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Ultrastructural localization of albumin transport across the cerebral microvasculature during experimental meningitis in the rat.

Injury to the blood brain barrier (BBB) is a fundamental sequela of bacterial meningitis, yet the precise mechanism facilitating exudation of albumin across the endothelium of the cerebral microvasculature remains conjectural. After intracisternal inoculation of Escherichia coli (0111:B4) lipopolysaccharide in rats to elicit a reversible meningitis and BBB injury, we utilized in situ tracer perfusion and immunolabeling procedures to identify by transmission electron microscopy the precise topography and microvascular exit pathway(s) of bovine serum albumin (BSA). Results revealed that during meningitis there was: (a) an inducible increase in immunodetectable monomeric BSA binding to the luminal membrane of all microvascular segments in the pia-arachnoid and superficial brain cortex; (b) similar uptake of both colloidal Au-BSA (as well as monomeric BSA) by plasmalemmal vesicles but no detectable transcytosis to the abluminal side; and (c) predominant exit of both perfused Au-BSA and immunodetectable monomeric BSA through open intercellular junctions of venules in the pia-arachnoid. This was corroborated in separate experiments documenting focal pial venular leaks of in situ perfused 0.01% colloidal carbon black during experimental meningitis. These results provide precise localization of BBB injury in meningitis to meningeal venules, confirm a paracellular exit pathway of albumin via open intercellular junctions, and suggest an injury mechanism amenable to specific therapeutic intervention.

Animals↗

Adults with meningitis caused by oxacillin-resistant Staphylococcus aureus.

Since 1995, 11 adult patients with oxacillin-resistant Staphylococcus aureus (ORSA) meningitis have been identified at Chang Gung Memorial Hospital-Kaohsiung, in Kaohsiung, Taiwan. The 11 patients were 8 men and 3 women, aged 17-78 years. A postneurosurgical state was an underlying condition for all, and fever and disturbances in consciousness were the most common clinical manifestations. Infection with S. aureus only was found in 8 patients, and mixed infection was found in the other 3. The 8 patients with meningitis caused by S. aureus only were mainly treated with intravenous vancomycin, 2-4 g/day; 4 of these patients died. Although ORSA meningitis is uncommon among adults with culture-proven bacterial meningitis, its incidence has been increasing in recent years. The diagnosis of adult ORSA meningitis can be confirmed only with a positive culture of cerebrospinal fluid, and the choice of initial empirical antibiotics must be guided by the accumulated data concerning the relative frequency of the implicated pathogens found at each institution. Despite the high rate of mortality associated with ORSA meningitis, intravenous vancomycin therapy seems to be one of the best choices for management of this condition in adults.

Adolescent↗

Cognitive impairment in adults with good recovery after bacterial meningitis.

Adults without neurologic sequelae after bacterial meningitis are supposed to live without restrictions. Neuropsychological outcome was assessed in 51 adults from a prospective cohort with good recovery, defined as Glasgow Outcome Scale score 5, after pneumococcal or meningococcal meningitis. Patients who recovered well after pneumococcal meningitis showed cognitive slowness (P=.001). A cognitive disorder was found in 27% of these patients. Patients who previously had meningococcal meningitis were not significantly different from control subjects. Scores on general health and quality of life questionnaires revealed lower scores for patients with meningitis, which were related to cognitive slowing (R, -0.46 to -0.38). In conclusion, adults surviving pneumococcal meningitis were at significant risk of neuropsychological abnormalities, even if they were clinically well recovered.

Adolescent↗

Identification and characterization of Escherichia coli RS218-derived islands in the pathogenesis of E. coli meningitis.

BACKGROUND: Escherichia coli K1 is the most common gram-negative bacterium causing neonatal meningitis, but the mechanisms by which E. coli K1 causes meningitis are not clear. METHODS: We identified 22 E. coli RS218-derived genomic islands (RDIs), using a comparative genome analysis of meningitis-causing E. coli K1 strain RS218 (O18:K1:H7) and laboratory K-12 strain MG1655. Series of RDI deletion mutants were constructed and examined for phenotypes relevant to E. coli K1 meningitis. RESULTS: We identified 9 RDI deletion mutants (RDI 1, 4, 7, 12, 13, 16, 20, 21, and 22) that exhibited defects in meningitis development. RDI 16 and 21 mutants had profound defects in the induction of a high level of bacteremia in neonatal rats, and RDI 4 mutants exhibited a moderate defect in the induction of bacteremia. RDI 1 and 22 mutants showed defects in the ability to invade human brain microvascular endothelial cells (HBMECs), and RDI 12 mutants were defective in the ability to bind to HBMECs. RDI 13 and 20 mutants were defective in the ability to both bind to and invade HBMECs. RDI 7 mutants were defective in the induction of bacteremia and in the ability to both bind to and invade HBMECs. CONCLUSIONS: These results provide a framework for the future discovery and analysis of bacteremia and meningitis caused by E. coli K1 strain RS218.

