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Biomedical subjects

A Widmer

Publications and source records attributed to A Widmer.

At least 37 records · Page 2Linked to original sources
PubMed1999

Nosocomial infections in Swiss university hospitals: a multi-centre survey and review of the published experience. Swiss-Noso Network.

A one-week period-prevalence survey, aimed at assessing the scale of nosocomial infections, was conducted in May 1996 in medical, surgical, and intensive care wards of 4 Swiss university hospitals. Standard definitions by the Centres for Disease Control and Prevention were used except that asymptomatic bacteriuria was not classified as a nosocomial infection. A total of 176 nosocomial infections were found among 156 of the 1349 surveyed patients (prevalence 11.6%; interhospital range 9.8-13.5%). Surgical site infections were most prevalent (30% of all nosocomial infections), followed by urinary tract (22%), lower respiratory tract (15%), and bloodstream infections (13%). The most frequently isolated microorganisms were Enterobacteriaceae (n = 44; 28%), S. aureus (n = 20; 13%), Pseudomonas spp (n = 17; 11%), and Candida spp (n = 16; 10%). One third of all episodes of nosocomial infections were not microbiologically documented. The overall prevalence of nosocomial infections in surgical patients (n = 562) was 16.2% compared to 8.6% for non-surgical patients (prevalence ratio, 1.9; 95% confidence interval [CI95], 1.4-2.5). In one centre, the in-hospital mortality of patients with nosocomial infections was 9.2% (10/109) compared to 3.9% (25/637) for patients without nosocomial infections (odds ratio, 2.47; CI95, 1.15-5.31). Infection rates were similar to those reported by two Swiss pilot studies from the early 1980s. This study offers a reliable measure of the prevalence of nosocomial infections in selected wards at 4 Swiss university hospitals and confirms the importance of nosocomial infections as a heavy burden on health services at the end of this century.

Blood-Borne Pathogens↗
PubMed1999

Floral mimicry: a fascinating yet poorly understood phenomenon.

Flowers of different species that resemble each other are not necessarily mimics. For mimicry to be occurring, the similarity must be adaptive. Unfortunately, no case of floral mimicry has ever been fully verified and it is important that we move beyond these perceived similarities to testing whether they are truly adaptive. Here we explain the differences between Batesian and Müllerian floral mimicry, illustrate what should be done to test mimicry hypotheses, and discuss how interspecific pollen transfer influences the evolution of mimicry.

Journal Article↗
PubMed1999

Use of organic solvents and small molecules for locating binding sites on proteins in solutions.

Application of a modified ePHOGSY and other NMR experiments to an H2O-DMSO solution of the protein FKBP12 identified the presence of one molecule of DMSO bound in the substrate binding site. It occupies the same spatial region occupied by the pipecolidine moiety of the immunosuppressive drugs FK506 and Rapamycin complexed to the protein. The binding constant K(D) for ths DMSO molecule was only 275 mM. A substructure search of small molecules similar to DMSO resulted in the identification of molecules with improved binding affinity. This work represents a clear example of the powerful interplay of molecular modelling and NMR.

Binding Sites↗
PubMed1999

The population genetic structure of a large temperate pollinator species, Bombus pascuorum (Scopoli) (Hymenoptera: Apidae)

The genetic population structure of the bumble bee Bombus pascuorum was studied using six microsatellite loci and a partial sequence of the mitochondrial gene cytochrome b. Eighteen populations from central and northern Europe were included in the analysis. Observed levels of genetic variability and heterozygosity were high. Estimates of population differentiation based on F- and phi-statistics revealed significant genetic differentiation among B. pascuorum populations and suggest that two partially isolated gene pools, separated by the Alps, do exist. The distribution of mtDNA haplo-types supports this view and presents direct evidence for gene flow across the Alps. Estimates of the number of migrants exchanged among populations north of the Alps suggest that historical events may have left a strong imprint on population structure.

Journal Article↗
PubMed1999

Extensive intraspecific chloroplast DNA (cpDNA) variation in the alpine Draba aizoides L. (Brassicaceae): haplotype relationships and population structure.

