Institute of Medical Microbiology and Hygiene

Freiburg, Germany

Institute of Medical Microbiology and Hygiene

Freiburg, Germany
Time filter
Source Type

Probst S.,Institute of Experimental and Clinical Pharmacology and Toxicology | Daza R.A.,Seattle Childrens Research InstituteSeattle 98101Washington | Bader N.,Institute of Experimental and Clinical Pharmacology and Toxicology | Hummel J.F.,Institute of Medical Microbiology and Hygiene | And 4 more authors.
Genesis | Year: 2017

The T-box transcription factor Eomes (also known as Tbr2) shows short-lived expression in various localized domains of the embryo, including epiblast cells during gastrulation and intermediate progenitor cells in the cerebral cortex. In these tissues Eomes fulfills crucial roles for lineage specification of progenitors. To directly observe Eomes-dependent cell lineages in the living embryo, we generated a novel dual-fluorescence reporter allele that expresses a membrane-bound tdTomato protein for investigation of cell morphology and a nuclear GFP for cell tracing. This allele recapitulates endogenous EOMES protein expression and is suitable for live imaging. We found that the allele can also be used as a short-to-medium-term lineage tracer, as GFP persists in cells longer than EOMES protein and marks Eomes-dependent lineages with a timeframe of days to weeks depending on the proliferation rate. In summary, we present a novel genetic tool for investigation of Eomes-dependent cell types by live imaging and lineage tracing. © 2017 Wiley Periodicals, Inc.

Grosz M.,University of Würzburg | Grosz M.,Institute for Hygiene and Medical Microbiology | Kolter J.,University of Würzburg | Paprotka K.,University of Würzburg | And 11 more authors.
Cellular Microbiology | Year: 2014

Staphylococcus aureus is a Gram-positive human pathogen that is readily internalized by professional phagocytes such as macrophages and neutrophils but also by non-professional phagocytes such as epithelial or endothelial cells. Intracellular bacteria have been proposed to play a role in evasion of the innate immune system and may also lead to dissemination within migrating phagocytes. Further, S.aureus efficiently lyses host cells with a battery of cytolytic toxins. Recently, phenol-soluble modulins (PSM) have been identified to comprise a genus-specific family of cytolytic peptides. Of these the PSMα peptides have been implicated in killing polymorphonuclear leucocytes after phagocytosis. We questioned if the peptides were active in destroying endosomal membranes to avoid lysosomal killing of the pathogen and monitored integrity of infected host cell endosomes by measuring the acidity of the intracellular bacterial microenvironment via flow cytometry and by a reporter recruitment technique. Isogenic mutants of the methicillin-resistant S.aureus (MRSA) strains USA300 LAC, USA400 MW2 as well as the strongly cytolytic methicillin-sensitive strain 6850 were compared with their respective wild type strains. In all three genetic backgrounds, PSMα mutants were unable to escape from phagosomes in non-professional (293, HeLa, EAhy.926) and professional phagocytes (THP-1), whereas mutants in PSMβ and δ-toxin as well as β-toxin, phosphatidyl inositol-dependent phospholipase C and Panton Valentine leucotoxin escaped with efficiencies of the parental strains. S.aureus replicated intracellularly only in presence of a functional PSMα operon thereby illustrating that bacteria grow in the host cell cytoplasm upon phagosomal escape. Staphylococcus aureus is efficiently taken up by mammalian cells but escapes the phagosome in an agr quorum sensing-controlled process. Clinical strains of S. aureus use PSMα, small amphiphilic peptides, to escape the phagosome and subsequently switch off quorum sensing-dependent transcription. S. aureus further replicates within the cytoplasm but not in the phagosome of its host cells. Phagosomal escape of S. aureus therefore marks a decisive phase in intracellular staphylococcal infections, which may constitute the basis for host cell death. © 2013 John Wiley & Sons Ltd.