Animals↗

Epidemiological and molecular characteristics of a highly lethal pneumococcal meningitis epidemic in Burkina Faso.

BACKGROUND: Public health and clinical strategies for meningitis epidemics in sub-Saharan Africa usually assume that Neisseria meningitidis infection causes most disease. METHODS: During 24 months from 2002 to 2005, we collected clinical and laboratory information for suspected acute bacterial meningitis cases from 3 districts in Burkina Faso. Streptococcus pneumoniae was identified by culture, polymerase chain reaction, or antigen detection in cerebrospinal fluid. Pneumococcal genotyping was performed on strains using multilocus variable-number tandem repeat typing and multilocus sequence typing. RESULTS: Samples of cerebrospinal fluid were collected from 1686 persons; 249 (15%) had S. pneumoniae identified (annual incidence, 14 cases per 100,000 persons). Of these patients, 115 (46%) died, making S. pneumoniae the most commonly identified organism and responsible for two-thirds of deaths due to bacterial meningitis. During the meningitis epidemic season, an average of 38 cases of S. pneumoniae infection were identified each month, compared with an average of 8.7 cases during other months. Of 48 pneumococci that were tested, 21 (44%) were identified as serotype 1, and the remaining 27 (56%) were identified as 15 different serogroups and/or serotypes. Both serotype 1 and other serogroups and/or serotypes were seasonal. The genotypes of serotype 1 isolates were closely related but diversified over the study period and were similar to, but not identical to, the predominant genotypes found previously in Ghana. CONCLUSIONS: Intervention strategies during the epidemic season in Burkina Faso (and perhaps elsewhere) must now account for pneumococcal meningitis occurring in an epidemic pattern similar to meningococcal meningitis. Although a serotype 1 clone was commonly isolated, over half of the cases were caused by other serogroups and/or serotypes, and genetic diversification increased over a relatively short period.

Adolescent↗

Cryptococcal meningitis in human immunodeficiency virus-infected patients in Harare, Zimbabwe.

A prospective observational study was conducted over a 10-month period to determine the clinical and laboratory manifestations of cryptococcal meningitis in Zimbabwe, a country where antifungal agents are not widely available. Eighty-nine patients with cryptococcal meningitis (median age, 34 years; range, 11-63 years; 56 males) were identified from 406 patients for whom a clinical diagnosis of meningitis had been made. All patients tested were positive for antibody to human immunodeficiency virus. Cryptococcal meningitis was the first AIDS-defining illness in 88% of patients. Typical presentations were headache, mental impairment, and meningism (median duration, 14 days; range, 1-180 days). The median CD4+ cell count was 70/microL (range, 0-651/microL). The cumulative median survival from the time of diagnosis was 14 days (range, 0-233 days); 22% of patients survived for >30 days. Independent indicators of a good prognosis were not identified. This study provides a unique basis for the development of novel management strategies for patients with cryptococcal meningitis who reside in resource-poor countries.

AIDS-Related Opportunistic Infections↗

The natural history of coccidioidal meningitis: VA-Armed Forces cooperative studies, 1955-1958.

From records on the clinical course of 699 military and veteran patients who had coccidioidomycosis before the advent of effective antifungal therapy, we identified 25 cases in which the manifestations of meningeal dissemination were described. Of 21 patients who had an identifiable initial infection, 16 developed meningeal symptoms (most frequently headache, vomiting, and nuchal rigidity) within the next 6 months. Associated pulmonary lesions were significantly more frequent in the right than in the left lung, as was also the case among 47 matched control patients who had coccidioidomycosis but not meningitis. Of 17 patients whose meningeal symptoms developed during the period studied, all died within 31 months. However, four of eight patients whose onset of symptoms preceded the study period survived for 55-146 months. Patients whose extrapulmonary dissemination involved only the meninges survived significantly longer than did those with more extensive infections. Even without therapy, the white blood cell count in cerebrospinal fluid markedly decreased during the course of the infection. The quantitative analysis provided herein offers a basis for meaningful comparisons with patients enrolled in current and future trials of therapy for coccidioidal meningitis.

