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S Suerbaum

Publications and source records attributed to S Suerbaum.

At least 19 recordsLinked to original sources

[Control of methicillin-resistant S. aureus by active surveillance. Results of a workshop held by the Deutsche Gesellschaft für Hygiene und Mikrobiologie].

In Germany, methicillin-resistant S. aureus (MRSA) is increasing continuously. To control the spread of MRSA, active surveillance and admission screening are recommended. In most cases, screening cultures of patients at risk for MRSA will be sufficient. Screening of all patients admitted to an ICU is cost-effective when the incidence of MRSA and nosocomial MRSA infections is high (>2 cases/100 patients and 0.3 MRSA infections/100 patients, respectively): Under these circumstances, a decrease in the incidence of nosocomial MRSA infections of 50% leads to cost-effectiveness at costs of 16 Euro/sample (including subsequent costs). If the incidence of nosocomial MRSA infections decreases by 75%, costs of 24 Euro/sample (including subsequent costs) are cost-effective. If the incidence of MRSA is high, screening by PCR may be cost-effective for patients at high risk for MRSA, especially if they are isolated prophylactically. Recently, PCR methods have been developed which allow the specific identification of MRSA even from nasal swabs.

Cost-Benefit Analysis↗

[Pathogenesis, diagnostics and treatment of Helicobacter pylori infection].

More than one-half of the world population is infected with Helicobacter pylori. Of those, approx. 500,000 die from gastric carcinoma every year. Ulcer disease, gastricatrophy and the rare MALT lymphoma are other sequelae of H. pylori infection. H. pylori possesses an array of virulence factors that include urease, flagellar motility, adhesins, the vacuolating cytotoxin VacA and the protein CagA. The gene encoding CagA is located on the cag pathogenicity island, comprising 29 genes the majority of which encodes components of a type IV secretion system capable of translocating CagA into epithelial cells where it interferes with cellular signal transduction processes. A number of diagnostic tests for H. pylori infection require gastroendoscopy. These include the biopsy urease test, histology, culture with susceptibility testing, and molecular detection methods such as fluorescent in situ hybridization. Non-invasive tests that do not require endoscopy include the (13)C urea breath test, H. pylori stool antigen ELISA and serology. The latter is unsuitable for treatment follow-up, since antibody titres persist up to a year after successful treatment. When patients have never been treated for H. pylori infection, biopsy urease test and histology are usually sufficient for diagnosis. In patients where endoscopy is not required, H. pylori infection can be reliably detected by (13)C urea breath test, stool antigen ELISA or serology. Patients who have under gone one or more unsuccessful cycles of eradication therapy in most cases harbour H. pylori resistant to one or several antibiotics. In these patients, culture and antibiotic susceptibility testing are indicated. Patients who have never been treated for H. pylori infection usually harbour susceptible strains. In such patients, classic "Italian" or "French" triple therapies may achieve eradication in >90% of cases. In the case of treatment failure, second-line antibiotic treatment regiments (rescue therapy) are used, optimally guided by susceptibility data.

Anti-Bacterial Agents↗

Whipple's disease presenting as an isolated lesion of the cervical spinal cord.

Chronic myelitis from Whipple's disease of the spinal cord is extremely rare. The differential diagnosis includes chronic inflammatory lesions, viral or bacterial infections, and tumours of the spinal cord. Here we present a 50-year-old man with mild sensory deficits because of a large lesion of the cervical spinal cord who markedly showed improvement during probatory antibiotic therapy. PCR and jejunal biopsy were initially negative and only later confirmed the diagnosis of Whipple's disease. Clinical and neuroradiological criteria are suggested which may be of help in the early diagnosis of spinal Whipple's disease before confirmation by molecular biology or histology.

Anti-Bacterial Agents↗

Genetic diversity of intimin genes of attaching and effacing Escherichia coli strains.

