The European networking for combating meningococcal disease.
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Europe↗
Biomedical subjects
Matthias Frosch
Publications and source records attributed to Matthias Frosch.
A surveillance network for meningococcal disease in Europe.
Between 1999 and 2004, the European Union Invasive Bacterial Infections Surveillance Network (EU-IBIS) received c. 50,000 reports of meningococcal disease from 27 participating countries. Analysis has demonstrated a major decline in the incidence of invasive disease in those countries that have introduced routine vaccination against serogroup C infection. The establishment of rapid reporting of W135 and B2a/B2b strains has been able to provide early reassurance that these strains are not emerging as major public health problems in Europe. Between September 2001 and February 2005, the EU-MenNet project offered further opportunities for enhancing this data resource. Collaborative projects included: improving the EU-IBIS website; reviewing case ascertainment in Europe; reviewing cost-effectiveness studies for meningococcal serogroup C conjugate (MCC) vaccination; international comparisons of MCC vaccine efficacy; and mathematical modelling studies. In addition, linking of data from the European Meningococcal Multi-locus Sequence Type Centre to epidemiological data was performed. Particular clonal complexes were found to be preferentially associated with certain serogroups. Case fatality was also found to vary with clonal complex, suggesting that genotype can be a marker for hypervirulence. The importance of close collaboration between networks of epidemiologists, microbiologists, and the wider scientific and public health community is demonstrated.
Databases, Genetic↗
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.
AMP-Activated Protein Kinases↗
Microarray analyses of meningococcal genome composition and gene regulation: a review of the recent literature.
The development of microarrays for genome comparison and transcriptional profiling along with the public availability of several meningococcal genome sequences has promoted studies elucidating (i) intraspecific and interspecific genomic differences of members of the genus Neisseria, and (ii) the transcriptional response of meningococci to a variety of environmental stresses such as heat shock, iron starvation, serum treatment, and contact with eukaryotic cells. Furthermore, microarray-based finetyping of meningococci is in development. It will remain a difficult, but important, goal to identify sets of genes determining the virulence potential of hypervirulent meningococcal lineages in comparison with apathogenic ones. The recent identification of the meningococcal disease-associated island through the application of microarray analyses has been a step towards this aim. Transcriptional profiling of meningococci has brought about the compilation of large datasets, which also provide information about several regulons. Meningococcal microarray analysis has established a basis for studies clarifying the function of previously unknown genes, and has supported the identification of interesting vaccine candidates. However, harmonization of protocols and tools, as well as central databases are needed to foster the comparability of studies and the integration of knowledge.
Gene Expression Profiling↗
Intracellular survival and replication of Neisseria meningitidis in human brain microvascular endothelial cells.
To cause meningitis the extracellular pathogen Neisseria meningitidis has to traverse the blood-cerebrospinal fluid (B-CSF) barrier. Postulating a transcellular passage, meningococci (MC) have been shown to adhere to and enter B-CSF barrier forming human brain microvascular endothelial cells (HBMEC). Furthermore, electron microscopy studies demonstrated that intracellular MC reside within membrane-bound compartments, both solitary and in groups. To investigate the ability of MC to survive and replicate intracellularly, prolonged gentamicin protection assays were performed. Encapsulated bacteria were found to survive and, after an initial delay, to replicate within HBMEC, whereas the number of intracellular capsule-deficient mutants decreased continuously. This strongly suggests that the capsule plays a pivotal role in the intracellular survival of MC. Further investigations were initiated to characterise the membrane-bound compartment, the Neisseria-containing vacuole (NCV). Immunfluorescence microscopy studies showed that NCVs interact with the endocytic pathway acquiring the early endosomal marker protein, transferrin receptor (TfR), and the late endosomal/lysosomal marker protein Lamp-1.
Brain↗
Evidence for indirect nosocomial transmission of Neisseria meningitidis resulting in two cases of invasive meningococcal disease.
Nosocomial transmission of Neisseria meningitidis has only rarely been reported. Here, we present a significant spatiotemporal association of two cases of invasive meningococcal disease identified by retrospective cluster analysis with the program SaTScan. The most likely epidemiological link was simultaneous hospitalization, resulting in indirect nosocomial transmission.
Adolescent↗
Genetic mechanisms for loss of encapsulation in polysialyltransferase-gene-positive meningococci isolated from healthy carriers.
