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Biomedical subjects

N Weiss

Publications and source records attributed to N Weiss.

At least 55 records · Page 3Linked to original sources
PubMed1998

Aureobacterium resistens sp. nov., exhibiting vancomycin resistance and teicoplanin susceptibility.

Two similar strains of a coryneform bacterium were isolated from human clinical material. Both strains were resistant to vancomycin but susceptible to teicoplanin. Detailed biochemical, chemotaxonomical, and molecular genetic investigations revealed that both isolates were members of a hitherto undescribed species of genus Aureobacterium. The name Aureobacterium resistens sp. nov. is proposed for the new bacterium and the type strain is CCUG 38312.

Adult↗
PubMed1998

Dehalobacter restrictus gen. nov. and sp. nov., a strictly anaerobic bacterium that reductively dechlorinates tetra- and trichloroethene in an anaerobic respiration.

The highly enriched anaerobic bacterium that couples the reductive dechlorination of tetrachloroethene to growth, previously referred to as PER-K23, was obtained in pure culture and characterized. The bacterium, which does not form spores, is a small, gram-negative rod with one lateral flagellum. It utilized only H2 as an electron donor and tetrachloroethene and trichloroethene as electron acceptors in an anaerobic respiration process; it could not grow fermentatively. Acetate served as a carbon source in a defined medium containing iron as the sole trace element, the two vitamins thiamine and cyanocobalamin, and the three amino acids arginine, histidine, and threonine. The cells contained menaquinones and b-type cytochromes. The G+C content of the DNA was 45.3 +/- 0.3 mol%. The cell wall consisted of type-A3gamma peptidoglycan with ll-diaminopimelic acid and one glycine as an interpeptide bridge. The cells are surrounded by an S-layer; an outer membrane was absent. Comparative sequence analysis of the 16S rRNA sequence showed that PER-K23 is related to gram-positive bacteria with a low G+C content of the DNA. Based on the cytological, physiological, and phylogenetic characterization, it is proposed to affiliate the isolate to a new genus, Dehalobacter, with PER-K23 as the type strain of the new species Dehalobacter restrictus.

Anaerobiosis↗
PubMed1998

Ganciclovir and foscarnet efficacy in AIDS-related CMV polyradiculopathy.

Cytomegalovirus (CMV) polyradiculopathy is a rare complication of AIDS in which ascending motor weakness, sensory loss and urinary retention are associated with polymorphonuclear pleocytosis and positive CMV polymerase chain reaction in the cerebrospinal fluid (CSF). We describe three patients with this syndrome. One patient's paresis improved after ganciclovir therapy. Another patient deteriorated despite foscarnet treatment, but improved after ganciclovir was added. The third patient died from ascending paralysis despite ganciclovir-foscarnet combination. Reviewing the literature, we conclude that antiviral treatment reduced mortality from 100 to 22%. In patients with ascending paralysis treatment, failure may be caused by viral drug resistance, at least in some patients. Risk factors for treatment failure are preceding monotherapy for other CMV diseases or persistent CSF pleocytosis on serial CSF analysis. We suggest that these patients should therefore be treated with the alternative drug or a ganciclovir-foscarnet combination therapy.

AIDS-Related Opportunistic Infections↗
PubMed1998

Diagnostics in onchocerciasis: future challenges.

The classical method of determining the prevalence and intensity of onchocercal infection is by the demonstration and counting of microfilariae in biopsies obtained by skin snipping. Although very specific, this technique is inadequate for detecting early, light or prepatent infections, and is also becoming increasingly unacceptable to the populations investigated. The prolonged clearing effect that Mectizan (ivermectin, MSD) treatment has on skin microfilariae also renders the skin-snip method of diagnosis less appropriate in areas with Mectizan treatment. Given all these factors, the greater challenge in the area of diagnostics for onchocerciasis is to develop a less invasive, adequately sensitive, and equally specific diagnostic test, either to replace or to be an adjunct to the present skin-snip method. This challenge is being addressed, with at least three new diagnostic tests for onchocerciasis under development: an immunological assay, based on a three-antigen cocktail; a PCR-based assay, which may also be used for 'pool screening' of blackflies; and the diethylcarbamazine (DEC) patch test. Of all these tests, the DEC patch test seems to fit best the criteria of an ideal test. The PCR assay would be better than the patch test if the cost of using it could be reduced substantially.

