. In this study we tested the hypothesis that animals infected with a naturally attenuated small ruminant lentivirus field strain of genotype E may control a challenge infection with a virulent strain of the caprine arthritis encephalitis virus (CAEV-CO). Within genotype E, Roccaverano strain has been described as attenuated since decreased arthritic pathological indexes were recorded in Roccaverano-infected animals compared to animals of the same breed infected with genotype B strains. Moreover, under natural conditions, animals double-infected with genotypes B and E appear less prone to develop SRLV-related disease, leading to a putative protective role of Roccaverano strain. Here we present evidence that goats experimentally infected with the avirulent genotype E SRLV-Roccaverano strain control the proviral load of a pathogenic challenge virus (CAEV-CO strain) more efficiently than naïve animals and appear to limit the spread of histological lesions to the contralateral joints.

Large scale variation in Enterococcus faecalis illustrated by the genome analysis of strain OG1RF.

BACKGROUND: Enterococcus faecalis has emerged as a major hospital pathogen. To explore its diversity, we sequenced E. faecalis strain OG1RF, which is commonly used for molecular manipulation and virulence studies. RESULTS: The 2,739,625 base pair chromosome of OG1RF was found to contain approximately 232 kilobases unique to this strain compared to V583, the only publicly available sequenced strain. Almost no mobile genetic elements were found in OG1RF. The 64 areas of divergence were classified into three categories. First, OG1RF carries 39 unique regions, including 2 CRISPR loci and a new WxL locus. Second, we found nine replacements where a sequence specific to V583 was substituted by a sequence specific to OG1RF. For example, the iol operon of OG1RF replaces a possible prophage and the vanB transposon in V583. Finally, we found 16 regions that were present in V583 but missing from OG1RF, including the proposed pathogenicity island, several probable prophages, and the cpsCDEFGHIJK capsular polysaccharide operon. OG1RF was more rapidly but less frequently lethal than V583 in the mouse peritonitis model and considerably outcompeted V583 in a murine model of urinary tract infections. CONCLUSION: E. faecalis OG1RF carries a number of unique loci compared to V583, but the almost complete lack of mobile genetic elements demonstrates that this is not a defining feature of the species. Additionally, OG1RF's effects in experimental models suggest that mediators of virulence may be diverse between different E. faecalis strains and that virulence is not dependent on the presence of mobile genetic elements.