Encapsulated Neisseria meningitidis expressing serogroups A, B, C, W-135, or Y remain a major cause of morbidity and mortality globally. This bacterium is, however, a common commensal inhabitant of the human nasopharynx that causes disease infrequently. Isolates obtained from healthy carriers are frequently unencapsulated and therefore essentially avirulent. The lack of capsule can be due to inactivation of capsule synthesis genes by a variety of genetic mechanisms, or the absence of capsule synthesis genes. Analysis of inactivation mechanisms was undertaken in a diverse but representative set of 166 acapsulate meningococci isolated from carriage that possessed capsule synthesis genes. Slipped strand mispairing in the siaA and siaD genes of the capsule synthesis locus was observed in 39 isolates. Insertion sequence (IS) elements (IS1016-like, IS1106 and IS1301) were responsible for the loss of encapsulation in 46 isolates. Irreversible gene silencing events (insertions, deletions, base exchanges) were found in 47 isolates. Two non-synonymous mutations were identified in close vicinity of the putative active site of the UDP-N-acetylglucosamine 2-epimerase encoded by the siaA gene. The mechanisms for loss of encapsulation were not associated with particular meningococcal genotypes. There was no evidence for successive gene silencing events in the capsule genes, suggesting that the irreversible inactivation events observed were the result of short-term, within-host evolution. These observations are consistent with the postulate that particular meningococcal clonal complexes are associated with possession of a capsule and that this association is important for transmission success.
Adolescent↗
Identification of Candida fabianii as a cause of lethal septicaemia.
Infections caused by rare fungal species of low pathogenic potential become increasingly common in hospital settings. The identification of these species presents a major challenge for the clinical mycology laboratory. We describe a case of fatal septicaemia caused by Candida fabianii. The use of common biochemical approaches led to misidentification of the isolate as Candida utilis. Sequencing of the internal transcribed spacer regions (ITS1 and ITS2) allowed unequivocal species identification.
Candida↗
Validation of VITEK 2 version 4.01 software for detection, identification, and classification of glycopeptide-resistant enterococci.
We evaluated the ability of the new VITEK 2 version 4.01 software to identify and detect glycopeptide-resistant enterococci compared to that of the reference broth microdilution method and to classify them into the vanA, vanB, vanC1, and vanC2 genotypes. Moreover, the accuracy of antimicrobial susceptibility testing with agents with improved potencies against glycopeptide-resistant enterococci was determined. A total of 121 enterococci were investigated. The new VITEK 2 software was able to identify 114 (94.2%) enterococcal strains correctly to the species level and to classify 119 (98.3%) enterococci correctly to the glycopeptide resistance genotype level. One Enterococcus casseliflavus strain and six Enterococcus faecium vanA strains with low-level resistance to vancomycin were identified with low discrimination, requiring additional tests. One of the vanA strains was misclassified as the vanB type, and one glycopeptide-susceptible E. facium wild type was misclassified as the vanA type. The overall essential agreements for antimicrobial susceptibility testing results were 94.2% for vancomycin, 95.9% for teicoplanin, 100% for quinupristin-dalfopristin and moxifloxacin, and 97.5% for linezolid. The rates of minor errors were 9% for teicoplanin and 5% for the other antibiotic agents. The identification and susceptibility data were produced within 4 h to 6 h 30 min and 8 h 15 min to 12 h 15 min. In conclusion, use of VITEK 2 version 4.01 software appears to be a reliable method for the identification and detection of glycopeptide-resistant enterococci as well as an improvement over the use of the former VITEK 2 database. However, a significant reduction in the detection time would be desirable.
Anti-Bacterial Agents↗
Is serological testing a reliable tool in laboratory diagnosis of syphilis? Meta-analysis of eight external quality control surveys performed by the german infection serology proficiency testing program.
