Biomedical subjects

Ulrich Vogel

Publications and source records attributed to Ulrich Vogel.

At least 37 records · Page 2Linked to original sources

PubMed2005

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↗

PubMed2005

Functional characterization of prostate cancer by integrated magnetic resonance imaging and oxygenation changes during carbogen breathing.

OBJECTIVE: The objective of this study was to evaluate the changes in oxygenation of prostate cancer induced by carbogen breathing using blood oxygen level-dependent (BOLD) magnetic resonance image (MRI) with an endorectal coil (eMRI). MATERIALS AND METHODS: In 32 patients with biopsy-proven prostate cancer, endorectal MRI was performed at 1.5 Tesla using the BOLD method. Images were acquired during 4 x 4-minute episodes alternating between room air and carbogen (95% O2/5% CO2) breathing. In each episode, 40 images were acquired (T2*-weighted EPI sequence, 12-14 slices, 3-mm thickness). All patients underwent radical prostatectomy; BOLD-MRI findings were correlated with the histopathologic results. RESULTS: BOLD-MRI could be evaluated in 29 patients, and revealed heterogeneous signal changes of normal prostate and cancer tissue similar to the heterogeneity of prostate tissue in anatomic/pathologic preparation. A significant signal intensity increase (P = 0.004) was found in normal central gland and peripheral zone during carbogen breathing. Signal enhancement in carcinoma was significantly lower (P = 0.004) compared with the contralateral normal side. CONCLUSION: Intrinsic blood-tissue contrast-functional MRI during carbogen breathing may help detect and characterize prostate carcinoma from normal tissue, particularly in small 1-sided carcinomas. This may be useful for identifying candidates for radiotherapy and monitoring noninvasive therapeutic approaches.

Aged↗

PubMed2005

Carbohydrate composition of meningococcal lipopolysaccharide modulates the interaction of Neisseria meningitidis with human dendritic cells.

Meningococcal lipopolysaccharide (LPS) is of crucial importance for the pathogenesis of invasive infection. We show that sialylation and elongation of the alpha-chain effectively shields viable unencapsulated Neisseria meningitidis from recognition by human dendritic cells (DC). In contrast, beta- and gamma- chain of the LPS carbohydrate moiety play only a minor role in the interaction with DC. The protective function of the LPS for the bacteria can be counteracted in vivo by phase variation of the lgtA gene encoding LPS glycosyltransferase A. Capsule expression protects N. meningitidis efficiently from recognition and phagocytosis by DC independent of the LPS structure. Despite the significant impact of LPS composition on the adhesion and phagocytosis of N. meningitidis no differences were found in terms of cytokine levels secreted by DC for IL1-beta, IL-6, IL-8, TNF-alpha, IFN-gamma and GM-CSF. However, significantly lower levels of the regulatory mediator IL-10 were induced by encapsulated strains in comparison to isogenic unencapsulated derivatives. IL-10 secretion was shown to depend on phagocytosis because poly alpha-2,8 sialic acid did not influence IL-10 secretion. The use of truncated LPS isoforms in vaccine preparations can therefore not only result in attenuation but also in more efficient targeting of DC.

Bacterial Capsules↗

PubMed2005

Interlaboratory comparison of PCR-based identification and genogrouping of Neisseria meningitidis.

Twenty clinical samples (18 cerebrospinal fluid samples and 2 articular fluid samples) were sent to 11 meningococcus reference centers located in 11 different countries. Ten of these laboratories are participating in the EU-MenNet program (a European Union-funded program) and are members of the European Monitoring Group on Meningococci. The remaining laboratory was located in Burkina Faso. Neisseria meningitidis was sought by detecting several meningococcus-specific genes (crgA, ctrA, 16S rRNA, and porA). The PCR-based nonculture method for the detection of N. meningitidis gave similar results between participants with a mean sensitivity and specificity of 89.7 and 92.7%, respectively. Most of the laboratories also performed genogrouping assays (siaD and mynB/sacC). The performance of genogrouping was more variable between laboratories, with a mean sensitivity of 72.7%. Genogroup B gave the best correlation between participants, as all laboratories routinely perform this PCR. The results for genogroups A and W135 were less similar between the eight participating laboratories that performed these PCRs.

Adolescent↗

PubMed2004

Emergency donor heart protection: application of the port access catheter technique using a pig heart transplantation model.

