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W Presber

Publications and source records attributed to W Presber.

At least 37 records · Page 2Linked to original sources
PubMed1998

Mixed infection of human U-937 cells by two different species of Leishmania.

Mixed infections by different Leishmania species could explain differences in the clinical course of these infections. Moreover, mixed infections of the same macrophage could be the basis for parasite recombination. We stained three strains of Leishmania (L. mexicana amazonensis, L. donovani DD8, and L. infantum D2, respectively) with different fluorescent dyes and analyzed them using a fluorescence-activated cell scanner. The simultaneous infection of one cell by Leishmania belonging to two different species was demonstrated. In additional experiments, cells with mixed infections were separated by a fluorescence-activated cell sorter and monitored for 24 hr. Preinfecting human monocytic U-937 cells with one Leishmania species did not exclude a second species added after 3 hr.

Animals↗
PubMed1997

Genotypic and phenotypic determination of five virulence markers in clinical isolates of Escherichia coli.

The presence of the virulence markers K1 capsule, serum resistance, aerobactin, S and P/PR fimbriae were examined in a total of 395 E. coli strains from different extraintestinal infections and in 81 faecal isolates of healthy volunteers using specific DNA probes and classical phenotypic methods. All markers were more frequently detected when genotypic assays were applied. The simultaneous occurrence of 3-4 virulence determinants was typical for isolates derived from patients with septicaemia or meningitis. Isolates from blood cultures and cerebrospinal fluid were expressing the virulence phenotypes to a greater extent than isolates from urine or faeces. The use of colony hybridization with specific oligonucleotide and polynucleotide probes for the detection of virulence determinants has been proven to be more specific and reliable than phenotypic approaches.

Bacterial Capsules↗
PubMed1997

Occurrence of S and F1C/S-related fimbrial determinants and their expression in Escherichia coli strains isolated from extraintestinal infections.

The presence of S and F1C/S-related fimbrial determinants was determined in 462 E. coli strains obtained from different extraintestinal infections and in 162 control isolates of E. coli by using two different DNA probes: an oligonucleotide probe consisting of three oligonucleotides that bind specifically to the S adhesin gene and a polynucleotide probe which is not able to distinguish between S, F1C, and S-related sequences. The expression of S and F1C phenotypes was tested by dot enzyme immunoassay with the corresponding monoclonal antibodies. S fimbriae genotypes were observed more frequently in septic (25%) and urinary (12%) isolates of E. coli than in faecal and water isolates (1%) and often occurred together with O2, O6, O18 and O83 antigens. F1C/S-related fimbrial DNA was detected with a higher frequency in UTI isolates (26%) than in septic (16%) and faecal (10%) isolates and was most frequently associated with O4, O6, and O75 serotypes. Since the production of S and F1C fimbriae was comparatively rare in all clinical and control isolates of E. coli, DNA hybridization assays which allow the sensitive and specific detection of fimbrial determinants even in the absence of their expression are preferable to phenotypic assays.

Adhesins, Escherichia coli↗
PubMed1996

Molecular markers reveal that population structure of the human pathogen Candida albicans exhibits both clonality and recombination.

The life history of Candida albicans presents an enigma: this species is thought to be exclusively asexual, yet strains show extensive phenotypic variation. To address the population genetics of C. albicans, we developed a genetic typing method for codominant single-locus markers by screening randomly amplified DNA for single-strand conformation polymorphisms. DNA fragments amplified by arbitrary primers were initially screened for single-strand conformation polymorphisms and later sequenced using locus-specific primers. A total of 12 single base mutations and insertions were detected from six out of eight PCR fragments. Patterns of sequence-level polymorphism observed for individual strains detected considerable heterozygosity at the DNA sequence level, supporting the view that most C. albicans strains are diploid. Population genetic analyses of 52 natural isolates from Duke University Medical Center provide evidence for both clonality and recombination in C. albicans. Evidence for clonality is supported by the presence of several overrepresented genotypes, as well as by deviation of genotypic frequencies from random (Hardy-Weinberg) expectations. However, tests for nonrandom association of alleles across loci reveal less evidence for linkage disequilibrium than expected for strictly clonal populations. Although C. albicans populations are primarily clonal, evidence for recombination suggests that sexual reproduction or some other form of genetic exchange occurs in this species.

Candida albicans↗
PubMed1996

Identification and determination of the relationships of species and strains within the genus Leishmania using single primers in the polymerase chain reaction.

DNA polymorphisms were assessed in different species and strains within the genus Leishmania by amplifying genomic DNA with single non-specific primers. This polymerase chain reaction (PCR) method employed non-random primers which anneal to mini- and microsatellite DNA sequences like the M13 core sequence and the simple repeat sequences (GTG)5 and (GACA)4, and the T3B primer derived from an intergenic spacer for tRNA genes. Distinctive and reproducible sets of amplified DNA fragments were obtained for all Leishmania isolates tested. The number and size of amplification products were found to be characteristic for a given taxon. Highly similar PCR profiles were observed when genomic DNA of representatives of the L. donovani, L. mexicana or L. braziliensis complexes was amplified. By comparing PCR patterns of unidentified Leishmania isolates with those obtained from reference strains it was possible to identify these isolates at the species level. The information of the amplification patterns was used for the construction of phylogenetic trees to measure the genetic relatedness within the genus Leishmania.