The accuracy of diagnostic tests is critical for successful control of epidemic outbreaks of syphilis. The reliability of syphilis serology in the nonspecialist laboratory has always been questioned, but actual data dealing with this issue are sparse. Here, the results of eight proficiency testing sentinel surveys for diagnostic laboratories in Germany between 2000 and 2003 were analyzed. Screening tests such as Treponema pallidum hemagglutination assay (mean accuracy, 91.4% [qualitative], 75.4% [quantitative]), Treponema pallidum particle agglutination assay (mean accuracy, 98.1% [qualitative], 82.9% [quantitative]), and enzyme-linked immunosorbent assays (ELISAs) (mean qualitative accuracy, 95%) were more reliable than Venereal Disease Research Laboratory (VDRL) testing (mean accuracy, 89.6% [qualitative], 71.1% [quantitative]), the fluorescent treponemal antibody absorption test (FTA-ABS) (mean accuracy, 88% [qualitative], 65.8% [quantitative]), and immunoblot assays (mean qualitative accuracy, 87.3%). Clearly, immunoglobulin M (IgM) tests were more difficult to manage than IgG tests. False-negative results for samples that have been unambiguously determined to be IgM and anti-lipoid antibody positive accounted for 4.7% of results in the IgM ELISA, 6.9% in the VDRL test, 18.5% in the IgM FTA-ABS, and 23.0% in the IgM immunoblot assay. For negative samples, the mean percentage of false-positive results was 4.1% in the VDRL test, 5.4% in the IgM ELISA, 0.7% in the IgM FTA-ABS, and 1.4% in the IgM immunoblot assay. On average, 18.3% of participants misclassified samples from patients with active syphilis as past infection without indicating the need for further treatment. Moreover, 10.2% of laboratories wrongly reported serological evidence for active infection in samples from patients with past syphilis or in sera from seronegative blood donors. Consequently, the continuous participation of laboratories in proficiency testing and further standardization of tests is strongly recommended to achieve better quality of syphilis serology.
Antibodies, Bacterial↗
Subcutaneous Taenia crassiceps infection in a patient with non-Hodgkin's lymphoma.
Infections with larvae of Taenia crassiceps are rare in humans and have mostly affected patients with acquired immunodeficiency syndrome. We report the first case of a patient with malignancy (non-Hodgkin's lymphoma) and infection of the subcutis and muscles of the hand and forearm. Surgery and antiparasitic chemotherapy led to a complete cure.
Aged, 80 and over↗
The molecular mechanisms of larval cestode development: first steps into an unknown world.
Several hundred million years ago, the free-living ancestors of all extant helminth parasites decided to colonize entirely new habitats, the bodies of other metazoan animals. As a consequence of the resulting adaptation processes, they evolved highly complex life-cycles in which many developmental transitions were initiated and controlled by host-derived signals. Understanding the molecular basis of the original developmental mechanisms, and the modifications that occurred during co-evolution with the host, is not only fundamental to our understanding of parasitism but also highly relevant for the design of anti-parasitic drugs and vaccines. In the past several years, molecular investigations on parasitic nematode and trematode development have made considerable progress and, supported by respective genome sequencing projects and emerging methods of genetic manipulation, will be a flourishing field in the years to come. We consider it time that corresponding studies are also pushed for the third large group of parasitic helminths, the cestodes. Here, we review the first experimental steps into that area, which have been undertaken recently. We report on cestode genomics, the identification of signaling factors associated with larval development, and the establishment as well as improvement of in vitro cultivation systems by which cestode life-cycles can be studied in the laboratory.
Animals↗
Genetic analysis of meningococci carried by children and young adults.
BACKGROUND: Neisseria meningitidis is a diverse commensal bacterium that occasionally causes severe invasive disease. The relationship between meningococcal genotype and capsular polysaccharide, the principal virulence factor and vaccine component, was investigated in carried meningococci isolated from 8000 children and young adults in Bavaria, Germany. METHODS: Of the 830 meningococci isolated (carriage rate, 10.4%) by microbiological techniques, 822 were characterized by serogrouping, multilocus sequence typing, and genetic analysis of the capsule region. Statistical and population genetic analyses were applied to these data. RESULTS: The rapid increase in carriage rates with age of carrier, the low prevalence of hyperinvasive meningococci, and the relative prevalence of the 4 disease-associated serogroups were consistent with earlier observations. There was no genetic structuring of the meningococcal population by age of carrier or sampling location; however, there was significant geographic structuring of the meningococci isolated in civil, but not military, institutions. The rate of capsule gene expression did not vary with age of carrier or meningococcal genotype, except for serogroup C, for which increased expression was associated with ST-11 (formerly ET-37) complex meningococci. CONCLUSIONS: Serogroup C capsule expression during carriage may contribute to the invasive character of ST-11 complex meningococci and to the high efficacy of meningococcal serogroup C conjugate polysaccharide vaccine.
Adolescent↗
Lipooligosaccharide of Campylobacter jejuni prevents myelin-specific enteral tolerance to autoimmune neuritis--a potential mechanism in Guillain-Barre syndrome?