Adolescent↗

Overview: treatment of cryptococcal meningitis.

Infections caused by Cryptococcus neoformans cause significant morbidity and high mortality, particularly among immunocompromised patients. Cryptococcal meningitis is an important cause of central nervous system disease and death in patients with AIDS. Although the introduction of amphotericin B has greatly improved the prognosis of patients with cryptococcal meningitis, 30 years of experience have revealed important clinical limitations, including modest efficacy, nephrotoxicity, other clinically significant toxicities, and the inconvenience of intravenous dosing. The discovery of the additive effects of amphotericin B and flucytosine in cryptococcosis resulted in some improvement in efficacy and reduction in amphotericin B-related toxicity. However, approximately 30% of patients with cryptococcal meningitis still fail to respond to therapy. Ketoconazole has not proved useful in treating cryptococcal meningitis. Accumulating evidence suggests that the antifungal triazoles fluconazole, itraconazole, and SCH 39304 represent an advance in the treatment of cryptococcal meningitis, particularly in AIDS patients. Preliminary clinical trials in patients with and without AIDS have indicated that fluconazole and intraconazole are effective and well tolerated as either initial or maintenance therapy. Two large comparative trials of fluconazole and amphotericin B in patients with cryptococcal meningitis (mostly those with AIDS) are under way.

Acquired Immunodeficiency Syndrome↗

Gram-negative meningitis associated with transsphenoidal surgery: case reports and review.

We present a systematic review of meningitis associated with transsphenoidal surgery. Patients present within the first 4 days after surgery with symptoms of headache, fever, and confusion. Overt cerebrospinal rhinorrhea or nuchal rigidity at the time of presentation is an infrequent finding. Although postoperative aseptic meningitis may be difficult to distinguish from early bacterial meningitis, the findings of hypoglycorrhachia, pleocytosis, and hyperproteinemia in the setting of fever and neurological deficit strongly suggest bacterial infection. The preponderance of cases of gram-negative meningitis observed in this series and in previous reports related to posttraumatic CSF leaks indicates that empirical regimens should include agents suitable for treating infections caused by nosocomial pathogens. In general, patients with uncomplicated meningitis in this setting can be expected to recover and do well. Questions remain as to the role of prophylactic antibiotics in the development of gram-negative meningitis in the setting of transsphenoidal surgery. A multicenter trial might be better able to define this role.

Aged↗

Mechanisms of brain injury in bacterial meningitis: workshop summary.

Morbidity and mortality associated with bacterial meningitis remain high, although antibiotic therapy has improved during recent decades. The major intracranial complications of bacterial meningitis are cerebrovascular arterial and venous involvement, brain edema, and hydrocephalus with a subsequent increase of intracranial pressure. Experiments in animal models and cell culture systems have focused on the pathogenesis and pathophysiology of bacterial meningitis in an attempt to identify the bacterial and/or host factors responsible for brain injury during the course of infection. An international workshop entitled "Bacterial Meningitis: Mechanisms of Brain Injury" was organized by the Department of Neurology at the University of Munich and was held in Eibsee, Germany, in June 1993. This conference provided a forum for the exchange of current information on bacterial meningitis, including data on the clinical spectrum of complications, the associated morphological alterations, the role of soluble inflammatory mediators (in particular cytokines) and of leukocyte-endothelial cell interactions in tissue injury, and the molecular mechanisms of neuronal injury, with potential mediators such as reactive oxygen species, reactive nitrogen species, and excitatory amino acids. It is hoped that a better understanding of the pathophysiological events that take place during bacterial meningitis will lead to the development of new therapeutic regimens.

Animals↗

Herpes simplex virus type 2 meningitis in the absence of genital lesions: improved recognition with use of the polymerase chain reaction.

Herpes simplex virus type 2 (HSV-2) is known to cause aseptic meningitis, which can be recurrent. The diagnosis of HSV-2 infection is suggested when meningitis occurs simultaneously with genital lesions but may be obscure if genital lesions are not present or are not appreciated. Viral culture of the CSF is sometimes positive, but it may also be negative, especially in cases of recurrent disease. We report three cases of HSV meningitis in young women who did not have a history of genital herpetic lesions and for whom genital lesions were not noted on presentation. With use of the polymerase chain reaction (PCR), HSV DNA was detected in CSF from all three patients. The diagnosis of HSV meningitis was further confirmed by a positive culture of CSF in one patient's case and by demonstration of intrathecal synthesis of HSV antibodies in a second patient's case. The use of PCR can improve the recognition of HSV meningitis in adults presenting with aseptic meningitis, even in the absence of herpetic lesions.