In this study, we determined the sequences of four intimin variant genes detected in attaching and effacing Escherichia coli isolates of human origin. Three of them were novel and were designated eae-eta (eta), eae-iota (iota), and eae-kappa (kappa). The fourth was identical to the recently described eae-zeta (zeta), isolated from a bovine E. coli O84:NM isolate. We compared these sequences with those of published intimin-alpha, intimin-beta, intimin-gamma1, intimin-gamma2, intimin- epsilon, and intimin-theta alleles. Sequence analysis of these 10 intimin alleles confirmed extensive genetic diversity within the intimin gene family in E. coli. The genetic diversity was more prominent in the 3' region (starting at bp 2,112), which encodes the binding domain of intimin. Phylogenetic analyses revealed four groups of closely related intimin genes: alpha and zeta; beta and kappa; gamma1 and gamma2/theta; and epsilon and eta. Calculation of homoplasy ratios of sequences of the 5' region of eae (positions 1 to 2,111) revealed evidence for intragenic recombination. Split decomposition analysis also indicates that recombination events have played a role in the evolutionary history of eae. In conclusion, we recommend an eae nomenclature system based on the Greek alphabet and provide an updated PCR scheme for amplification and typing of E. coli eae.

Adhesins, Bacterial↗

Recombination and mutation during long-term gastric colonization by Helicobacter pylori: estimates of clock rates, recombination size, and minimal age.

The bacterium Helicobacter pylori colonizes the gastric mucosa of half of the human population, resulting in chronic gastritis, ulcers, and cancer. We sequenced ten gene fragments from pairs of strains isolated sequentially at a mean interval of 1.8 years from 26 individuals. Several isolates had acquired small mosaic segments from other H. pylori or point mutations. The maximal mutation rate, the import size, and the frequency of recombination were calculated by using a Bayesian model. The calculations indicate that the last common ancestor of H. pylori existed at least 2,500-11,000 years ago. Imported mosaics have a median size of 417 bp, much smaller than for other bacteria, and recombination occurs frequently (60 imports spanning 25,000 bp per genome per year). Thus, the panmictic population structure of H. pylori results from very frequent recombination during mixed colonization by unrelated strains.

Bayes Theorem↗

Experimental Helicobacter pylori infection of rhesus macaques (Macaca mulatta).

The aim of the present study was to establish an animal model for Helicobacter pylori (H. pylori) infection at the German Primate Centre in rhesus monkeys (Macaca mulatta). During the experiments the susceptibility of three animals to different H. pylori strains of human origin was tested. In a follow-up study gastric biopsies from three different sites were investigated in regular intervals using microbiological, histological, electron microscopical and molecular biological methods to evaluate the presence of bacterial colonization and the occurrence of gastritis. It was possible to establish a persistent experimental infection. The rather long follow-up period of 18 months offered the possibility to demonstrate a permanent H. pylori infection in the gastric mucosa of the test animals. The three animals have now been successfully colonized with H. pylori for 18 months and presented a chronic active gastritis confirmed by microbiological and histological methods. By molecular typing, the identity of the isolates recovered from the animals was shown. It was possible to demonstrate that one infection strain outcompeted the second one. Taken together, prerequisites exist for making use of an attractive and useful animal model in rhesus monkeys especially for long term observations.

Animals↗

Allelic diversity and recombination in Campylobacter jejuni.

The allelic diversity and population structure of Campylobacter jejuni were studied by multilocus nucleotide sequence analysis. Sequences from seven housekeeping genes were obtained from 32 C. jejuni isolates isolated from enteritis patients in Germany, Hungary, Thailand, and the United States. Also included was strain NCTC 11168, the complete genomic sequence of which has recently been published. For all loci analyzed, multiple strains carried identical alleles. The frequency of synonymous and nonsynonymous sequence polymorphisms was low. The number of unique alleles per locus ranged from 9 to 15. These alleles occurred in 31 different combinations (sequence types), so that all but two pairs of strains could be distinguished from each other. Sequences were analyzed for evidence of recombination by the homoplasy test and split decomposition. These analyses showed that intraspecific recombination is frequent in C. jejuni and has generated extensive diversity of allelic profiles from a small number of polymorphic nucleotides.

Alleles↗

Genetic diversity of Neisseria lactamica strains from epidemiologically defined carriers.