Campylobacter jejuni-induced enteritis is the most common infection preceding Guillain-Barre syndrome (GBS), an immune-mediated polyradiculoneuritis. The acute autoimmune attack is thought to be based on C. jejuni antigens which may mimick antigens of the peripheral nervous system. Additional pathomechanisms, like disturbance of natural T cell immunoregulation by C. jejuni, have not been evaluated so far. In experimental autoimmune neuritis (EAN), a T lymphocyte-mediated animal model of human GBS, tolerance to myelin-derived autoantigens can be induced by oral feeding of the respective antigen. Here we investigated whether the lipooligosaccharide (LOS) fraction of C. jejuni may directly alter immunologic tolerance through gastrointestinal pathways. While EAN, actively induced by immunization with bovine peripheral nerve myelin could be ameliorated by precedent feeding of myelin, feeding of C. jejuni LOS along with the myelin antigen not only prevented the tolerizing effects of oral myelin but even accelerated the onset of overt EAN and augmented the myelin-specific B cell response. These findings provide evidence that LOS of C. jejuni, as produced in the gut during C. jejuni-induced enteritis, can disturb natural tolerance to definite proteins which may be or may mimic peripheral nerve antigens. In human patients this may be one of the potential mechanisms to explain why C. jejuni enteritis is a common trigger of GBS.
Animals↗
Evaluation of custom-made DNA microarrays for multilocus sequence typing of Neisseria meningitidis.
Multilocus sequence typing (MLST) has become the gold standard for typing of a variety of bacterial and fungal micro-organisms. Others recently reported the successful use of the tiling DNA array technology to sequence-type Staphylococcus aureus. We now evaluated microarrays based on polymorphism-directed oligonucleotide design for typing of Neisseria meningitidis. The rationale behind this approach was to minimize the number of microarray probes by exploiting the comprehensive knowledge of polymorphisms combined in the Neisseria MLST website. Initial experiments using model oligonucleotides of 28-32 base-pairs in length revealed that the hybridization protocols used were highly specific. However, despite of several optimization steps, the rate of misidentification of oligonucleotides remained > 1.8% in consecutive validation experiments using arrays representing the genetic diversity at three MLST loci. We assume that the high density of polymorphic sites and the extensive GC-content variations at N. meningitidis MLST loci hinder the successful implementation of MLST microarrays based on polymorphism-directed oligonucleotide design.
Alleles↗
Polymorphism of Candida albicans is a major factor in the interaction with human dendritic cells.
Morphological plasticity of Candida albicans is a major virulence factor. Using pH-dependent dimorphism we show, that human dendritic cells (DC) recognize filamentous forms and blastoconidia of a virulent C. albicans isolate (strain SC5314). Heat inactivated and viable blastoconidia are rapidly phagocytosed by human DC. However, viable yeast cells start to filament inside the DC at later stages of infection, leading to penetration and loss of cellular integrity. The cytokine burst of human DC induced upon contact with Candida is dominated by the granulocyte-activating, chemotactic factor IL-8 and the proinflammatory mediator TNF-alpha. Blastoconidia induce markedly lower cytokine levels than filamentous forms. Whereas IL-8 secretion is mainly cell mass dependent, release of TNF-alpha, a major proinflammatory cytokine, is clearly dependent on the morphology of Candida.
Candida albicans↗
Capillary activity of surgical sutures and suture-dependent bacterial transport: a qualitative study.
OBJECTIVE: To evaluate the multitude of new synthetic absorbable sutures (both monofilament and multifilament) in comparison with older materials with regard to capillarity and bacterial transport. METHODS: Sutures of United States Pharmacopoeia (USP) 4-0 thickness were arranged in a three-chamber system under sterile conditions. Either a colorant (liquid transport evaluation) or bacteria (bacterial transport evaluation) were added to the contamination chamber, and movement of colorant or bacteria was evaluated for as long as 30 days. RESULTS: None of the monofilament sutures transported colorant or bacteria. Colorant transport was found on the pseudomonofilament and multifilament sutures between the first and the fifth day. Escherichia coli were transported on the majority of the multifilament sutures, although no transport was found on silk or polyester sutures. Bacterial transport was most often evident in tests using the motile Proteus mirabilis. CONCLUSIONS: All multifilament and pseudomonofilament suture designs allowed transport of colorants and bacteria to some degree. The movement of fluids and bacteria did not depend on the absorptive capacity of the sutures, coating, or the presence of an open suture end.
Capillary Action↗