Pathogenesis of cutaneous lesions in acute meningococcemia in humans: light, immunofluorescent, and electron microscopic studies of skin biopsy specimens

Parainfectious cerebral vasculopathy complicating bacterial meningitis: Acute-short lived vasospasm followed by delayed-long lasting vasculitis

Bacterial meningitis is a serious, life-threatening infection of the meninges. Several radiological studies highlight prominent structural alterations occurring in the cerebral vasculature, leading to significant cerebrovascular consequences during bacterial meningitis. Beginning with reflexive arterial vasospasm , cerebrovascular disease during bacterial meningitis proceeds through a orderly sequence of arterial vasculitis with inflammatory cell infiltration, medial smooth muscle migration and proliferation, medial necrosis, adventitial fibrosis and eventual intimal stenosis. As such, this review focuses on changes occurring within cerebral arteries during disease progression, highlighting the various structural modifications occurring in the arterial vessels that contribute to disturbances in cerebral hemodynamics and, ultimately, cerebrovascular consequences during bacterial meningitis.

The Host-Pathogen Interactions and Epicellular Lifestyle of Neisseria meningitidis

Neisseria meningitidis is a gram-negative diplococcus and a transient commensal of the human nasopharynx. It shares and competes for this niche with a number of other Neisseria species including N. lactamica, N. cinerea and N. mucosa. Unlike these other members of the genus, N. meningitidis may become invasive, crossing the epithelium of the nasopharynx and entering the bloodstream, where it rapidly proliferates causing a syndrome known as Invasive Meningococcal Disease (IMD). IMD progresses rapidly to cause septic shock and meningitis and is often fatal despite aggressive antibiotic therapy. While many of the ways in which meningococci survive in the host environment have been well studied, recent insights into the interactions between N. meningitidis and the epithelial, serum, and endothelial environments have expanded our understanding of how IMD develops. This review seeks to incorporate recent work into the established model of pathogenesis. In particular, we focus on the competition that N. meningitidis faces in the nasopharynx from other Neisseria species, and how the genetic diversity of the meningococcus contributes to the wide range of inflammatory and pathogenic potentials observed among different lineages.

Colonization of dermal arterioles by Neisseria meningitidis provides a safe haven from neutrophils

The human pathogen Neisseria meningitidis can cause meningitis and fatal systemic disease. The bacteria colonize blood vessels and rapidly cause vascular damage, despite a neutrophil-rich inflammatory infiltrate. Here, we use a humanized mouse model to show that vascular colonization leads to the recruitment of neutrophils, which partially reduce bacterial burden and vascular damage. This partial effect is due to the ability of bacteria to colonize capillaries, venules and arterioles, as observed in human samples. In venules, potent neutrophil recruitment allows efficient bacterial phagocytosis. In contrast, in infected capillaries and arterioles, adhesion molecules such as E-Selectin are not expressed on the endothelium, and intravascular neutrophil recruitment is minimal. Our results indicate that the colonization of capillaries and arterioles by N. meningitidis creates an intravascular niche that precludes the action of neutrophils, resulting in immune escape and progression of the infection.

Type IV pilus retraction enables sustained bacteremia and plays a key role in the outcome of meningococcal sepsis in a humanized mouse model

Neisseria meningitidis (the meningococcus) remains a major cause of bacterial meningitis and fatal sepsis. This commensal bacterium of the human nasopharynx can cause invasive diseases when it leaves its niche and reaches the bloodstream. Blood-borne meningococci have the ability to adhere to human endothelial cells and rapidly colonize microvessels. This crucial step enables dissemination into tissues and promotes deregulated inflammation and coagulation, leading to extensive necrotic purpura in the most severe cases. Adhesion to blood vessels relies on type IV pili (TFP). These long filamentous structures are highly dynamic as they can rapidly elongate and retract by the antagonistic action of two ATPases, PilF and PilT. However, the consequences of TFP dynamics on the pathophysiology and the outcome of meningococcal sepsis in vivo have been poorly studied. Here, we show that human graft microvessels are replicative niches for meningococci, that seed the bloodstream and promote sustained bacteremia and lethality in a humanized mouse model. Intriguingly, although pilus-retraction deficient N. meningitidis strain (ΔpilT) efficiently colonizes human graft tissue, this mutant did not promote sustained bacteremia nor induce mouse lethality. This effect was not due to a decreased inflammatory response, nor defects in bacterial clearance by the innate immune system. Rather, TFP-retraction was necessary to promote the release of TFP-dependent contacts between bacteria and, in turn, the detachment from colonized microvessels. The resulting sustained bacteremia was directly correlated with lethality. Altogether, these results demonstrate that pilus retraction plays a key role in the occurrence and outcome of meningococcal sepsis by supporting sustained bacteremia. These findings open new perspectives on the role of circulating bacteria in the pathological alterations leading to lethal sepsis.