We assessed the genetic diversity of 26 Neisseria lactamica strains from epidemiologically related sources, i.e., groups of kindergartens and primary schools in three Bavarian towns, by the partial sequencing of the argF, rho, recA, and 16S ribosomal genes. We found a total of 17 genotypes, of which 12 were found only in one strain. The genotypes comprised 5 alleles of the argF gene, 9 of rho, 8 of recA, and 10 of the 16S ribosomal DNA. Sequence analysis by determination of homoplasy ratios and split decomposition analysis revealed abundant recombination within N. lactamica.

Bacterial Proteins↗

Genetic variability within Helicobacter pylori.

One of the striking characteristics of the human gastric pathogen Helicobacter pylori is extensive genetic diversity between different strains. During the last years, intensive research using genomic, molecular genetic and population genetic approaches has permitted to quantitate the diversity in H. pylori, to define its characteristics, and to understand the mechanisms that generate diversity in this global pathogen. This review summarizes the recent developments in this rapidly moving field and discusses the significance of genomic heterogeneity and nucleotide sequence diversity in the contexts of H. pylori epidemiology and pathogenesis.

Genetic Variation↗

The nonfunctional allele TCRBV6S1B is strongly associated with Helicobacter pylori infection.

To determine genetic susceptibility factors for Helicobacter pylori infection, polymorphic T-cell receptor gene elements were investigated in 203 H. pylori-infected individuals and 180 uninfected individuals (controls). H. pylori infection is highly associated with individuals homozygous for the nonfunctional TCRBV6S1B element (odds ratio = 5.9; chi(2) = 13; P = 0.00032; P value corrected for multiple comparisons [Bonferroni correction] = 0. 00063).

Alleles↗

Adherence of isogenic flagellum-negative mutants of Helicobacter pylori and Helicobacter mustelae to human and ferret gastric epithelial cells.

Isogenic flagellum-negative mutants of Helicobacter pylori and Helicobacter mustelae were screened for their ability to adhere to primary human and ferret gastric epithelial cells, respectively. We also evaluated the adherence of an H. pylori strain with a mutation in the flbA gene, a homologue of the flbF/lcrD family of genes known to be involved in the regulation of H. pylori flagellar biosynthesis. H. pylori and H. mustelae mutants deficient in production of FlaA or FlaB and mutants deficient in the production of both FlaA and FlaB showed no reduction in adherence to primary human or ferret gastric epithelial cells compared with the wild-type parental strains. However, adherence of the H. pylori flbA mutant to human gastric cells was significantly reduced compared to the adherence of the wild-type strain. These results show that flagella do not play a direct role in promoting adherence of H. pylori or H. mustelae to gastric epithelial cells. However, genes involved in the regulation of H. pylori flagellar biosynthesis may also regulate the production of an adhesin.

Adhesins, Bacterial↗

Switching of flagellar motility in Helicobacter pylori by reversible length variation of a short homopolymeric sequence repeat in fliP, a gene encoding a basal body protein.

The genome of Helicobacter pylori contains numerous simple nucleotide repeats that have been proposed to have regulatory functions and to compensate for the conspicuous dearth of master regulatory pathways in this highly host-adapted bacterium. H. pylori strain 26695, whose genomic sequence was determined by The Institute for Genomic Research (TIGR), contains a repeat of nine cytidines in the fliP flagellar basal body gene that splits the open reading frame in two parts. In this work, we demonstrate that the 26695(C9) strain with a split fliP gene as sequenced by TIGR was nonflagellated and nonmotile. In contrast, earlier isolates of strain 26695 selected by positive motility testing as well as pig-passaged derivatives of 26695 were all flagellated and highly motile. All of these motile strains had a C(8) repeat and consequently a contiguous fliP reading frame. By screening approximately 50,000 colonies of 26695(C9) for motility in soft agar, a motile revertant with a C(8) repeat could be isolated, proving that the described switch is reversible. The fliP genes of 20 motile clinical H. pylori isolates from different geographic regions possessed intact fliP genes with repeats of eight cytidines or the sequence CCCCACCC in its place. Isogenic fliP mutants of a motile, C(8) repeat isolate of strain 26695 were constructed by allelic exchange mutagenesis and found to be defective in flagellum biogenesis. Mutants produced only small amounts of flagellins, while the transcription of flagellin genes appeared unchanged. These results strongly suggest a unique mechanism regulating motility in H. pylori which relies on slipped-strand mispairing-mediated mutagenesis of fliP.