Adult↗

Nontuberculous mycobacterial meningitis: report of two cases and review.

Nontuberculous mycobacterial meningitis (NTMM) is still a rare disease despite the increase in the number of cases of disseminated mycobacterial infection related to the AIDS epidemic. Moreover, there are doubts as to the clinical relevance of the isolation of mycobacteria other than Mycobacterium tuberculosis from cerebrospinal fluid. After analyzing the clinical and pathological data, we classified the cases of NTMM into three groups: definitive (28 cases), probable (19), and doubtful (5). We found that Mycobacterium avium is the most commonly isolated species (60% of cases). M. avium meningitis presents as a disseminated disease, is usually related to serious underlying conditions (mainly immunosuppression), and is associated with a death rate that approaches 70%. Mycobacterium fortuitum meningitis is associated with previous neurosurgery or back trauma; the prognosis for this infection is better when the concomitant abscesses are drained. The clinical characteristics of Mycobacterium kansasii meningitis are similar to those of M. tuberculosis meningitis, but the mortality related to M. kansasii meningitis is high despite appropriate antibiotic treatment. Herein, we present two cases of NTMM that occurred at our center, and we review 50 additional cases reported in the English-language literature.

AIDS-Related Opportunistic Infections↗

Treatment of gram-negative bacillary meningitis: role of the new cephalosporin antibiotics.

Results of the treatment of gram-negative bacillary meningitis have been disappointing: mortality is extremely high, and treatment with chloramphenicol has shown a high failure rate. This failure rate for chloramphenicol is consistent with the wide gap between minimal inhibitory concentration and minimal bactericidal concentration of this drug for Escherichia coli, Klebsiella, and other Enterobacteriaceae. Cefotaxime, a new cephalosporin, is cidal for most gram-negative bacteria at concentrations of less than 0.25 microgram/ml. By late 1981, 137 patients with meningitis due to a variety of bacteria had been treated with this agent. Bacteriologic cure rates were 93% for meningitis due to Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae and 88% for meningitis due to gram-negative bacteria (94.4% for meningitis due to E. coli and Klebsiella). This new antibiotic shows considerable promise in the treatment of these forms of meningitis.

Adult↗

Radioimmunoassay for detecting Mycobacterium tuberculosis antigen in cerebrospinal fluids of patients with tuberculous meningitis.

A biotin-avidin radioimmunoassay for detecting Mycobacterium tuberculosis antigen has been developed. The assay involves sandwiching mycobacterial antigens from sonicate preparations and cerebrospinal fluids between two antibodies produced in burros and rabbits. The reaction is amplified by using biotinylated antibody to rabbit IgG and 125I-labeled avidin. The assay has a sensitivity of 20 ng/ml and shows less than 5% cross-reactivity with six other mycobacteria. We studied patients with untreated tuberculous meningitis, patients with treated tuberculous meningitis, patients with nonbacterial meningitis, and patients with bacterial meningitis. Antigen was detectable in two of 56 control samples (40 ng/ml). Hence, samples with greater than or equal to 80 ng of antigen/ml were considered positive. In patients with untreated tuberculous meningitis, antigen levels ranged from 20 to 10,000 ng/ml, and 15 (79%) of 19 samples were positive. In the treated group, only two (10%) of 17 samples were positive. This test promises to be a rapid adjunct in the early diagnosis of tuberculous meningitis.

Antigens, Bacterial↗

Influence of granulocytes on brain edema, intracranial pressure, and cerebrospinal fluid concentrations of lactate and protein in experimental meningitis.

Brain water content (brain edema), intracranial pressure, and cerebrospinal fluid (CSF) concentrations of lactate and protein increased significantly during 24 h of experimental meningitis due to Streptococcus pneumoniae, but changes were similar in normal and neutropenic rabbits. In sterile meningitis induced by N-formyl-methionyl-leucyl-phenyl-alanine (fMLP), low and high doses of fMLP were equally effective in inducing CSF pleocytosis, whereas only high doses of fMLP caused brain edema. High doses of fMLP injected intracisternally during pneumococcal meningitis also increased brain water content. The fMLP did not significantly increase intracranial pressure or CSF concentrations of lactate or protein in sterile or pneumococcal meningitis, nor did it cause brain edema in neutropenic animals. Thus, granulocytes may contribute to brain edema during meningitis if adequately stimulated, but intracranial pressure and CSF protein and lactate concentrations appear independent of granulocytes. Stimulation does not appear to occur early in meningitis, when granulocytes were without effect on brain edema.

