Calciphylaxis, proteases, and purpura: an alternative hypothesis for the severe shock, rash, and hypocalcemia associated with meningococcal septicemia

Post-genomics of Neisseria meningitidis: an update

Neisseria meningitidis infection still remains a major life-threatening bacterial disease worldwide. The availability of bacterial genomic sequences generated a paradigm shift in microbiological and vaccines sciences, and post-genomics (comparative genomics, functional genomics, proteomics and a combination/evolution of these techniques) played important roles in elucidating bacterial biological complexity and pathogenic traits, at the same time accelerating the development of therapeutic drugs and vaccines. This article summarizes the most recent technological and scientific advances in meningococcal biology and pathogenesis aimed at the development and characterization of vaccines against the pathogenic meningococci.

Mammalian cell transcriptome in response to meningitis-causing pathogens

Bacterial meningitis continues to be a major cause of mortality and morbidity, despite improved antimicrobial therapy. A key factor that contributes to this situation is the incomplete understanding of its pathogenesis. High-throughput methods (e.g., DNA microarray technology) can provide a holistic picture of the transcriptional events that underlie the host response to bacterial infections, including that during bacterial meningitis. Since 2001, several studies have been reported on the cellular host's responses to infections with Neisseria meningitidis and Streptococcus pneumoniae (the leading causes of bacterial meningitis) using DNA microarrays and have described numerous differentially expressed genes. The present review summarizes the main recent findings with gene expression analyses in the field of bacterial meningitis. Experiments that defined a common host response, as well as pathogen-specific host responses, will be discussed. This review will also outline the contributions of global gene analyses to our understanding of the pathophysiology of bacterial meningitis.

Postgenomics of Neisseria meningitidis: an update

Neisseria meningitidis infection represents a major life-threatening bacterial disease worldwide. Genomics has revolutionized every aspect of the field of microbiology. As a consequence of genome sequencing, the postgenomic era commenced 15 years ago. Comparative genomics, functional genomics and proteomics, as well as a combination of these techniques, will play important roles in providing vital information regarding bacterial biological complexity and pathogenic traits, and accelerate the development of therapeutic drugs and vaccines for combating infections. This review summarizes the current knowledge regarding different approaches aimed to shed light on meningococcal biology and pathogenesis, and to accelerate the development and characterization of vaccines against pathogenic meningococci.

Two centuries of meningococcal infection: from Vieusseux to the cellular and molecular basis of disease

Scientific knowledge of meningococcal infection has increased greatly since the epidemic nature of the illness was first described by Vieusseux at the dawn of the nineteenth century. In fact, revolutionary advances have been made in public-health measures, antimicrobial therapy, diagnostic procedures, anti-inflammatory drugs and supportive care facilities. Based on the knowledge accumulated to date, it is generally accepted that the pathogenesis of meningococcal infection involves multiple links that interconnect in a complex web of phenomena from Neisseria meningitidis attachment to meningococcal sepsis or meningitis. In fact, a myriad of strongly interacting inflammatory molecules and cells have been implicated in neisserial infection, illustrating the complexity of meningococcal pathogenesis. In addition, many of these signallers are critically involved in outcomes in the human host. Deciphering the pathogenesis of meningococcal infection could expand our knowledge and provide important clues to the host-pathogen interaction, as well as leading to the development of new therapeutic tools. Herein, we review the history of the discovery and characterization of meningococcal disease, epidemiological features of the disease with an emphasis on recent developments in Brazil, the cellular and molecular basis of disease, and discuss diagnosis and therapy.

Influence of age and foaling on plasma protein electrophoresis and serum amyloid A and their possible role as markers of equine neonatal septicaemia

A field study was undertaken to investigate plasma protein electrophoresis (PPE) and serum amyloid A (SAA) concentrations at 1, 3 and 7 days of age in foals born by oxytocin-induced (group A, n =17) or spontaneous (group B, n =12) parturition. The putative diagnostic role of PPE and SAA in four septicaemic foals was also examined. At birth, beta-gamma-globulins were higher in group B, and then increased in both groups, probably due to colostrum intake. At day 3, no significant differences between the groups were detectable. In both groups, SAA values increased from day 0 to day 3, then decreased at day 7. Septicaemic foals had decreased concentrations of many electrophoretic fractions (probably reflecting decreased colostrum intake and circulating bacterial proteases) and an increased SAA concentration. It was concluded that both PPE and SAA concentrations vary with age and type of foaling and may be useful in the early diagnosis of neonatal septicaemia.