BACKGROUND: Organ shortage limits the number of transplantations, and donor deterioration may precede and often prevent conventional organ preservation. This study evaluates in situ perfusion as a bedside method for cardiac allograft procurement in a large animal model. METHODS: Thirty Landrace pigs (42 +/- 7 kg) were studied. The hearts in the conventional group underwent cardioplegic arrest with University of Wisconsin solution and sodium-hydrogen exchange inhibitor cariporide as an additive; they were explanted and stored on ice before transplantation. In the in situ group, one catheter was placed in the ascending aorta and another in the right atrium. After disconnection from the ventilator, hypoxia caused circulatory arrest. The aorta was endoclamped, and in situ perfusion of the aortic root was maintained with University of Wisconsin solution and cariporide. After explantation, hearts were stored on ice for 120 min. All hearts were implanted according to the Shumway technique. Ventricular pressure and cardiac output were monitored online, and troponin-I was measured intermittently. Two hours after weaning from extracorporal circulation, the animals were killed and histology was performed. RESULTS: Catheters were placed through introducers within 5 min. Functional recovery and histology were comparable between the two techniques. Troponin-I increased in both groups during reperfusion but at a faster rate in the in situ technique (P <0.01). CONCLUSION: In situ perfusion may be suitable for cardiac transplants when donor deterioration requires urgent organ preservation. Catheters can be placed at bedside and modified to achieve multi-organ protection through additional perfusion of the abdominal aorta.

Adenosine↗

PubMed2004

PET with [18F]fluorothymidine for imaging of primary breast cancer: a pilot study.

The aim of this study was to evaluate the use of [(18)F]fluorothymidine (FLT) as a positron emission tomography (PET) tracer for the diagnosis of breast cancer. To this end, 12 patients with 14 primary breast cancer lesions (T2-T4) were studied by FLT-PET. For comparison, [(18)F]fluorodeoxyglucose (FDG) PET scans were performed in six patients. Thirteen of the 14 primary tumours demonstrated focally increased FLT uptake (SUV(mean)=3.4+/-1.1). Seven out of eight patients with histologically proven axillary lymph node metastases showed focally increased FLT uptake in the corresponding areas (SUV(mean)=2.4+/-1.2). The lowest SUV (mean =0.7) was observed in one of two inflammatory cancers. The contrast between primary tumours or metastases and surrounding tissue was high in most cases. In direct comparison to FDG-PET, the SUVs of primary tumours (5/6) and axillary lymph node metastases (3/4) were lower in FLT-PET (SUV(FLT): 3.2 vs SUV(FDG): 4.7 in primary tumours and SUV(FLT): 2.9 vs SUV(FDG): 4.6 in lymph node metastases). Since FLT uptake in surrounding breast tissue was also lower, tumour contrast was comparable to that with FDG. It is of note that normal FLT uptake was very low in the mediastinum, resulting in a higher tumour-to-mediastinum ratio as compared to FDG ( P=0.03). FLT-PET is suitable for the diagnosis of primary breast cancer and locoregional metastases. High image contrast may facilitate the detection of small foci, especially in the mediastinum.

Adult↗

PubMed2004

Genetic lineages and their traits in Neisseria meningitidis.

Neisseria meningitidis is a model organism for the study of bacterial population biology, for genome sequencing and pathogenicity research. In the recent years, our group has identified a variety of markers for hypervirulent lineages of meningococci, which in part could be validated for typing purposes. Furthermore, carrier strain collections of meningococci and N. lactamica were studied by multilocus sequence typing, and elucidated the impressive genetic variability of those species. Characterisation of meningococcal carrier strains allowed to define the capsule null locus (cnl) of meningococci, which frequently occurs among carrier isolates and renders strains constitutively unencapsulated. This finding poses the question about the yet unclear role of the meningococcal polysaccharide capsule in transmission and carriage. O-acetylation of the meningococcal polysaccharides is another variably expressed trait in meningococci. We identified the genes responsible for O-acetylation of the serogroup C, W-135 and Y capsules, and provided the genetic basis for understanding the variability of O-acetylation patterns in meningococci. The oatC and oatWY genes proved to be the first genes identified to be responsible for O-acetylation of polysialic acid.

Acetylation↗

PubMed2004

Genetics of capsule O-acetylation in serogroup C, W-135 and Y meningococci.