An ADAM-10 dependent EPCR shedding links meningococcal interaction with endothelial cells to purpura fulminans

Purpura fulminans is a deadly complication of Neisseria meningitidis infections due to extensive thrombosis of microvessels. Although a Disseminated Intra-vascular Coagulation syndrome (DIC) is frequently observed during Gram negative sepsis, it is rarely associated with extensive thrombosis like those observed during meningococcemia, suggesting that the meningococcus induces a specific dysregulation of coagulation. Another specific feature of N. meningitidis pathogenesis is its ability to colonize microvessels endothelial cells via type IV pili. Importantly, endothelial cells are key in controlling the coagulation cascade through the activation of the potent anticoagulant Protein C (PC) thanks to two endothelial cell receptors among which the Endothelial Protein C Receptor (EPCR). Considering that congenital or acquired deficiencies of PC are associated with purpura fulminans, we hypothesized that a defect in the activation of PC following meningococcal adhesion to microvessels is responsible for the thrombotic events observed during meningococcemia. Here we showed that the adhesion of N. meningitidis on endothelial cells results in a rapid and intense decrease of EPCR expression by inducing its cleavage in a process know as shedding. Using siRNA experiments and CRISPR/Cas9 genome edition we identified ADAM10 (A Disintegrin And Metalloproteinase-10) as the protease responsible for this shedding. Surprisingly, ADAM17, the only EPCR sheddase described so far, was not involved in this process. Finally, we showed that this ADAM10-mediated shedding of EPCR induced by the meningococcal interaction with endothelial cells was responsible for an impaired activation of Protein C. This work unveils for the first time a direct link between meningococcal adhesion to endothelial cells and a severe dysregulation of coagulation, and potentially identifies new therapeutic targets for meningococcal purpura fulminans.

Neisseria meningitidis (meningococcus) is responsible for a severe syndrome called purpura fulminans in which the coagulation system is totally dysregulated, leading to an extensive occlusion of blood microvessels. The pathogenesis of this syndrome is still not understood. Here we show that the meningococcus, when adhering on the apical surface of endothelial cells, induces the activation of membranous protease named ADAM-10, which in turn hydrolyses a cellular receptor called EPCR. The latter is key for the activation of a circulating potent anticoagulant, the Protein C (PC). PC activation is then impaired following meningococcal adhesion on endothelial cells. This work unveils for the first time a specific dysregulation of coagulation induced by the meningococcus and potentially identifies new therapeutic targets for meningococcal purpura fulminans.

Structure of the Neisseria meningitidis Type IV pilus

Neisseria meningitidis use Type IV pili (T4P) to adhere to endothelial cells and breach the blood brain barrier, causing cause fatal meningitis. T4P are multifunctional polymers of the major pilin protein, which share a conserved hydrophobic N terminus that is a curved extended α-helix, α1, in X-ray crystal structures. Here we report a 1.44 Å crystal structure of the N. meningitidis major pilin PilE and a ∼6 Å cryo-electron microscopy reconstruction of the intact pilus, from which we built an atomic model for the filament. This structure reveals the molecular arrangement of the N-terminal α-helices in the filament core, including a melted central portion of α1 and a bridge of electron density consistent with a predicted salt bridge necessary for pilus assembly. This structure has important implications for understanding pilus biology.

Type IV pili are present on a wide range of bacterial pathogens and mediate diverse functions. Here the authors report a high resolution crystal structure of the pilin subunit PilE, and a cryoEM reconstruction of the Type IV pilus filament from N. meningitidis that offer insight into pilus assembly and functions.

Adhesion of Neisseria meningitidis to dermal vessels leads to local vascular damage and purpura in a humanized mouse model

Septic shock caused by Neisseria meningitidis is typically rapidly evolving and often fatal despite antibiotic therapy. Further understanding of the mechanisms underlying the disease is necessary to reduce fatality rates. Postmortem samples from the characteristic purpuric rashes of the infection show bacterial aggregates in close association with microvessel endothelium but the species specificity of N. meningitidis has previously hindered the development of an in vivo model to study the role of adhesion on disease progression. Here we introduced human dermal microvessels into SCID/Beige mice by xenografting human skin. Bacteria injected intravenously exclusively associated with the human vessel endothelium in the skin graft. Infection was accompanied by a potent inflammatory response with the secretion of human inflammatory cytokines and recruitment of inflammatory cells. Importantly, infection also led to local vascular damage with hemostasis, thrombosis, vascular leakage and finally purpura in the grafted skin, replicating the clinical presentation for the first time in an animal model. The adhesive properties of the type IV pili of N. meningitidis were found to be the main mediator of association with the dermal microvessels in vivo. Bacterial mutants with altered type IV pili function also did not trigger inflammation or lead to vascular damage. This work demonstrates that local type IV pili mediated adhesion of N. meningitidis to the vascular wall, as opposed to circulating bacteria, determines vascular dysfunction in meningococcemia.