Gene expression pattern in human brain endothelial cells in response to Neisseria meningitidis

To extend our knowledge of target proteins in endothelial cells infected with the meningitis-causing pathogen Neisseria meningitidis, we characterized the interaction between the bacterial and human brain microvascular endothelial cell (HBMEC) monolayers. By use of human cDNA microarrays, transcriptional analysis revealed distinct responses to 4 and 8 h of infection. We also addressed the question of whether the major virulence factor of meningococci, i.e., the capsule, influences the host cell response. Of the 1,493 (at 4 h postinfection) and 1,246 (at 8 h postinfection) genes with altered expression upon bacterial contact, about 49.4% and 45%, respectively, depended on capsule expression. In particular, we identified an increase of expression for genes encoding proteins involved in bacterial adhesion and invasion. High levels of apoptosis-related gene (bad, bak, asp, and immediate-early response gene 1) expression could also be detected in infected cells. Further analyses confirmed that HBMECs displayed several hallmarks of apoptosis in response to N. meningitidis infection, namely, phosphatidylserine translocation and activation of caspase 3 and AMP-activated protein kinase alpha. Moreover, several differentially regulated genes not previously known to respond to meningococcal infection were identified. Of these, genes encoding cell adhesion proteins (CD44, CD98, and CD99), genes involved in downstream signaling of integrins (integrin-linked kinase, mitogen-activated protein kinase kinase 1, and mitogen-activated protein kinase kinase kinase 10) as well as negative regulators of these pathways (dual-specificity phosphatases 1, 5, and 14 and G protein pathway suppressor 2), and genes involved in cytoskeleton reorganization (those encoding Arp2/3, p34-arc, actinin alpha 1, vasodilatator-stimulated protein, and Wiskott-Aldrich syndrome protein) were the most prominent. This global transcriptional analysis creates a new platform for further molecular and cellular analysis of the interaction between N. meningitidis and target cells.

Calciphylaxis--a topical overview

'Calciphylaxis', a calcification syndrome associated with ischaemic cutaneous necrosis, is acquired naturally in humans in disease states. It is a life and limb-threatening complication, usually observed in patients with renal disease and secondary hyperparathyroidism, but known to occur in the absence of renal or parathyroid disease. The reported mortality rate, which ranges from 60-80%, relates to wound infection, sepsis and organ failure. It is a small-vessel vasculopathy, which is estimated to occur in about 4% of haemodialysis patients. Clinically, violaceous, reticulate areas of cutaneous necrosis and eschar may be evident, particularly in the extremities. In addition to the clinical picture, a raised calcium phosphorous product, an elevated parathyroid hormone level, radiographic evidence of vessel and soft-tissue calcification and the finding of mural calcification affecting small arteries and arterioles on histopathology help to confirm the diagnosis of this entity which generally has a poor prognosis. A high index of suspicion and an active multidisciplinary management approach, with rigorous attention to wound care and prevention of sepsis, are vital in the management of these patients. In this overview, we discuss the pathophysiology, clinical features and associations, risk factors, diagnosis and management issues relating to calciphylaxis.

Assessment and management of patients with abnormal calcium

Calcium is essential for homeostasis, and normocalcemia should be maintained strictly during the perioperative period. The biochemistry of calcium equilibrium results from the calcium-sensing receptors on the parathyroid glands, which detect changes in calcium concentrations and initiate the proper response. Asymptomatic hypercalcemia is a common metabolic derangement that is often discovered on routine serum screening. The most common etiologies are primary hyperparathyroidism and cancer. Increasingly, parathyroidectomy is the preferred therapy for primary hyperparathyroidism. Severe hypercalcemia ("hypercalcemic crisis") should be managed aggressively with a combination of intravenous fluids, steroids, bisphosphonates, and calcitonin. Some of these patients may require an urgent parathyroidectomy for calcium control. Hypocalcemia needs to be verified, as many cases of hypocalcemia are the artifact of hypoalbuminemia. Severe hypocalcemia occurs after subtotal or total parathyroidectomy with auto transplantation as well as after massive resuscitation or blood transfusion. Strategies aimed at correcting calcium concentrations depend on the severity of symptomatology. If symptoms are mild, oral calcium supplementation can be given; otherwise, intravenous calcium should be administered.