Capsular polysaccharides of serogroup C, W-135 and Y meningococci were previously reported to be O-acetylated at the sialic acid residues. There is evidence that O-acetylation affects the immunogenicity of polysaccharide vaccines. We identified genes indispensable for O-acetylation of serogroup C, W-135 and Y meningococci downstream of the capsule synthesis genes siaA-D. The genes were co-transcribed with the sia operon as shown by reverse transcription polymerase chain reaction analysis. The putative capsular polysaccharide O-acetyltransferases were designated OatC and OatWY. The protein OatWY of serogroups W-135 and Y showed sequence homologies to members of the NodL-LacA-CysE family of bacterial acetyltransferases, whereas no sequence homology with any known protein in the different databases was found for the serogroup C protein OatC. In serogroup W-135 and Y meningococci, several clonal lineages either lacked OatWY or OatWY was inactivated by insertion of IS1301. For serogroup C meningococci, we observed in vitro phase variation of O-acetylation, which resulted from slipped-strand mispairing in homopolymeric tracts. This finding explains the observation of naturally occurring de-O-acetylated serogroup C meningococci. Our report is the first description of sequences of sialic acid O-acetyltransferase genes that have not been cloned from either other bacterial or mammalian organisms.

Acetylation↗

PubMed2004

Bacteremia in an immunocompromised patient caused by a commensal Neisseria meningitidis strain harboring the capsule null locus (cnl).

We recently described the capsule null locus (cnl) of constitutively unencapsulated Neisseria meningitidis clonal lineages. cnl meningococci were recovered from healthy carriers at high frequency. We here report on the first case of invasive disease caused by cnl meningococci in a severely immunosuppressed patient with chronic graft-versus-host disease after allogeneic peripheral blood stem cell transplantation. The sequence type 845 strain was extensively typed and, furthermore, shown to be sensitive to serum bactericidal activity.

Adult↗

PubMed2003

Neisserial lipooligosaccharide is a target for complement component C4b. Inner core phosphoethanolamine residues define C4b linkage specificity.

We identified Neisseria meningitidis lipooligosaccharide (LOS) as an acceptor for complement component C4b (C4b). Phosphoethanolamine (PEA) residues on the second heptose (HepII) residue in the LOS core structure formed amide linkages with C4b. PEA at the 6-position of HepII (6-PEA) was more efficient than 3-PEA in binding C4b. Strains bearing 6-PEA bound more C4b than strains with 3-PEA and were more susceptible to complement-mediated killing in serum bactericidal assays. Deleting 3-PEA from a strain that expressed both 3- and 6-PEA simultaneously on HepII did not decrease C4b binding. Glycose chain extension of the first heptose residue (HepI) influenced the nature of the C4b-LOS linkage. Predominantly ester C4b-LOS bonds were seen when lacto-N-neotetraose formed the terminus of the glycose chain extension of HepI with 3-PEA on HepII in the LOS core. Related LOS species with more truncated chain extensions from HepI bound C4b via amide linkages to 3-PEA on HepII. However, 6-PEA in the LOS core bound C4b even when the glycose chain from HepI bore lacto-N-neotetraose at the terminus. The C4A isoform exclusively formed amide linkages, whereas C4B bound meningococci preferentially via ester linkages. These data may serve to explain the preponderance of 3-PEA-bearing meningococci among clinical isolates, because 6-PEA enhances C4b binding that may facilitate clearance of 6-PEA-bearing strains resulting from enhanced serum killing by the classical pathway of complement.

Amides↗

PubMed2003

Molecular epidemiology of Neisseria meningitidis.

Neisseria meningitidis poses a major disease burden on human beings. Meningococcal typing has a longstanding tradition for epidemiological surveillance of the disease. Genetic and antigenetic variability resulting from horizontal genetic exchange has been exploited for this purpose. Neisseria meningitidis served as the bacterial prototype organism for the development of multi locus sequence typing, which has replaced multi locus enzyme electrophoresis as the gold standard for meningococcal typing. Due to the rapid emergence of new porin variants serotyping by monoclonal antibodies is currently being replaced by DNA sequencing of variable regions of the porA gene. Sequence data were used to characterize the population structure of meningococci in carriage and disease. The advances in molecular epidemiology of meningococcal disease, and the rapid exchange of DNA sequence data via curated internet websites have resulted in an interactive international network, which is capable of identifying newly emerging clones within weeks.

Humans↗

PubMed2003

Sodium-hydrogen inhibitor cariporide (HOE 642) improves in situ protection of hearts from non-heart-beating donors.