Chloroplast DNA (cpDNA) sequence variation is currently the most widely used tool for the inference of phylogenetic relationships among plants at all taxonomic levels. Generally, noncoding regions tend to evolve faster than coding sequences and have recently been applied to the study of phylogenetic relationships among closely related taxa. An implicit assumption of many of these studies is that intraspecific cpDNA variation is either absent or low and therefore will not interfere with the reconstruction of interspecific relationships. A survey of cpDNA sequence variation in the common alpine plant species Draba aizoides L. was undertaken to assess levels of intraspecific cpDNA sequence variation. These levels were compared to levels of interspecific sequence divergence between D. aizoides and related alpine Draba species. Intraspecific cpDNA sequence divergence was extensive in D. aizoides, and intraspecific differences were often larger than interspecific differences. cpDNA haplotype relationships were explored using a maximum parsimony approach and minimum-spanning networks. Results from both methods were largely congruent but comparisons provided interesting insights into the presumed evolutionary history of cpDNA haplotypes. A combined effect of cpDNA introgression and complex lineage sorting was inferred to explain the pattern of cpDNA variation found in D. aizoides. Our results suggest that intraspecific cpDNA variation can be extensive and that intraspecific variation needs to be taken into account when inferring phylogenetic relationships among closely related taxa.

Brassicaceae↗
PubMed1999

Genetic and Floral Divergence among Sympatric Populations of Gymnadenia conopsea s.l. (Orchideaceae) with Different Flowering Phenology.

Gymnadenia conopsea s.l. is a common orchid in central Europe, where early- and late-flowering populations can be distinguished. The early-flowering form is recognized as subspecies conopsea and the late-flowering form as subspecies densiflora. The two subspecies can occur in sympatry, but their flowering periods are separated. We investigated whether early- and late-flowering subspecies are genetically differentiated, whether they diverged once or repeatedly, and we tried to identify potential evolutionary forces involved in the divergence of the two subspecies. We used genetic markers to estimate genetic divergence within and among populations of early- and late-flowering G. conopsea, and to reconstruct their evolutionary history. In addition, we assessed morphological variation between subspecies. Allozyme variation indicated that subspecies conopsea was significantly more variable than ssp. densiflora and that gene flow among populations of ssp. conopsea was higher than among populations of ssp. densiflora. Gene flow between subspecies was low, indicating that the difference in flowering phenology represented an effective barrier to gene flow. A neighbor-joining tree based on allozyme frequencies indicated that early- and late- flowering populations did not diverge repeatedly in sympatry. Levels of cpDNA variation were generally low, even between G. conopsea s.l. and Gymnadenia odoratissima, chosen as an outgroup. Four cpDNA haplotypes were found, which differed only in the number of microsatellite repeats. Their distribution among subspecies of G. conopsea s.l. and G. odoratissima indicates that microsatellite haplotypes have evolved repeatedly, and their occurrence in different taxa thus represents a homoplasy. Floral characters were variable within and among populations and subspecies but did not consistently separate early- from late-flowering populations. A weak separation between subspecies was found in vegetative characters that presumably reflected habitat and competitive differences experienced by early- and late-flowering populations.

Journal Article↗
PubMed1999

Prevalence and risk factors for nosocomial infections in four university hospitals in Switzerland.