[Cutaneous vasculitis]

Vasculitis is a term that refers to damage and inflammation of the walls of blood vessels of any size. The classification of types of cutaneous vasculitis continues to be a challenge, probably because of our lack of understanding of the etiology and pathogenesis of this condition. Changes in the vessel wall will be visible on microscopy and will enable the different clinical forms to be distinguished according to the caliber of affected vessels, the type of cell that predominates in the inflammatory infiltrate, or the presence of such key findings as extravascular granulomas. Skin manifestations (macules, papules, nodules, livedo reticularis, etc) correlate with the size of the vessel affected. The prognosis in cases of vasculitis with skin involvement will be determined by the presence or absence of extracutaneous disease. Systemic vasculitis shows a predilection for certain organs, such as the kidney or lung. The introduction of immunosuppressant drug treatments has led to evident improvement in survival rates for patients with vasculitis. This review covers practical aspects of the pathophysiology, histopathology, treatment, and differential diagnosis of the main clinical presentations of vasculitis with cutaneous involvement.

[Septic vasculopathy]

Sepsis is one of the commonest causes of death around the world. The real frequency of cutaneous lesions in the setting of sepsis is unknown, but when they appear, they are usually one of the earliest signs of sepsis, thus allowing a rapid diagnosis of this potentially life-threatening condition. Four are the main physiopathologic mechanisms that can induce cutaneous lesions in sepsis: a) disseminated intravascular coagulation; b) direct vessel wall invasion by the microorganism; c) immune-mediated vasculitis, and d) septic embolism. We know that more than one of these mechanisms can appear in one single patient. In this review, we analyse these four mechanisms, their clinical presentation, and the histological findings that can be found in the cutaneous biopsy.

Severe sepsis and septic shock: the role of gram-negative bacteremia

Abstract Although Gram-negative bacteria have often been implicated in the pathogenesis of severe sepsis and septic shock, how they trigger these often lethal syndromes is uncertain. In particular, the role played by blood-borne bacteria is controversial. This review considers two alternatives. In the first, circulating Gram-negative bacteria induce toxic reactions directly within the vasculature; in the second, the major inflammatory stimulus occurs in local extravascular sites of infection and circulating bacteria contribute little to inducing toxic responses. Evidence for each alternative is found in the literature. Bacteremia and severe sepsis are not so closely linked that the most striking cases can be a model for the rest. Intravascular and extravascular triggers may warrant different approaches to prevention and therapy.

Cutaneous Vasculitis Update: Small Vessel Neutrophilic Vasculitis Syndromes

A broad and diverse spectrum of vasculitic syndromes exists. These syndromes affect the skin with varying levels of associated systemic manifestations, running the gamut from a self-limited, localized, cutaneous phenomenon to rapidly progressive, multiorgan disease. The majority of cases of cutaneous vasculitis will show a neutrophilic small vessel vasculitis that can be either a primary (idiopathic) disorder (eg, cutaneous leukocytoclastic angiitis) or a secondary disorder that is associated with drugs, infection (eg, streptococcal infection, viral hepatitis), or underlying disease (eg, connective tissue disease, malignancy). Biopsy is the gold standard for the diagnosis of cutaneous vasculitis and also necessary for the detection of cutaneous vascular immune complexes by direct immunofluorescence. Based on the type of vessel disrupted by inflammation (small and/or muscular), the distribution of vasculitis in the dermis and subcutis, and predominate inflammatory cell-type mediating vessel wall damage, a list of relevant differential diagnoses can be generated. This histologic information coupled with extravascular findings such as tissue eosinophilia, tissue neutrophilia, and/or granulomas, plus pathophysiologic markers such as direct immunofluorescent examination for immune complexes and serologic evaluation for antineutrophil cytoplasmic antibodies allows for more accurate diagnosis of specific vasculitic entities. Herein, we review both primary and secondary vasculitic syndromes that affect the skin and show a small vessel neutrophilic mediated vasculitis.

Platelet and soluble CD40L in meningococcal sepsis

OBJECTIVE

To determine the influence of meningococcal sepsis on levels of platelet derived CD40L and on endothelial CD40 expression.

DESIGN AND SETTING

Prospective observational study in two tertiary paediatric intensive care units.

PATIENTS AND PARTICIPANTS

63 children with meningococcal sepsis and 10 age-matched controls.