Animals↗
PubMed1997

The ICT Filariasis Test: A rapid-format antigen test for diagnosis of bancroftian filariasis.

Antigen testing is now recognized as the method of choice for detection of Wuchereria bancrofti infections. Unlike tests that detect microfilariae, antigen tests can be performed with blood collected during the day or night. However, existing enzyme-linked immunosorbent assay (ELISA) tests for filarial antigenemia are difficult to perform in the field, and this has limited their use in endemic countries. In this article, Gary Weil, Patrick Lammie and Niggi Weiss review their experience with a new rapid-format filarial antigen test. They found that the ICT card test was very easy to perform and that it was comparable with ELISA for the detection of filarial antigen in sera from people with microfilaremia. The introduction now of an antigen test suitable for use in the field is especially timely, in that it may facilitate implementation of new strategies proposed by the World Health Organization for control and elimination of lymphatic filariasis.

Journal Article↗
PubMed1997

The diverse expression of immunity in humans at distinct states of Onchocerca volvulus infection.

This study examined the development and persistence of immunity in humans presenting defined states of Onchocerca volvulus infection, i.e. in exposed endemic control individuals without microfilaridermia and clinical disease, in patients with patent or post-patent onchocerciasis, and in patients concurrently infected with Mansonella perstans. Onchocerca volvulus antigen (OvAg)-specific cellular reactivity was significantly diminished in microfilariae (mf)-positive patients, while the highest reactivity was measured in exposed but mf-negative endemic controls, those being free of any clinical signs of onchocercal disease. In patients who became post-patent, responses to OvAg were significantly augmented, but did not approach entirely the magnitude observed in endemic controls. In onchocerciasis patients with concurrent mansonelliasis, cellular unresponsiveness to OvAg persisted, even when mf of O. volvulus were eliminated permanently by repeated ivermectin therapy. Cells from mf-positive onchocerciasis patients produced significantly less interferon-gamma (IFN-gamma) (P < 0.01) and interleukin-5 (IL-5) (P < 0.05) in response to OvAg than those taken from endemic controls or post-patent individuals in whom IFN-gamma and IL-5 production was similarly high. In contrast, both OvAg-driven as well as spontaneous IL-10 secretion was higher in mf-positive patients than in endemic controls or post-patent cases. In all individuals examined, serological recognition of OvAg by immunoglobulins was dominated by IgG4; in mf-positive patients OvAg of 205,000-12,000 molecular weight (MW) were strongly bound. In post-patent individuals, and similarly in endemic controls. OvAg recognition by IgG4 varied from intense (with numerous antigens being recognized) to weak or absent antigen binding. Significantly elevated OvAg-specific IgG isotypes were measured in mf-positive onchocerciasis patients in comparison with endemic controls or post-patent individuals (with the exception of IgG3). IgG1, IgG2 and IgE were higher, but IgG4 was lower in endemic controls compared with post-patent onchocerciasis patients. The ratios of IgG4/IgG1 differed (P < 0.001) between endemic controls and mf-positive or post-patent onchocerciasis patients, with IgG4/IgG1 ratios of R < 3.0 being characteristic for endemic controls and post-patent O. volvulus infection. In conclusion, this cross-sectional immunoepidemiological investigation showed that distinct states of O. volvulus infection correlate with a particular cellular and humoral immune response. The mf-free condition appeared to be associated with a vigorous parasite-specific cellular reactivity and a particular cytokine production profile, while concurrent M. perstans infection depressed OvAg-specific cellular responsiveness. Antibody responses, in all likelihood, reflected the intensity and state of infection, and not the degree of acquired immunity protective against parasite aggregation.

Adolescent↗
PubMed1997

Analysis of multiple Plasmodium falciparum infections in Tanzanian children during the phase III trial of the malaria vaccine SPf66.

In the first phase III efficacy trial of the malaria vaccine SPf66 in Africa, MOIs in SPf66- and placebo-vaccinated children were analyzed by polymerase chain reaction-restriction fragment length polymorphism of the Plasmodium falciparum merozoite surface antigen 2 (MSA2). MOIs were significantly reduced in asymptomatic vaccine recipients compared with those in asymptomatic placebo recipients; however, no differences were observed among symptomatic children in the vaccine and control groups. These results show that immunization with SPf66 modulates the course of naturally occurring infections, as reflected by reduced MOIs. In placebo recipients, however, there was a significant negative correlation between numbers of infecting genotypes, as identified by MSA2, and morbidity. Asymptomatic placebo recipients had an average of 5 concurrent infections, whereas children with clinical cases had an average of 3.4 infections. These data provide further evidence that premunition from concurrent infections is important in immunity against clinical malaria. No such effect of multiple infections was found in the vaccinated group.