Animals↗

Primary and recurrent herpes simplex virus type 2-induced meningitis.

In 27 patients with a first episode of herpes simplex virus type 2 (HSV-2)-induced meningitis, confirmed by virus isolation from the cerebrospinal fluid (CSF) or seroconversion to HSV-2, initial neurologic complications were found in 10 (37%) but subsided before 6 months in all patients. Long-term complications were recurrent meningitis in 5 (19%) and periodic headache related to genital HSV recrudescences in 4 (15%). Seven additional patients had possible HSV-2-induced recurrent meningitis. In contrast to the first episode of meningitis, virus isolation, HSV antigen detection, and IgG analyses in consecutive serum samples were of no diagnostic value in episodes of HSV-2-induced recurrent meningitis. Instead, immunoblotting was used to assay intrathecally produced IgG antibodies to the HSV-2 type-specific protein gG-2 in recurrent meningitis, when CSF was collected at a minimum of 3 days after onset.

Antibodies, Viral↗

Factors influencing the anti-inflammatory effect of dexamethasone therapy in experimental pneumococcal meningitis.

Dexamethasone (DXM) interferes with the production of tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1) and can thereby diminish the secondary inflammatory response that follows initiation of antibacterial therapy. A beneficial effect on the outcome of Haemophilus meningitis in children has been proven, but until recently the effect of DXM therapy in pneumococcal meningitis was uncertain. The aim of the present study was to evaluate factors that might influence the modulatory effect of DXM on the antibiotic-induced inflammatory response in a rabbit model of pneumococcal meningitis. DXM (1 mg/kg) was given intravenously 30 min before or 1 h after administration of a pneumococcal cell wall extract, or the first dose of ampicillin. In meningitis induced by cell wall extract, DXM therapy prevented the increase in cerebrospinal fluid (CSF) leucocyte and lactate concentrations, but only if given 30 min before the cell wall extract. In meningitis caused by live organisms, initiation of ampicillin therapy resulted in an increase in CSF TNF-alpha and lactate concentrations only in animals with initial CSF bacterial concentrations > or =5.6 log10 cfu/mL. In those animals, DXM therapy prevented significant elevations in CSF TNF-alpha [median change -184 pg/mL, -114 pg/mL versus +683 pg/mL with DXM (30 min before or 1 h after ampicillin) versus controls (no DXM), respectively, P=0.02] and lactate concentrations [median change -10.6 mmol/L, -1.5 mmol/L versus +14.3 mmol/L with DXM (30 min before or 1 h after ampicillin) versus controls (no DXM), respectively, P=0.01]. These effects were independent of the timing of DXM administration. In this model of experimental pneumococcal meningitis, an antibiotic-induced secondary inflammatory response in the CSF was demonstrated only in animals with high initial CSF bacterial concentrations (> or =5.6 log10 cfu/mL). These effects were modulated by DXM therapy whether it was given 30 min before or 1 h after the first dose of ampicillin.

Animals↗

Lack of endothelial nitric oxide synthase aggravates murine pneumococcal meningitis.

Nitric oxide (NO) plays a central role in the pathogenesis of bacterial meningitis. However, the role of NO produced by endothelial NO synthase (eNOS) in meningitis is still unclear. We investigated the influence of eNOS depletion on the inflammatory host response, intracranial complications, and outcome in experimental pneumococcal meningitis. Leukocyte accumulation in the cerebrospinal fluid was more pronounced in infected eNOS-deficient mice than in infected wild type mice. This effect could be attributed to an increased expression of P-selectin, macrophage inflammatory protein-2, keratinocyte-derived cytokine, and interleukin (IL)-1beta in the brain of infected eNOS-deficient mice. However, no differences in the cerebral expression of intercellular adhesion molecule-1, tumor necrosis factor-alpha, and IL-6 as well as of neuronal NOS and inducible NOS could be detected between infected wild type and mutant mice. In addition to enhanced leukocyte infiltration into the CSF, meningitis-associated intracranial complications including blood-brain barrier disruption and the rise in intracranial pressure were significantly augmented in infected eNOS-deficient mice. The aggravation of intracranial complications was paralleled by a worsening of the disease, as evidenced by a more pronounced hypothermia, an enhanced weight reduction, and an increased death rate. The current data indicate that eNOS deficiency is detrimental in bacterial meningitis. This effect seems to be related to an increased expression of (certain) cytokines/chemokines and adhesion molecules; thus leading to increased meningeal inflammation and, subsequently, to aggravated intracranial complications.

Animals↗