Kleylein-Sohn J.,Novartis | Kleylein-Sohn J.,Friedrich Miescher Institute for Biomedical Research | Pollinger B.,Novartis | Ohmer M.,Novartis | And 5 more authors.
Journal of Cell Science | Year: 2012

Centrosomes represent the major microtubule organizing centers (MTOCs) of animal somatic cells and orchestrate bipolar spindle assembly during mitotic cell division. In meiotic cells, the kinesin HSET compensates for the lack of centrosomes by focusing acentrosomal MTOCs into two spindle poles. By clustering multiple centrosomes into two spindle poles, HSET also mediates bipolar mitosis in cancer cells with supernumerary centrosomes. However, although dispensable in non-transformed human cells, the role of HSET in cancer cells with two centrosomes has remained elusive. In this study, we demonstrate that HSET is required for proper spindle assembly, stable pole-focusing and survival of cancer cells irrespective of normal or supernumerary centrosome number. Strikingly, we detected pronounced acentrosomal MTOC structures in untreated mitotic cancer cells. While in most cancer cells these acentrosomal MTOCs were rapidly incorporated into the assembling bipolar spindle, some cells eventually established bipolar spindles with acentrosomal poles and free centrosomes. These observations demonstrate that acentrosomal MTOCs were functional and that both centrosomal and acentrosomal mechanisms were required for bipolar spindle organization. Our study shows that HSET is critical for clustering acentrosomal and centrosomal MTOCs during spindle formation in human cancer cells with two bona fide centrosomes. Furthermore, we show that in checkpoint-defective cancer cells, acentrosomal spindle formation and HSET-dependence are partially mediated by a constitutive activation of the DNA damage response. In summary, we propose that acentrosomal spindle assembly mechanisms are hyperactive in cancer cells and promote HSET, a key driver of acentrosomal spindle organization, as an attractive target for cancer therapy. © 2012. Published by The Company of Biologists Ltd.

Van Praet L.,Ghent University | Pircher H.,Institute of Medical Microbiology and Hygiene | Elewaut D.,Ghent University
Annals of the Rheumatic Diseases | Year: 2014

Objectives: Killer cell lectin-like receptor G1 (KLRG1) is an NK cell marker also expressed on T cells showing an immunosenescent phenotype. KLRG1 binding to its ligand E-cadherin inhibits functional responses. It was recently shown that soluble E-cadherin (sE-cadherin) also influences KLRG1 signalling, although its involvement in arthritis is unknown. Our goal was to evaluate the contribution of KLRG1+ T cells to synovitis. Methods: Paired peripheral blood (PB) and synovial fluid (SF) mononuclear cells from 21 patients with spondyloarthritis (SpA) or rheumatoid arthritis (RA), eight with crystal-induced arthritis and 10 controls were obtained. T cells were characterised for KLRG1 expression directly ex vivo, while TNF-α/IFN- γ production was assessed after polyclonal stimulation. Assays of chemotaxis response towards SF were conducted. Additionally, sE-cadherin levels in our paired samples were determined. Moreover, TNF-α/IFN-γ production by antigen-specific T cells was evaluated in the presence of sE-cadherin. Results: KLRG1+ T cells were enriched in SF as opposed to PB of SpA and RA patients, which contrasts with results obtained in crystal-induced arthritides. KLRG1+ T cells were more functionally active as opposed to KLRG1- T cells and migrated preferentially towards SpA and RA SF. sE-cadherin levels were higher in SF versus plasma. The presence of sE-cadherin enhanced the number of KLRG1+ CD4+ T cells able to produce TNF-α but not IFN-γ. Conclusions: sE-cadherin contributes to the local proinflammatory environment in the joint by favouring TNF-α production by KLRG1+ CD4+ T cells. This pathway seems to be operational in both SpA and RA, but not in crystal-induced arthritis.

PubMed | Institute of Medical Microbiology and Hygiene, University of Bonn, University of Vienna, Schulke & Mayr GmbH and 4 more.
Type: | Journal: GMS hygiene and infection control | Year: 2015