Animals↗
PubMed1997

Actinomyces europaeus sp. nov., isolated from human clinical specimens.

Ten strains of a hitherto undescribed catalase-negative, facultatively anaerobic, coryneform bacterium were isolated or collected by workers at three European clinical bacteriology laboratories or reference centers. These strains were isolated from humans, and most came from abscess material. Biochemical and chemotaxonomic characterization revealed that the strains belonged to the genus Actinomyces. The phenotypic features of the 10 strains were incompatible with the descriptions of the previously established Actinomyces species. A comparative 16S rRNA gene sequence analysis demonstrated that the previously undescribed strains constitute a new line in the genus Actinomyces. The name Actinomyces europaeus sp. nov. is proposed for these clinical isolates. The type strain is CCUG 32789A.

Actinomyces↗
PubMed1997

Phenotypic and phylogenetic characterization of some Eubacterium-like isolates containing a novel type B wall murein from human feces: description of Holdemania filiformis gen. nov., sp. nov.

A group of Eubacterium-like strains (designated group S14), isolated from the feces of healthy people, was characterized by biochemical tests, fatty acid analysis, cell wall murein analysis, and 16S rDNA analysis. Our results indicate that group S14 is phylogenetically a member of the Clostridium subphylum of the gram-positive bacteria. Despite a phenotypic resemblance to the genus Eubacterium, group S14 was shown to be phylogenetically distantly related to the type species of the genus, Eubacterium limosum. Group S14 showed a specific phylogenetic association with Erysipelothrix rhusiopathiae. Group S14 resembled Erysipelothrix in possessing the uncommon type B cell wall murein. Structural analyses, however, revealed the presence of a previously unknown B1 delta (L-Ala)-D-Glu-Gly-L-Lys murein type. Based on a 16S rRNA sequence divergence of greater than 10% with E. rhusiopathiae and the presence of a unique murein type, a new genus, Holdemania, is proposed for group S14, with one species, Holdemania filiformis. Type strain of H. filiformis is ATCC 51649.

Cell Wall↗
PubMed1997

MRP 8/14 as marker for Plasmodium falciparum-induced malaria episodes in individuals in a holoendemic area.

Presence of Plasmodium falciparum parasites in the peripheral blood of patients in a holoendemic area does not necessarily show that their illness is due to malaria. The aim of the present project was therefore to look for biological markers related to symptomatology or clinical events during a malaria episode. We focused our work on a complex of heterodimeric calcium-binding proteins secreted by stimulated neutrophils and monocytes, named MIF or myeloid-related proteins (MRP 8/14). In a longitudinal study including 51 adults from Ifakara, Tanzania (84.7% prevalence for P. falciparum in adults during the study), the level of MRP 8/14 in the serum was significantly related to the parasite load (Spearman correlation coefficient, 0.52; P < 0.0001). In the serum from children up to 6 years admitted at a health post the MRP 8/14 levels were closely related to parasitemia but also to fever episodes (Spearman correlation coefficients, 0.96 and 0.736; P < 0.0001 and P < 0.001, respectively). Although not specific to malaria, the measurement of MRP 8/14 could be an additional tool in assessing malaria-related morbidity.

Adolescent↗
PubMed1997

Simple differential detection of Entamoeba histolytica and Entamoeba dispar in fresh stool specimens by sodium acetate-acetic acid-formalin concentration and PCR.

Amoebiasis is caused by two distinct species, a pathogenic form (Entamoeba histolytica) and a nonpathogenic form (Entamoeba dispar), which are morphologically identical. Although the distinction between these two species is of great clinical importance, the methods developed for this purpose either are very time-consuming or involve laborious procedures for isolation of the DNA. We report here a simple PCR method starting with fresh stool specimen that allows for the sensitive and reliable distinction between E. histolytica and E. dispar. After initial concentration by the sodium acetate-acetic acid-formalin (SAF) method and digestion with proteinase K, a 0.88-kb sequence of the multicopy 16S rRNA gene served as a target for PCR amplification. The method starting with unpreserved specimens proved to be very sensitive and was not influenced by the quick exposure to SAF fixative during the initial concentration step. However, storage in SAF fixative prior to testing resulted in a decreased sensitivity within 2 days. The detection limit of the method was as low as one copy of the 16S rRNA gene. No cross-reactivity was observed with other common intestinal protozoa. Mixed infections involving both E. histolytica and E. dispar could easily be detected at a ratio of 1:10,000 by agarose gel electrophoresis or a DNA hybridization immunoassay.