Animals↗
PubMed1996

Rapid identification of Candida species by DNA fingerprinting with PCR.

DNA polymorphisms in different species and strains of the genus Candida were assessed by amplifying genomic DNA with single nonspecific primers. This PCR method employed an arbitrary primer (the 10-mer AP3), a primer derived from the intergenic spacer regions (T3B), and the microsatellite primers (GTG)5 and (AC)10. Distinctive and reproducible sets of amplification products were observed for 26 different Candida and 8 other fungal species. The numbers and sizes of the amplification products were characteristic for each species. All yeast species tested could be clearly distinguished by their amplification patterns. With all primers, PCR fingerprints also displayed intraspecies variability. However, PCR profiles obtained from different strains of the same species were far more similar than those derived from different Candida species. By comparing species-specific PCR fingerprints of clinical isolates with those of reference strains, clinical isolates could be identified to the species level even if they could not be identified by routine biochemical methods.

Base Sequence↗
PubMed1995

Phenotypic and genotypic characterization of unusual vaginal isolates of Candida albicans from Africa.

As expected by its global prevalence, the most frequently isolated species of yeast from vaginal swabs obtained from patients in Africa was Candida albicans, which accounted for 53 of 85 (62.4%) of the isolates from women in Madagascar and 35 of 54 (64.8%) of the culture-positive women in Angola. However, 40% of the Madagascan and 23% of the isolates from Angola, as well as two isolates obtained from one German patient, were not able to utilize the amino sugars glucosamine and N-acetylglucosamine as the sole carbon source. These isolates were able to form germ tubes but did not form chlamydospores. The correct identification as C. albicans was made possible only by using a PCR-based method of DNA fingerprinting. Only minor phenotypic and genotypic variation was observed among these strains. Whether they represent a distinct clone that is found mainly in Africa is not clear. The relevance of the amino sugar catabolic pathway in C. albicans is discussed in view of these results.

Africa↗
PubMed1994

Combined factor and QSAR analysis for antibacterial and pharmacokinetic data from parallel biological measurements.

Antibacterial potency data for a variety of bacterial strains and pharmacokinetic parameters of naphthyridines taken from the literature were submitted to factor and QSAR analyses. Factor analysis of antibacterial potencies unraveled a distinct data structure. The information obtained about the internal relatedness of tests can be used in QSAR analyses and reflects itself in the QSAR results. Factor analysis of pharmacokinetic data also led to a clear grouping of measurements with a strong relationship of half life time and urinary recovery, respectively, with log D.

Animals↗
PubMed1994

[New chemotherapeutics against malarial parasites].

New findings on the molecular biology of plasmodia have led to new approaches for the development of chemotherapeutics. Trials to circumvent the relative toxicity of individual substances by a combination of active agents have been successful in several cases, and there will be more of those combinations in the future. An additional advantage of combinations can be the improvement of activity. In some cases, antiparasitic side effects of long known drugs with low toxicity such as imipramine can be used to decrease or overcome resistance. And, last but not least, ideas or in some cases new drugs will come from the traditional medicine.

Animals↗
PubMed1993

Epidemiological study of an Acinetobacter baumannii outbreak by using polymerase chain reaction fingerprinting.

A polymerase chain reaction (PCR) technique was applied to the fingerprinting of different strains of Acinetobacter baumannii from a cluster of patients infected or colonized with the incriminated pathogen. The DNA was extracted by boiling and was subjected to PCR amplification by using the core sequence of the M13 phase as a single primer. The amplified products were separated by agarose gel electrophoresis and were detected by staining with ethidium bromide. In 1990, 49 multiresistant A. baumannii strains were isolated from 13 patients from the same intensive care unit of the Charité Hospital; 45 of these outbreak isolates obtained from 12 patients showed the same PCR patterns, indicating an epidemiological relatedness of these strains. Four strains isolated from the same patient belonged to another genetic group, as revealed by a distinct amplification pattern. Another single subtype of A. baumannii was identified as the causative agent in patients during a second outbreak at a different intensive care unit in the same hospital. Seventeen isolates recovered from 10 immunocompromised patients had the same amplification patterns, which were distinct from all other PCR profiles. Five strains were obtained from two other hospitals; three isolates from the hospital of Magdeburg, Germany, had identical PCR patterns which, however, could be clearly distinguished from the patterns of all other strains. The remaining two isolates displayed individual patterns of amplified fragments. PCR fingerprinting may provide a useful and particularly rapid identification technique for epidemiological investigations of nosocomial infections.