In developing hygiene strategies, in recent years, the major focus has been on the hands as the key route of infection transmission. However, there is a multitude of lesser-known and underestimated reservoirs for microorganisms which are the triggering sources and vehicles for outbreaks or sporadic cases of infection. Among those are water reservoirs such as sink drains, fixtures, decorative water fountains and waste-water treatment plants, frequently touched textile surfaces such as private curtains in hospitals and laundry, but also transvaginal ultrasound probes, parenteral drug products, and disinfectant wipe dispensers. The review of outbreak reports also reveals Gram-negative and multiple-drug resistant microorganisms to have become an increasingly frequent and severe threat in medical settings. In some instances, the causative organisms are particularly difficult to identify because they are concealed in biofilms or in a state referred to as viable but nonculturable, which eludes conventional culture media-based detection methods. There is an enormous preventative potential in these insights, which has not been fully tapped. New and emerging pathogens, novel pathogen detection methods, and hidden reservoirs of infection should hence be given special consideration when designing the layout of buildings and medical devices, but also when defining the core competencies for medical staff, establishing programmes for patient empowerment and education of the general public, and when implementing protocols for the prevention and control of infections in medical, community and domestic settings.

Wagar L.E.,University of Toronto | Gentleman B.,University of British Columbia | Pircher H.,Institute of Medical Microbiology and Hygiene | McElhaney J.E.,University of British Columbia | And 2 more authors.
PLoS ONE | Year: 2011

T cells specific for persistent pathogens accumulate with age and express markers of immune senescence. In contrast, much less is known about the state of T cell memory for acutely infecting pathogens. Here we examined T cell responses to influenza in human peripheral blood mononuclear cells from older (>64) and younger (<40) donors using whole virus restimulation with influenza A (A/PR8/34) ex vivo. Although most donors had pre-existing influenza reactive T cells as measured by IFNγ production, older donors had smaller populations of influenza-responsive T cells than young controls and had lost a significant proportion of their CD45RA-negative functional memory population. Despite this apparent dysfunction in a proportion of the older T cells, both old and young donors' T cells from 2008 could respond to A/California/07/2009 ex vivo. For HLA-A2+ donors, MHC tetramer staining showed that a higher proportion of influenza-specific memory CD8 T cells from the 65+ group co-express the markers killer cell lectin-like receptor G1 (KLRG1) and CD57 compared to their younger counterparts. These markers have previously been associated with a late differentiation state or immune senescence. Thus, memory CD8 T cells to an acutely infecting pathogen show signs of advanced differentiation and functional deterioration with age. There was a significant negative correlation between the frequency of KLRG1 +CD57 + influenza M1-specific CD8 T cells pre-vaccination and the ability to make antibodies in response to vaccination with seasonal trivalent inactivated vaccine, whereas no such trend was observed when the total CD8 +KLRG1 +CD57 + population was analyzed. These results suggest that the state of the influenza-specific memory CD8 T cells may be a predictive indicator of a vaccine responsive healthy immune system in old age. © 2011 Wagar et al.

Grundemann C.,Institute of Medical Microbiology and Hygiene | Schwartzkopff S.,Institute of Medical Microbiology and Hygiene | Koschella M.,Institute of Medical Microbiology and Hygiene | Schweier O.,Institute of Medical Microbiology and Hygiene | And 3 more authors.
European Journal of Immunology | Year: 2010

The killer cell lectin-like receptor G1 (KLRG1) is expressed by NK and T-cell subsets and recognizes members of the classical cadherin family. KLRG1 is widely used as a lymphocyte differentiation marker in both humans andmice but the physiological role of KLRG1 in vivo is still unclear. Here, we generated KLRG1-deficient mice by homologous recombination and used several infection models for their characterization. The results revealed that KLRG1 deficiency did not affect development and function of NK cells examined under various conditions. KLRG1 was also dispensable for normal CD8+ T-cell differentiation and function after viral infections. Thus, KLRG1 is a marker for distinct NK and T-cell differentiation stages but it does not play a deterministic role in the generation and functional characteristics of these lymphocyte subsets. In addition, we demonstrate that E-cadherin expressed by K562 target cells inhibited NK-cell reactivity in transgenic mice over-expressing KLRG1 but not in KLRG1-deficient or WT mice. Hence, the inhibitory potential of KLRG1 in mice is rather weak and strong activation signals during viral infectionsmay override the inhibitory signal in vivo. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

PubMed | Institute of Medical Microbiology and Hygiene, 2. Chirurgische Abteilung and 4. Medizinische Abteilung mit Infektiologie und Tropenmedizin
Type: Journal Article | Journal: Wiener klinische Wochenschrift | Year: 2016