Acetic Acid↗
PubMed1997

Determination of total homocysteine in human plasma by isocratic high-performance liquid chromatography.

A simple, sensitive and precise isocratic HPLC method for the determination of total homocysteine in human plasma is described. The thiol compounds were liberated from plasma proteins by reduction with tri-n-butylphosphine and derivatized with a thiol-specific fluorogenic marker, 7-fluoro-benzo-2-oxa-1,3-diazole-4-sulphonate. The derivatives were separated isocratically within 7 min by reversed-phase HPLC using a Superspher 100 RP-18 column as stationary phase. By using this approach more than 200 samples a day can be assayed for total homocysteine. The method was linear up to 100 mumol/l and proved to be sensitive with a detection limit of 0.1 mumol/l and the lowest limit of reliable quantification of 0.5 mumol/l for homocysteine in buffer. Intra- and inter-assay coefficients of variation were both < 4% at a concentration of 10 mumol/l homocysteine. Similar results were obtained for homocysteine concentrations between 0.5 and 100 mumol/l. The analytical recovery for these concentrations ranged from 94.9 to 117.0%. As compared to other protocols published so far, this modified method is less complicated but equally sensitive and reproducible and allows a rapid determination of total homocysteine and cysteine in human plasma under routine conditions.

Chromatography, High Pressure Liquid↗
PubMed1997

The usefulness of three biallelic restriction fragment length polymorphisms versus a polymorphic dinucleotide tandem repeat polymorphism at the low-density-lipoprotein receptor gene locus for diagnosis of familial hypercholesterolemia.

Indirect molecular diagnosis of familial hypercholesterolemia is possible based on genetic linkage analysis of DNA polymorphisms at the low-density-lipoprotein receptor gene locus in family studies. The use of biallelic restriction fragment length polymorphisms, however, is restricted by their low degree of heterogeneity, and therefore several of these markers have to be combined. To overcome these restrictions we examined the value and applicability of an (AT)n tandem repeat polymorphism at the 3' untranslated region of the gene, alone and in combination with three biallelic restriction fragment length polymorphisms in 35 independent healthy subjects and in familial hypercholesterolemia families with 23 parents and 52 children. For each family one of the parents had the clinical diagnosis of familial hypercholesterolemia. The probands were genotyped using the TaqI, HincII and NcoI restriction fragment length polymorphism and the (AT)n tandem repeat polymorphism of the gene. The heterozygosity index (0.60) and the polymorphism information content (PIC value) (0.53) of the ATn repeat polymorphism were higher compared to each single biallelic restriction fragment length polymorphism (heterozygosity index 0.26-0.54; PIC value 0.24-0.36). The combined PIC value of all three biallelic restriction fragment length polymorphisms (0.79) was comparable to the combination of the HincII and the ATn polymorphism (0.74). Using these two markers, a definitive molecular diagnosis could be made in 36 children from 15 parents compared to just 12 parents and their children using the three biallelic restriction fragment length polymorphisms. We conclude that the ATn tandem repeat polymorphisms is useful for indirect molecular diagnosis of familial hypercholesterolemia in affected families.

Chromosome Mapping↗
PubMed1996

The chsA gene, encoding a class-I chitin synthase from Ampelomyces quisqualis.

Degenerate oligodeoxyribonucleotide primers, designed on the basis of conserved regions of the chitin synthase gene family, were used to amplify a fragment of the Ampelomyces quisqualis (Aq) chsA gene. Subsequently, the PCR product was used as a probe in order to identify and isolate genomic clones harboring the entire chsA gene. Aq chsA is 2786-nt long, has one intron and encodes a 910-amino-acid polypeptide belonging to the class-I chitin synthases. Low-stringency Southern hybridizations to Aq genomic DNA provided evidence for the presence of additional DNA fragments resembling chsA in the fungal genome, suggesting the presence of a multigene family of chitin synthases in Aq.

Amino Acid Sequence↗