MEASUREMENTS AND RESULTS

(a) sCD40L ELISA of plasma from patients with meningococcal sepsis (n = 49) and age matched controls (n = 10). This demonstrated higher sCD40L levels in patients (median 0.29 ng/ml, IQR 0.2-0.41) than controls (0.09 ng/ml, 0.08-0.12). However, there was no relationship between plasma sCD40L level and platelet count or disease severity. (b) Flow cytometry of fresh blood from patients with meningococcal sepsis (n = 11) and age-matched controls (n = 10) for membrane bound CD40L and CD62P on circulating platelets. This demonstrated low levels of CD40L and CD62P in patients and controls. CD40L+ platelets were 3.5% (3.0-4.8) in patients and 4.9% (3.5-4.3) in controls. CD62P+ platelets were 10.7% (6.4-12.8) in patients and 7.9% (5.9-13.0) in controls. (c) Immunohistochemistry of skin biopsy specimens from six patients, staining for endothelial CD40 expression at sites of microthrombus formation, which demonstrated preserved CD40 expression in vascular endothelium at sites of microthrombus formation.

CONCLUSIONS

The elevated sCD40L level in meningococcal sepsis implies release of sCD40L from platelets. However, there was no relationship between plasma sCD40L level and the degree of thrombocytopenia or disease severity. Furthermore, platelet surface bound CD40L was similar in controls and patients. Thus, further investigation is needed to determine whether platelet CD40L contributes to inflammation and thrombosis in MCS.

Invasive meningococcal disease presenting as Henoch-Sch�nlein purpura

Henoch-Schonlein purpura (HSP) is an acute systemic form of vasculitis that has been associated with a number of viral and bacterial infections. Described here are the cases of two children with invasive meningococcal disease who presented with clinical and laboratory findings typical of HSP. Meningococcal infection may have been the trigger for the manifestation of HSP in these patients.

High-level endothelial E-selectin (CD62E) cell adhesion molecule expression by a lipopolysaccharide-deficient strain of Neisseria meningitidis despite poor activation of NF-kappaB transcription factor

Binding of host inflammatory cells to the endothelium is a critical contributor to the vascular damage characteristic of severe meningococcal disease and is regulated by endothelial cell adhesion molecules such as ICAM-1, VCAM-1 and CD62E. Intact meningococci induce far higher levels of CD62E than lipopolysaccharide (LPS) alone, whereas LPS is at least as potent as meningococci at inducing both VCAM-1 and ICAM-1 expression. This suggests that meningococci possess additional factors other than LPS present in whole bacteria that result in differential adhesion molecule expression. To investigate this possibility, we studied the capacity of an LPS-deficient isogenic strain of serogroup B Neisseria meningitidis H44/76 (lpxA-) to induce endothelial cell adhesion molecule expression and translocation of the transcription factor NF-kappaB, and compared it to both parent and unencapsulated strains of both B1940 and H44/76 and purified LPS. Although the LPS-deficient isogenic mutant of strain H44/76 was found to be a poor inducer of NF-kappaB, it induced higher levels of CD62E expression than LPS alone. These data provide evidence that intact meningococci induce a range of signals in the endothelium that are distinct from those seen with purified LPS alone and that they occur in a LPS-dependent and LPS-independent manner. These signals may explain the potent effects of N. meningitidis on CD62E expression on vascular endothelium and provide a basis for the complex endothelial dysregulation seen in meningococcal sepsis.

Analysis of pathogen-host cell interactions in purpura fulminans: expression of capsule, type IV pili, and PorA by Neisseria meningitidis in vivo

The pattern of meningococcal surface structure expression in different microenvironments following bloodstream invasion in vivo is not known. We used immunohistochemistry to determine the expression of capsule, type IV pili, and PorA by meningococci residing in the skin lesions of children with purpura fulminans. All the skin biopsy samples showed evidence of thrombosis and, frequently, a perivascular inflammatory cell infiltrate consisting of neutrophils (elastase positive) and monocytes/macrophages (CD68 positive). Modified Gram staining revealed 20 to over 100 gram-negative diplococci in each 4-microm-thick section, usually grouped into microcolonies. Immunoperoxidase staining demonstrated that the invading meningococci expressed PorA, capsule, and type IV pilin. Expression of these antigens was not restricted to any particular environment and was found in association with meningococci located in leukocytes, small blood vessels, and the dermal interstitium. Confocal laser scanning microscopy demonstrated coexpression of pilin and capsule by numerous microcolonies. However, there was some discordance in capsule and pilin expression within the microcolonies, suggesting phase variation. The strategy employed in this study will be helpful in investigating invasive bacterial diseases where antigenic and phase variation has a significant impact on virulence and on vaccine design.