BACKGROUND: Reperfusion injury is a vital problem in non-heart-beating donor (NHBD) organs. The sodium-hydrogen inhibitor cariporide is thought to improve cellular integrity after ischemia and reperfusion. Recently, we demonstrated the possibility of preserving hearts with in situ perfusion after circulatory death. The purpose of this study was to determine whether cariporide improves in situ heart protection. METHODS: We studied 20 pigs (18 +/- 2 kg). Hearts in the conventional group (CON, n = 6) underwent cardioplegic arrest with University of Wisconsin solution and then were explanted and stored for 150 minutes on ice. In the other groups, a catheter was placed in each ascending aorta and right atrium. After disconnecting the ventilator, hypoxia caused circulatory arrest within 7 +/- 2 minutes. The aorta was endoclamped, and continuous in situ perfusion of the aortic root was maintained for 60 minutes with University of Wisconsin solution (UW, n = 7) or with UW solution and cariporide (CAR, n = 7). After explantation, the hearts were stored on ice for 90 minutes. In all groups, hearts were reperfused with homologous, whole pig blood in an isolated working heart model for 45 minutes. We monitored stroke-work index on-line, intermittently measured troponin I and malondialdehyde, and compared light microscopic examinations among the groups. RESULTS: Stroke-work index was higher in the CAR group compared with the UW group during the last 20 minutes of reperfusion (10(3)dynes x cm x beats(-1)x gm(-1), 6.6 +/- 1.4 vs 4.5 +/- 2.0, p < 0.05), troponin I was lower in the CAR group compared with the UW group (161 +/- 32 ng/ml vs 277 +/- 35 ng/ml, p < 0.05). Results of malondialdehyde and light microscopic examinations were slightly better in the CAR group, without reaching statistical significance. CONCLUSION: Cariporide as an additive to UW solution improves functional recovery and decreases myocardial damage in hearts from NHBDs protected with an in situ perfusion technique.

Adenosine↗

PubMed2003

Molecular analysis of bacteria in periodontitis: evaluation of clone libraries, novel phylotypes and putative pathogens.

Subgingival plaque samples were obtained from 26 subjects with advanced periodontal lesions. Bacterial diversity was analysed by amplification of the 16S rRNA genes with two different primer sets, and subsequent cloning and sequencing. A total of 578 sequences was analysed after the exclusion of chimeras. The authors found 148 phylotypes with the clone library 27f/519r (number of clones n=322; coverage, C=66 %) and 75 phylotypes with the clone library 515f/1525r (n=256; C=84 %). Comparative sequence analysis revealed that 70 % of all of the analysed sequences showed a similarity of at least 99 % to sequences deposited in public databases. The classes Actinobacteria, Bacilli, Bacteroidetes, Clostridia, Deferribacteres, Flavobacteria, Fusobacteria, Mollicutes, Spirochaetes and all classes of the Proteobacteria were represented. Sequences that were at least 99 % identical to Porphyromonas gingivalis, Filifactor alocis and Treponema socranskii were present in at least one-third of the patients. Libraries generated with the two PCR primer pairs differed significantly in their representation of the families Porphyromonadaceae, Prevotellaceae, Fusobacteriaceae, Eubacteriaceae, Streptococcaceae and ACIDAMINOCOCCACEAE: A total of 14 sequences exhibited less than 97 % identity to sequences published previously and were assigned to six different families within the phyla Bacteroidetes and FIRMICUTES: Twelve of 20 putative pathogens were recovered, which were recently proposed to be associated with periodontitis.

Adult↗

PubMed2003

Typing of methicillin-resistant Staphylococcus aureus in a university hospital setting by using novel software for spa repeat determination and database management.

The spa gene of Staphylococcus aureus encodes protein A and is used for typing of methicillin-resistant Staphylococcus aureus (MRSA). We used sequence typing of the spa gene repeat region to study the epidemiology of MRSA at a German university hospital. One hundred seven and 84 strains were studied during two periods of 10 and 4 months, respectively. Repeats and spa types were determined by Ridom StaphType, a novel software tool allowing rapid repeat determination, data management and retrieval, and Internet-based assignment of new spa types following automatic quality control of DNA sequence chromatograms. Isolates representative of the most abundant spa types were subjected to multilocus sequence typing and pulsed-field gel electrophoresis. One of two predominant spa types was replaced by a clonally related variant in the second study period. Ten unique spa types, which were equally distributed in both study periods, were recovered. The data show a rapid dynamics of clone circulation in a university hospital setting. spa typing was valuable for tracking of epidemic isolates. The data show that disproval of epidemiologically suggested transmissions of MRSA is one of the main objectives of spa typing in departments with a high incidence of MRSA.

Germany↗

PubMed2003

Identification of the hypervirulent lineages of Neisseria meningitidis, the ST-8 and ST-11 complexes, by using monoclonal antibodies specific to NmeDI.

Most cases of serogroup C meningococcal disease are caused by the clonal lineages ST-8 and ST-11. The gene encoding the putative restriction-modification system NmeDI is specific to these lineages. We report here a monoclonal antibody directed against the NmeDI endonuclease as a tool for their rapid and spe-cific identification.