OBJECTIVE: To determine the prevalence and risk factors for nosocomial infections (NIs) in four Swiss university hospitals. DESIGN AND SETTING: A 1-week period-prevalence survey conducted in May 1996 in medical, surgical, and intensive-care wards of four Swiss university hospitals (900-1,500 beds). Centers for Disease Control and Prevention definitions were used, except that asymptomatic bacteriuria was not categorized as NI. Study variables included patient demographics, primary diagnosis, comorbidities, exposure to medical and surgical risk factors, and use of antimicrobials. Risk factors for NIs were determined using logistic regression with adjustment for length of hospital stay, study center, device use, and patients' comorbidities. RESULTS: 176 NI were recorded in 156 of 1,349 screened patients (11.6%; interhospital range, 9.8%-13.5%). The most frequent NI was surgical-site infection (53; 30%), followed by urinary tract infection (39; 22%), lower respiratory tract infection (27; 15%), and bloodstream infection (23; 13%). Prevalence of NI was higher in critical-care units (25%) than in medical (9%) and surgical wards (12%). Overall, 65% of NIs were culture-proven; the leading pathogens were Enterobacteriaceae (44; 28%), Staphylococcus aureus (20; 13%), Pseudomonas aeruginosa (17; 11%), and Candida species (16; 10%). Independent risk factors for NI were central venous catheter (CVC) use (odds ratio [OR], 3.35; 95% confidence interval [CI95], 2.91-3.80), admission to intensive care (OR, 1.75; CI95, 1.30-2.21), emergency admission (OR, 1.57; CI95, 1.15-2.00), impaired functional status (Karnofsky index 1-4: OR, 2.56; CI95, 1.953.17), and McCabe classification of ultimately fatal (OR, 2.50; CI95, 2.04-2.96) or rapidly fatal (OR, 2.25; CI95, 1.52-2.98) underlying condition. CONCLUSIONS: According to the results of this survey, NIs are frequent in Swiss university hospitals. This investigation confirms the importance of CVCs as a major risk factor for NI. Patient comorbidities must be taken into account to adjust for case mix in any study comparing interhospital or intrahospital infection rates.

Adolescent↗
PubMed1999

Human infection due to Ebola virus, subtype Côte d'Ivoire: clinical and biologic presentation.

In November 1994 after 15 years of epidemiologic silence, Ebola virus reemerged in Africa and, for the first time, in West Africa. In Côte d'Ivoire, a 34-year-old female ethologist was infected while conducting a necropsy on a wild chimpanzee. Eight days later, the patient developed a syndrome that did not respond to antimalarial drugs and was characterized by high fever, headache, chills, myalgia, and cough. The patient had abdominal pain, diarrhea, vomiting, and a macular rash, and was repatriated to Switzerland. The patient suffered from prostration and weight loss but recovered without sequelae. Laboratory findings included aspartate aminotransferase and alanine aminotransferase activity highly elevated, thrombocytopenia, lymphopenia, and, subsequently, neutrophilia. A new subtype of Ebola was isolated from the patient's blood on days 4 and 8. No serologic conversion was detected among contact persons in Côte d'Ivoire (n = 22) or Switzerland (n = 52), suggesting that infection-control precautions were satisfactory.

Adult↗
PubMed1999

Molecular evidence for allopolyploid speciation and a single origin of the narrow endemic Draba ladina (Brassicaceae).

Draba ladina (Brassicaceae) is a small alpine flower endemic to the Swiss Alps. It occurs exclusively at elevations between 2600 and 3000 m and is restricted to less than a dozen mountains in the Lower Engadin. Morphological characters and polyploidy suggest a hybrid origin. Potential diploid progenitor species are distributed widely and often occur sympatrically. To study the evolutionary history of D. ladina we assessed intra- and interspecific sequence variation at noncoding chloroplast DNA loci and nuclear rDNA ITS sequences in D. ladina and its presumed progenitor species D. aizoides, D. dubia, and D. tomentosa. A single ITS (Internal Transcribed Spacer) genotype was found in each of D. aizoides and D. dubia and two in D. tomentosa. Additivity of ITS sequences of D. aizoides and D. tomentosa was found in D. ladina, supporting the hypothesis of an allotetraploid origin. Intraspecific cpDNA variation was found in all diploid species, but not in D. ladina. The single chloroplast DNA haplotype found in the latter was closest to one cpDNA haplotype found in D. tomentosa, suggesting that D. tomentosa was the maternal parent. These results suggest that D. ladina is a relatively young, presumably postglacial, taxon with a single allopolyploid origin.

Journal Article↗
PubMed1996

Parasites and carotenoid-based signal intensity: how general should the relationship be?

Evidence that selection by parasites maintains heritable variation in sexually selected signals (Hamilton-Zuk model) has proved equivocal. Bright individuals do not always have fewer parasites in intraspecific comparisons. Because the lymphocyte-based defence system and the production of some colors used in sexual signaling require carotenoids, we consider a trade-off between defence against parasites and sexual signals. The nature and the sign of the covariance between defence and signal brightness can vary. Depending on carotenoid availability and allocation, and the type of sexual signal, various relationships between parasite load and signal intensity are expected.

Animals↗