Outer membrane vesicles from Neisseria meningitidis

Flow cytometry was used to study the expression of leukocyte adhesion molecules CD11a, CD11b, CD11c, CD14, and CD62L (L-selectin) and production of reactive oxygen species (ROS) in an ex vivo human whole-blood system stimulated with lipopolysaccharide-containing outer membrane vesicles (LPS-OMV) from N. meningitidis. Results demonstrated a dose-dependent increase in surface expression of CD11a, CD11b, CD11c and CD14 in granulocytes and monocytes (maximal at 30-120 min) upon OMV-LPS challenge, whereas CD62L expression was heavily downregulated (maximal at 30-120 min). The OMV-associated LPS was almost as potent (on a weight basis) as purified LPS from E. coli in inducing adhesion molecule modulation but the response was delayed. Upon stimulation with OMV-LPS or E. coli-LPS, the production of intracellular ROS increased in both granulocytes and monocytes when dihydroethidium (DHE, mainly reflecting superoxide anion) was used as a probe, whereas peroxynitrite production monitored with dihydrorhodamine 123 (DHR) was not significantly changed. The OMV-mediated modulation of leukocyte adhesion molecule expression and increased ROS production may certainly lead to increased entrapment of leukocytes in the microcirculation and contribute to untoward inflammatory reactions as seen in systemic meningococcal disease.

Dysfunction of endothelial protein C activation in severe meningococcal sepsis

BACKGROUND

Impairment of the protein C anticoagulation pathway is critical to the thrombosis associated with sepsis and to the development of purpura fulminans in meningococcemia. We studied the expression of thrombomodulin and the endothelial protein C receptor in the dermal microvasculature of children with severe meningococcemia and purpuric or petechial lesions.

METHODS

We assessed the integrity of the endothelium and the expression of thrombomodulin and the endothelial protein C receptor in biopsy specimens of purpuric lesions from 21 children with meningococcal sepsis (median age, 41 months), as compared with control skin-biopsy specimens.

RESULTS

The expression of endothelial thrombomodulin and of the endothelial protein C receptor was lower in the patients with meningococcal sepsis than in the controls, both in vessels with thrombosis and in vessels without thrombosis. On electron microscopical examination, the endothelial cells were generally intact in both thrombosed and nonthrombosed vessels. Plasma thrombomodulin levels in the children with meningococcal sepsis (median, 6.4 ng per liter) were higher than those in the controls (median, 3.6 ng per liter; P=0.002). Plasma levels, protein C antigen, protein S antigen, and antithrombin antigen were lower than those in the controls. In two patients treated with unactivated protein C concentrate, activated protein C was undetectable at the time of admission, and plasma levels remained low.

CONCLUSIONS

In severe meningococcal sepsis, protein C activation is impaired, a finding consistent with down-regulation of the endothelial thrombomodulin-endothelial protein C receptor pathway.

Leukocytoclastic vasculitis complicating Klebsiella pneumoniae bacteremia

A 79-year old woman, with a history of hypertension, presented with clinical features of congestive heart failure, fever, a purpuric rash, and left lower quadrant abdominal tenderness. Contrast computed tomography scan of the abdomen showed features of acute diverticulitis, and blood culture was subsequently positive for Klebsiella pneumoniae. Histological examination of a biopsy of the rash confirmed a diagnosis of leukocytoclastic vasculitis (LCV). The bacteremia responded to intravenous amoxycillin/clavulanic acid and gentamicin and the rash subsided. This case represents the first case of LCV complicating K. pneumoniae bacteremia in the English literature. The English literature on bacteria-associated LCV is reviewed. Taking aside organisms such as Rickettsia that cause endothelial invasion, the associated bacterial species tends to be subacute or chronic pathogens e.g. Mycoplasma pneumoniae, Mycobacterium tuberculosis, and Yersinia enterocolitica; or the disease process is of a subacute or chronic nature e.g. endocarditis, bronchiectesis, and cystic fibrosis, leading to prolonged exposure to pathogens that apparently cause acute pyogenic infections, such as K. pneumoniae.

Update on meningococcal disease with emphasis on pathogenesis and clinical management

The only natural reservoir of Neisseria meningitidis is the human nasopharyngeal mucosa. Depending on age, climate, country, socioeconomic status, and other factors, approximately 10% of the human population harbors meningococci in the nose. However, invasive disease is relatively rare, as it occurs only when the following conditions are fulfilled: (i) contact with a virulent strain, (ii) colonization by that strain, (iii) penetration of the bacterium through the mucosa, and (iv) survival and eventually outgrowth of the meningococcus in the bloodstream. When the meningococcus has reached the bloodstream and specific antibodies are absent, as is the case for young children or after introduction of a new strain in a population, the ultimate outgrowth depends on the efficacy of the innate immune response. Massive outgrowth leads within 12 h to fulminant meningococcal sepsis (FMS), characterized by high intravascular concentrations of endotoxin that set free high concentrations of proinflammatory mediators. These mediators belonging to the complement system, the contact system, the fibrinolytic system, and the cytokine system induce shock and diffuse intravascular coagulation. FMS can be fatal within 24 h, often before signs of meningitis have developed. In spite of the increasing possibilities for treatment in intensive care units, the mortality rate of FMS is still 30%. When the outgrowth of meningococci in the bloodstream is impeded, seeding of bacteria in the subarachnoidal compartment may lead to overt meningitis within 24 to 36 h. With appropriate antibiotics and good clinical surveillance, the mortality rate of this form of invasive disease is 1 to 2%. The overall mortality rate of meningococcal disease can only be reduced when patients without meningitis, i.e., those who may develop FMS, are recognized early. This means that the fundamental nature of the disease as a meningococcus septicemia deserves more attention.