Acinetobacter↗
PubMed1992

Inhibition of the growth of Plasmodium falciparum and Plasmodium berghei in vitro by an extract of Cochlospermum angolense (Welw.).

An extract of Cochlospermum angolense (Welw.) is used in the traditional medicine of Angola for the therapy of icterus and for the prophylaxis of malaria. From the roots of this plant red crystalline substances have been isolated and tested for their effect on Plasmodium falciparum in vitro and on the DNA and protein synthesis of Plasmodium berghei. The multiplication of P. falciparum was decreased to 50% of the control in the presence of 10 micrograms/ml extracted material and there was a total inhibition at a concentration of 50 micrograms/ml. If mice erythrocytes infected by P. berghei were incubated for 6 h with 25 micrograms/ml of the extract DNA synthesis was depressed to nearly background level. And, even more important, this effect could be demonstrated immediately. On the contrary, protein synthesis continued for at least 90 min at a reduced rate and stopped then. The results obtained show the direct antiparasitic effect of the substances extracted from C. angolense. The activity seems to be directed against DNA synthesis.

Animals↗
PubMed1992

Determination of S fimbriae among Escherichia coli strains from extraintestinal infections by colony hybridization and dot enzyme immunoassay.

449 E. coli strains obtained from septic infections (124 isolates), urinary tract infections (246) and water (79) were surveyed for S/F1C fimbrial DNA by DNA hybridization and for expression of S fimbriae by enzyme immunoassay. S/F1C fimbrial DNA was detected with greater frequency in septic (35%) and urinary (43%) isolates than in water isolates and was often associated with the O2, O4, O6, O18, O83, and O156 serogroups. Most O45 strains did not possess such sequences. Only 12% and 28%, respectively, of the septic and urinary strains possessing S/F1C fimbrial DNA expressed S fimbriae.

Bacteremia↗
PubMed1991

[The effect of an extract from Cochlospermum angolense ("Burututu") on Plasmodium berghei in the mouse malaria suppression test].

Often existing cross-resistance to structure analogous antimalarials causes the need to find new active compounds against malaria parasites. For this purpose the traditional medicine of tropical countries has proved to be a treasury. A root extract of Cochlospermum angolense showed in vitro a remarkable activity against Plasmodium berghei in the DNA synthesis measurement with 3H-labelled hypoxanthine. This effect could be reproduced under in vivo conditions with the "4-day suppressive test" of rodent malaria.

Animals↗
PubMed1990

[Experience and problems with biochemical differentiation of Enterobacteriaceae with microtiter plates].

A self-made miniaturized test system for the biochemical identification of enterobacteriaceae in microtitre plates has been examined. Special emphasis was laid on easy and unequivocal interpretation of the reactions. This was achieved among other things by including further sugar fermentations. Applying a corresponding reaction matrix it is possible to get clear identifications, even in the case of missing test results. The performed tests show the usefulness of our test system.

Bacteriological Techniques↗
PubMed1990

[Viewpoints on preparations for integrating data processing systems in routine microbiology diagnosis].

The enormously risen and further increasing numbers of examinations and tests in microbiological diagnostics within the last years need new methods for treatment. One possibility to meet the higher requirements for information of the clinic without loss in quality at constant staff is the integration of the microcomputer technique into the laboratory as direct "tool". Demands for a qualitatively high empirical antimicrobial chemotherapy, chemotherapy according to antibiotic susceptibility tests, indicated use of antimicrobial drugs and control measures of infectious processes in general are met only by means of a fast information processing. The microcomputer technique in the laboratory provides also the chance to automate still manually performed tests and comprises according to algorithm the strict observation of the diagnostic process and its control. The application of the microcomputer technique on the one hand means for the technical assistant the omission of much manually performed work, on the other hand enables work of higher quality and supports decisions in the diagnostic process. Mathematical and statistical calculations are no longer connected with great losses of activity. The actual need for information of the clinician is met in time in different ways.

Bacteriological Techniques↗
PubMed1990

[Trends in medical microbiology--gene probes in medical microbiology].

At first the principle of nucleic acid hybridisation, some important technics used heretofore, and methods to label nucleic acids are described. The advantages and disadvantages regarding to the application to microbiological diagnostics are discussed. The advantage, before all, is the high specificity of the test which allows to detect the presence and the properties of genes which are not expressed. The methods known up to now can only be applied if the probe is labelled radioactively, since under these conditions the sensitivity is high enough to identify bacteria contained in clinical isolates without prior cultivation. The comparable complex methods are restricted, presently, to special mostly epidemiological problems. To improve these technics regarding increased sensitivity, to the use of non-radioactively labelled probes, to higher speed, and to the automation of the test internationally much work is carried out with great intensity. The solution of these problems will create conditions for a wide application of DNA probes in the general microbiological laboratory.

Bacteria↗