We report on two cases of necrotizing fasciitis of the lower leg due to nontoxigenic Vibrio cholerae (V. cholerae). A 73-year-old woman (case 1) and an 80-year-old man (case 2) were hospitalized with symptoms of necrotizing fasciitis on July 18 and August 15, 2015, respectively. In both cases, symptoms started the day after swimming in local ponds. Swabs gained intraoperatively and a blood culture from the male patient, yielded V. cholerae non-O1/non-O139, negative for cholera toxin gene ctx and positive for hemolysin genes hlyA and hlyB. Water samples taken from pond A on August 17, 2015 (32 days after exposure of case 1) and from pond B on August 20, 2015 (7 days after exposure of case 2) yielded non-O1/non-O139 V. cholerae in most-probable numbers of >11,000 per 100 ml each. The occurrence of two cases of necrotizing fasciitis within a 1 month period related to two Austrian non-saline bathing waters, previously not known to harbor V. cholerae, is probably linked to the prevailing extreme weather conditions (heat wave, drought) this summer in Austria. While case 1 was discharged in good clinical condition after 73 days, case 2 died after four months of hospitalization. Public health authorities are challenged to assess the effects of long-term climate change on pathogen growth and survival in continental bodies of fresh water.

Wewalka G.,Institute for Medical Microbiology and Hygiene | Schmid D.,Institute for Medical Microbiology and Hygiene | Harrison T.G.,Microbiology Service Division | Uldum S.A.,Statens Serum Institute | Luck C.,Institute of Medical Microbiology and Hygiene
Clinical Microbiology and Infection | Year: 2014

In 2010 a case of a dual infection with Legionella pneumophila serogroup (sg) 1 and sg 3 was identified by culture of a blood sample collected from a female Austrian patient with septic pneumonia. Subsequently all 35 European National Legionella Reference Laboratories were interviewed regarding the frequency of dual infections in legionellosis. The Reference Laboratories in Denmark, the UK and Germany reported the detection of another 14 cases of dual infections with different Legionella strains between 2002 and 2012. Among the 15 cases, there were four cases with different Legionella species, six cases with different L. pneumophila serogroups, and five cases of dual infections with L. pneumophila sg 1 with different MAb-types. The median age of the 15 cases was 56 years and the male to female ratio 1:1.14. Six of the 15 patients were receiving immunosuppressive treatment following organ transplantation (n = 3) or for underlying haematological and solid malignancies (n = 3). Five of the 15 cases died within 30 days following diagnosis. Efforts to detect dual infections with different Legionella strains will improve our ability to correctly elucidate the causative sources of infection and enhance our understanding of the epidemiology of Legionella infections. © 2013 European Society of Clinical Microbiology and Infectious Diseases.

Nagaraj V.A.,Indian Institute of Science | Nagaraj V.A.,Nanyang Technological University | Arumugam R.,Indian Institute of Science | Arumugam R.,Jacobs University Bremen | And 4 more authors.
Molecular and Biochemical Parasitology | Year: 2010

Earlier studies in this laboratory had shown that the malarial parasite can synthesize heme de novo and inhibition of the pathway leads to death of the parasite. It has been proposed that the pathway for the biosynthesis of heme in Plasmodium falciparum is unique involving three different cellular compartments, namely mitochondrion, apicoplast and cytosol. Experimental evidences are now available for the functionality and localization of all the enzymes of this pathway, except protoporphyrinogen IX oxidase (PfPPO), the penultimate enzyme. In the present study, PfPPO has been cloned, expressed and shown to be localized to the mitochondrion by immunofluorescence microscopy. Interestingly, the enzyme has been found to be active only under anaerobic conditions and is dependent on electron transport chain (ETC) acceptors for its activity. The native enzyme present in the parasite is inhibited by the ETC inhibitors, atovaquone and antimycin. Atovaquone, a well known inhibitor of parasite dihydroorotate dehydrogenase, dependent on the ETC, inhibits synthesis of heme as well in P. falciparum culture. A model is proposed to explain the ETC dependence of both the pyrimidine and heme-biosynthetic pathways in P. falciparum. © 2010 Elsevier B.V.

Loading Institute of Medical Microbiology and Hygiene collaborators
Loading Institute of Medical Microbiology and Hygiene collaborators