Update on meningococcal disease with emphasis on pathogenesis and clinical management

The only natural reservoir of Neisseria meningitidis is the human nasopharyngeal mucosa. Depending on age, climate, country, socioeconomic status, and other factors, approximately 10% of the human population harbors meningococci in the nose. However, invasive disease is relatively rare, as it occurs only when the following conditions are fulfilled: (i) contact with a virulent strain, (ii) colonization by that strain, (iii) penetration of the bacterium through the mucosa, and (iv) survival and eventually outgrowth of the meningococcus in the bloodstream. When the meningococcus has reached the bloodstream and specific antibodies are absent, as is the case for young children or after introduction of a new strain in a population, the ultimate outgrowth depends on the efficacy of the innate immune response. Massive outgrowth leads within 12 h to fulminant meningococcal sepsis (FMS), characterized by high intravascular concentrations of endotoxin that set free high concentrations of proinflammatory mediators. These mediators belonging to the complement system, the contact system, the fibrinolytic system, and the cytokine system induce shock and diffuse intravascular coagulation. FMS can be fatal within 24 h, often before signs of meningitis have developed. In spite of the increasing possibilities for treatment in intensive care units, the mortality rate of FMS is still 30%. When the outgrowth of meningococci in the bloodstream is impeded, seeding of bacteria in the subarachnoidal compartment may lead to overt meningitis within 24 to 36 h. With appropriate antibiotics and good clinical surveillance, the mortality rate of this form of invasive disease is 1 to 2%. The overall mortality rate of meningococcal disease can only be reduced when patients without meningitis, i.e., those who may develop FMS, are recognized early. This means that the fundamental nature of the disease as a meningococcus septicemia deserves more attention.

Endothelial adhesion molecule expression and its inhibition by recombinant bactericidal/permeability-increasing protein are influenced by the capsulation and lipooligosaccharide structure of Neisseria meningitidis

Vascular endothelial injury is responsible for many of the clinical manifestations of severe meningococcal disease. Binding and migration of activated host inflammatory cells is a central process in vascular damage. The expression and function of adhesion molecules regulate interactions between leukocytes and endothelial cells. Little is known about how meningococci directly influence these receptors. In this study we have explored the effect of Neisseria meningitidis on endothelial adhesion molecule expression and found this organism to be a potent inducer of the adhesion molecules CD62E, ICAM-1, and VCAM-1. Exposure of endothelium to a serogroup B strain of Neisseria meningitidis, B1940, and a range of isogenic mutants revealed that lipooligosaccharide (LOS) structure and capsulation influence the expression of adhesion molecules. Following only a brief exposure (15 min) to the bacteria, there were large differences in the capacity of the different mutants to induce vascular cell adhesion molecules, with the unencapsulated and truncated LOS strains being most potent (P < 0.05). Furthermore, the pattern of cell adhesion molecule expression was different with purified endotoxin from that with intact bacteria. Meningococci were more potent stimuli of CD62E expression than was endotoxin, whereas endotoxin was at least as effective as meningococci in inducing ICAM-1 and VCAM-1. The effect of bactericidal/permeability increasing protein (rBPI(21)), an antibacterial molecule with antiendotoxin properties, was also dependent on LOS structure. The strains which possessed a truncated or nonsialylated LOS, whether capsulated or not, were more sensitive to the inhibitory effects of rBPI(21). These findings could have important implications for the use of antiendotoxin therapy in meningococcal disease.

Purpura in infants and children

Hemorrhage into the skin (purpura) may result from abnormalities in any of the three components of hemostasis: platelets, plasma coagulation factors, and blood vessels. The morphology, size, and distribution of the hemorrhagic lesions are helpful diagnostic features. The main causes of purpura in the newborn and the more common hemorrhagic disorders in children are reviewed.

Postinfectious purpura fulminans caused by an autoantibody directed against protein S

OBJECTIVE

To determine the mechanism responsible for idiopathic purpura fulminans, we investigated the procoagulant and anticoagulant pathways in five consecutive patients, four after varicella, and the fifth after a nonspecific infection.

METHODS

Procoagulant and anticoagulant factors, including protein C, protein S, and antithrombin III, were measured by quantitative or functional assays. Anti-protein S autoantibodies were identified by dot blotting and Western blotting, and quantified serially by enzyme-linked immunosorbent assay. Clinical and laboratory data were collated retrospectively.