Amino Acid Sequence↗

Helicobacter pylori infection and polymorphisms in the tumor necrosis factor region.

Twin studies evidence that genetic factors of the host influence the acquisition and the clinical outcome of Helicobacter pylori infections in addition to bacterial and environmental factors. In the tumor necrosis factor (TNF) alpha-gene, allelic frequencies of the polymorphic microsatellite TNFa and the promoter polymorphism TNF-308 were studied for 209 H. pylori+ patients and compared to 184 H. pylori- controls. In the H. pylori+ group 34 individuals suffered from duodenal ulcer and 45 from gastric ulcer. Genotyping of the TNFa microsatellite and TNF-308 polymorphisms was performed after polymerase chain reaction by polyacrylamide gel electrophoresis (PAGE) and allele-specific oligonucleotide hybridizations, respectively. The phenotype frequency of microsatellite allele TNFa6 was lower in the H. pylori+ females as well as infected females with gastric ulcer compared to uninfected controls. Infected men with duodenal ulcer had a decreased frequency of allele TNFa10. The genotype TNF1/TNF1 of the polymorphism TNF-308 is a risk factor for duodenal ulcer in H. pylori+ females; p = 0.01; relative risk (RR) = 10.7; corrected p-value (Pc) = 0.05. Thus, the TNF region is crucial in the complex genetic predisposition for H. pylori infection for certain patient subgroups.

Adolescent↗

Performance of native and recombinant antigens for diagnosis of Helicobacter pylori infection.

The aim of this study was to evaluate the performance of three antigenic preparations for serological diagnosis of Helicobacter pylori infection: (i) native antigens from Helicobacter pylori strain N6 or its aflagellated isogenic mutant N6flbA-, or an acellular extract (antigen AgFA) from a pool of six clinical strains; (ii) recombinant antigens consisting of CagA fused to MS2 polymerase and HspA or recombinant UreA and UreB fused to the maltose-binding protein, and (iii) the preparations provided with two commercial kits, the Cobas Core (Roche Diagnostic Systems, France) and the Pylori Stat (BioWhittaker, Belgium). All preparations were used in an enzyme immunoassay to test 92 sera from dyspeptic patients for whom the status of Helicobacter infection was established. Sensitivities were higher (90 to 100%) for the native antigens and the commercial kits than for the recombinant antigens. Specificities were higher than 90%, except with UreA + UreB (42%). The most useful antigens were those extracted from strains N6 and N6flbA-.

Adolescent↗

Virulence factors of Helicobacter pylori: implications for vaccine development.

Helicobacter pylori is one of the most common infectious diseases in humans and causes gastritis, peptic ulcer disease and malignant tumours of the stomach. This review discusses how H. pylori can colonize the human stomach, an ecological niche that is protected against all other bacteria. Knowledge about the virulence factors of H. pylori has accumulated rapidly over the last decade. Together with the information contained in the complete H. pylori genome sequence, this knowledge is now being applied in the search for a vaccine against this global pathogen.

Animals↗

Recombination and clonal groupings within Helicobacter pylori from different geographical regions.

A collection of 20 strains of Helicobacter pylori from several regions of the world was studied to better understand the population genetic structure and diversity of this species. Sequences of fragments from seven housekeeping genes (atpA, efp, mutY, ppa, trpC, ureI, yphC ) and two virulence-associated genes (cagA, vacA) showed high levels of synonymous sequence variation (mean percentage Ks of 10-27%) and lower levels of non-synonymous variation (mean percentage Ka of 0.2-5.6%). Cluster analysis of pairwise differences between alleles revealed the existence of two weakly clonal groupings, which included half of the strains investigated. All six strains isolated from Japanese and coastal Chinese were assigned to the 'Asian' clonal grouping, probably reflecting descent from a distinct common ancestor. The clonal groupings were not totally uniform; recombination, as measured by the homoplasy test and compatibility matrices, was extremely common within all genes tested, except cagA. The fact that clonal descent could still be discerned despite such frequent recombination possibly reflects founder effects and geographical separation and/or selection for particular alleles of these genes.

Aldose-Ketose Isomerases↗