Antibodies, Monoclonal↗

PubMed2002

O-Acetylation status of the capsular polysaccharides of serogroup Y and W135 meningococci isolated in the UK.

At a time when tetravalent conjugate vaccines for meningococcal serogroups A/C/Y/W135 are being formulated the O-acetylation status of their respective capsular polysaccharides has not previously been studied in the UK for all components. Although this has been elucidated for serogroup C, little is known about the O-acetylation status of serogroups W135 and Y. Meningococcal serogroup W135 (n=181) and Y (n=90) isolates submitted to the PHLS Meningococcal Reference Unit in 1996, 2000 and 2001 were investigated for O-acetylation capsular status by dot blot assay. Eight per cent of W135 and 79% of Y isolates respectively were found to be O-acetylated with a similar distribution found in both carrier and case isolates. An increase in O-acetylated W135 isolates was noted between 2000 (0%) and 2001 (21%) which was not due to the introduction of the Hajj associated W135 (ET 37 complex; serosubtype P1.5,2) isolates, all of which were de-O-acetylated. Although the biological relevance of O-acetylation status is unknown for these serogroups, an understanding of O-acetylation status of the respective polysaccharides may provide useful insights into the optimal vaccine formulation.

Acetylation↗

PubMed2002

Diagnostic potential of targeted electrical impedance scanning in classifying suspicious breast lesions.

RATIONALE AND OBJECTIVE: To evaluate the potential of targeted electrical impedance scanning (EIS) for classifying suspicious breast lesions. METHODS: EIS was performed in full knowledge of mammographic findings and findings of clinical breast examination. One hundred seventeen patients with a total of 129 breast lesions were examined with EIS before breast biopsy (surgical excision or vacuum core biopsy). Diagnostic indexes of targeted EIS were calculated depending on major lesion characteristics. Capacitance and conductivity of all positive spots (S) and the surrounding normal breast tissue (NBT) were quantified using ROI measurements. The ratio S/NBT was calculated to compare true positive (n = 44) and false positive (n = 18) spots. RESULTS: With respect to histology, of the 129 lesions 71 were malignant and 58 lesions were benign. Overall sensitivity of targeted EIS was 62%, specificity 69%, PPV 71%, and NPV 60%. Sensitivity of EIS varied depending on the tumor size, which was between 48% (> 20 mm) and 71% (11-20 mm). Highest specificity (86%) was observed for large lesions (> 20 mm); however, the NPV was only 35% for lesions of that size. NPV was higher for nonpalpable lesions (74%) and clusters of microcalcifications (85.7%) compared with palpable lesions (39%) and solid lesions (44%). There was no statistical difference of S/NBT ratio neither for conductivity nor capacitance of true and false positive spots. Compared with true positive spots a trend of a higher conductivity ratio at 100 Hz and 200 Hz was seen for false positive spots. CONCLUSION: EIS showed mediocre overall diagnostic accuracy for classifying suspicious breast lesions. Quantitative analysis of positive EIS findings did not help to differentiate between false and true positive spots.

Biopsy↗

PubMed2002

Many carried meningococci lack the genes required for capsule synthesis and transport.

Of 830 Neisseria meningitidis isolates obtained from healthy carriers in Bavaria, Germany, 136 (16.4%) lacked the operons necessary for the synthesis, lipid modification, and transport of capsular polysaccharide. These operons were replaced by a non-coding intergenic region either 113 or 114 bp in length, termed here the capsule null locus (cnl). Comparisons of the nucleotide sequence of this region in the meningococcus and its acapsulate relatives, Neisseria gonorrhoeae and Neisseria lactamica, revealed six distinct sequence variants (cnl-1 to cnl-6), with a total of 10 nucleotide substitutions and three indels. With the exception of one 4 bp insertion, which was unique to a gonococcal isolate, all of the individual sequence changes were present in the N. lactamica isolates examined. The meningococcal isolates with a cnl belonged to one of four otherwise genetically diverse genetic groupings: the ST-53 and ST-1117 complexes (75 isolates); the ST-845 complex (12 isolates); the ST-198 and 1136 complexes (46 isolates), and the ST-44 complex (one isolate). These data demonstrated that a substantial proportion of carried meningococci were incapable of capsule production, that the cnl circulated within Neisseria populations by horizontal genetic exchange, and that the expression of a polysaccharide capsule was not a requirement for person-to-person transmission of certain meningococcal lineages.

Bacterial Capsules↗