RESULTS

In each case the disease began 7 to 10 days after the onset of the precipitating infection, with rapidly progressive purpura leading to extensive areas of skin necrosis. The illness was complicated by impaired perfusion of limbs or digits (two patients), peripheral gangrene resulting in an above-knee amputation (one patient), and major organ dysfunction caused by thromboembolic phenomena involving the lungs (two patients), the heart (one patient), or the kidneys (one patient). Protein S levels were virtually undetectable at the time of admission and failed to respond to infusions of fresh frozen plasma, despite correction of other procoagulant and anticoagulant factors. All five children had anti-protein S IgM and IgG autoantibodies, which persisted for less than 3 months after admission. Decline in the anti-protein S IgG antibody concentration was associated with normalization of the plasma protein S levels.

CONCLUSIONS

Autoimmune protein S deficiency may be a common mechanism causing postinfectious idiopathic purpura fulminans. Recognition of the pathophysiologic mechanism may provide a rational basis for treatment. Immediate heparinization, infusions of fresh frozen plasma, and, in cases complicated by major vessel thrombosis, the use of tissue-type plasminogen activator may limit thromboembolic complications.

Protein C and protein S levels in two patients with acquired purpura fulminans

Purpura fulminans (PF) is a cutaneous manifestation of a dramatic and deadly syndrome of systemic disseminated intravascular coagulation (DIC). It is characterized by microvascular thrombosis in the dermis followed by perivascular haemorrhage. Since two other related syndromes involve the protein C (PC) system, we undertook a serial study to investigate the levels of PC and protein S (PS) in two patients with acquired PF. Laboratory findings were consistent with DIC, and both patients were treated with blood replacement and heparin therapy. The levels of PC activity were very low during the initial 24-36 h after onset and gradually increased until returning to normal levels. The total and 'free' PS were also abnormal during the initial onset of PF. The total and free PS increased to normal after 4-6 d. Although the pathogenesis is not fully understood, the infection and sepsis appears to consume PC and PS selectively during the PF and DIC phase. Acquired PF appears to selectively involve the PC system in a similar fashion to two other syndromes of PF-like lesions.

Acute meningococcaemia: a case study

A 20-year-old female presented with sudden onset of abdominal pain, diarrhoea and vomiting progressing to fever, tachycardia and mild hypotension. Within 12 hours, a petechial rash appeared on the face and abdomen, spreading to the extremities. Laboratory findings confirmed the diagnosis of acute meningococcaemia. Clinical features of endotoxic shock, vasculitis and skin necrosis rapidly ensued. Aggressive treatment to control the septicaemia, disseminated intravascular coagulation and unstable cardiovascular state ultimately proved successful. Approximately 6 weeks later, amputation of some of the digits and extensive skin grafting were carried out in the Regional Burns Unit. However, serious psychological side effects gradually began to appear which required urgent psychiatric intervention. For an active young woman the challenge of coping with such a severe illness and coming to terms with the disability and disfigurement resulting from it was almost overwhelming. It was, perhaps, particularly hard because of the threat posed to her ambition to complete her nursing education and become a nurse. Little was found in the nursing literature on acute meningococcaemia. But this illness provides considerable challenges not only to those who suffer from it, but also to those who nurse them. A final brief review of published literature on acute meningococcaemia and the clinical manifestations and outcome of it is provided for those who wish to know more about it.

Childhood acute bacterial meningitis in the Sudan: an epidemiological, clinical and laboratory study

The aims of the present study were to document the epidemiology, clinical features and complications of childhood acute bacterial meningitis (ABM) in The Sudan during both an inter-epidemic (endemic) period (1985-1986), and the 1988 serogroup A epidemic; and to examine the phenotypic and genetic similarities and differences of Neisseria meningitidis strains isolated in The Sudan and Sweden. A new enzyme immunoassay test (Pharmacia Meningitis EIA-Test) was evaluated as a potential rapid diagnostic method for the detection of Haemophilus influenzae (HI) type b, Neisseria meningitidis (MC) and Streptococcus pneumoniae (PNC). The test was found to have good sensitivity (0.86) and specificity (0.95) in the inter-epidemic period; and to be adaptable to the field work in The Sudan during the 1988 MC epidemic. During inter-epidemic (endemic) situations in The Sudan, greater than 90% of childhood ABM was caused by one of the three organisms, HI type b, MC and PNC. HI accounted for 57% of the cases. The peak incidence (76%) of HI cases was in infants (less than 12 months) similar to the situation in other African countries. The overall case fatality ratio was 18.6%. Prospective follow-up of survivors for 3-4 years revealed that an additional 43% either died or had permanent neurological complications, the most prevalent and persistent of which was sensorineural hearing loss recorded in 22% of long term survivors. Post-meningitic children were found to have significantly lower intelligence quotients (92.3 +/- 13.9) than their sibling controls (100.7 +/- 10.2, P = 0.029). Features of the large serogroup A sulphonamide resistant MC epidemic (February-August 1988) in Khartoum are described. An estimated annual incidence of 1,679/100,000 was recorded at the peak of the epidemic. The highest attack rate was in young children less than 5 years, as in many other African countries; nevertheless, a high morbidity was observed in adults (31% of the cases greater than or equal to 20 years). The clinical features, mortality (6.3%) and short term sequelae in Sudanese children were generally within the framework described for MC disease elsewhere. Detailed analysis of MC isolates from Sudan and Sweden by characterizing their electrophoretic enzyme types, DNA restriction endonuclease pattern and outer membrane proteins, revealed that serogroup A MC clone III-1 was responsible of The Sudan epidemic in 1988 and has been the dominant serogroup A organism in Sweden since 1973. The Sudanese strains isolated prior to the epidemic (1985) were clone IV-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Skin necrosis secondary to meningococcal septicaemia in an adult

A case of skin loss after meningococcal septicaemia is presented. This is a rare condition in adults and occurs after very severe infections. The skin loss is due to vasculitis, resulting from a combination of direct infection of the skin by Neisseria meningitidis, and an immunological reaction. Secondary infection frequently occurs under the eschar. Skin loss is treated by debridement and delayed split skin grafting.

Meningococcal septicaemia presenting as drug hypersensitivity

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Surgical management of life-threatening and disfiguring sequelae of fulminant meningococcemia

In recent years, because of prompt diagnosis and effective, aggressive resuscitation, the majority of infants and children with fulminant meningococcemia are surviving. From 1974 through 1984, 135 patients with this diagnosis were treated, and 126 of them survived. Although a purpuric skin rash developed in almost all of these patients initially, in eight of them it progressed to multiple confluent areas of cutaneous gangrene, usually associated with extensive necrosis of underlying subcutaneous fat, fascia, skeletal muscle, and even bone. Tissue necrosis seemed to be most extensive in regions of reduced blood flow, such as the extremities, but it almost never followed a pattern of anatomic vascular distribution. A most significant microscopic finding was the presence of multiple fibrin thrombi in vessels, often in close proximity with the foci of tissue necrosis. Five children who ranged in age from 6 months to 12 years required operation. Initially, all surface wounds were treated like full-thickness burns with silver sulfadiazene (Silvadene) dressings. Once the patient's condition had stabilized and the extent of tissue necrosis was apparent, all necrotic tissue was excised and the resulting wounds were temporarily covered with biologic dressings to assure a clean, viable base for skin grafting. Because the resulting quality of life postoperatively in all five surviving patients has been satisfactory, we recommend an aggressive surgical approach in patients with fulminating meningococcemia, despite what may initially appear to be devastating and even lethal complications of this disease.

Rare complications in a case of generalized meningococcal disease: immunologic reaction versus bacterial metastasis

A 14-year-old girl was suffering from meningococcal sepsis with initial endophthalmitis. During a secondary and prolonged fever attack including aseptic meningitis, temporary complications such as pericarditis, arthralgic pains, headache and localized phlebitis were observed. There were three relapses of pericarditis within nine months. Their course was benign. The discussion deals with the pathogenesis of these complications as metastatic and immunologic reactions. The possibility of these complications should be considered during diagnostic investigation and therapeutic treatment.

Fulminant meningococcemia

A case of fulminant meningococcal septicemia is reported in which an acute gastroenteritis was the presenting symptom. Disseminated intravascular coagulation, profound hypotension and a haemorrhagic skin rash were the dominant clinical features. Successful treatment was directed towards the replacement of coagulation factors, treatment of the underlying infection and reversal of hypotension with the inotropic agent, dopamine. Corticosteroids were used in pharmacological doses, but heparin was not used. The pathogenesis of several abnormalities in this disease is briefly reviewed.

Liberation of endotoxin during growth of Neisseria meningitidis in a chemically-defined medium

Modified medium 199 is well suited to the growth of meningococci if rich growth is not necessary. The bacteria were very sensitive to changes in pH and needed a good buffer capacity of the medium. Four strains of Neisseria meningitidis were studied. After the stationary phase had been reached, the vital cell count decreased relatively slowly. However, the total cell count remained unchanged for at least 12 hours. The standardized E. coli endotoxin could be detected easily by the Limulus lysate test in different protein-free, pH-adjusted and ion-balanced liquids, and the determination of endotoxin was reproducible. The Limulus lysate test was more sensitive than the rabbit pyrogen test as regards meningococcal endotoxin. Liberation of endotoxin during growth in modified medium 199 varied with strain and growth conditions. Repeated investigations showed the same pattern of growth and endotoxin liberation for each strain, also under other growth conditions. When sonicating the bacteria, high yields of endotoxin were obtained from each strain.