TY - JOUR A1 - Lehnert, Teresa A1 - Prauße, Maria T. E. A1 - Hünniger, Kerstin A1 - Praetorius, Jan-Philipp A1 - Kurzai, Oliver A1 - Figge, Marc Thilo T1 - Comparative assessment of immune evasion mechanisms in human whole-blood infection assays by a systems biology approach JF - PLOS ONE N2 - Computer simulations of mathematical models open up the possibility of assessing hypotheses generated by experiments on pathogen immune evasion in human whole-blood infection assays. We apply an interdisciplinary systems biology approach in which virtual infection models implemented for the dissection of specific immune mechanisms are combined with experimental studies to validate or falsify the respective hypotheses. Focusing on the assessment of mechanisms that enable pathogens to evade the immune response in the early time course of a whole-blood infection, the least-square error (LSE) as a measure for the quantitative agreement between the theoretical and experimental kinetics is combined with the Akaike information criterion (AIC) as a measure for the model quality depending on its complexity. In particular, we compare mathematical models with three different types of pathogen immune evasion as well as all their combinations: (i) spontaneous immune evasion, (ii) evasion mediated by immune cells, and (iii) pre-existence of an immune-evasive pathogen subpopulation. For example, by testing theoretical predictions in subsequent imaging experiments, we demonstrate that the simple hypothesis of having a subpopulation of pre-existing immune-evasive pathogens can be ruled out. Furthermore, in this study we extend our previous whole-blood infection assays for the two fungal pathogens Candida albicans and C. glabrata by the bacterial pathogen Staphylococcus aureus and calibrated the model predictions to the time-resolved experimental data for each pathogen. Our quantitative assessment generally reveals that models with a lower number of parameters are not only scored with better AIC values, but also exhibit lower values for the LSE. Furthermore, we describe in detail model-specific and pathogen-specific patterns in the kinetics of cell populations that may be measured in future experiments to distinguish and pinpoint the underlying immune mechanisms. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-363343 VL - 16 ER - TY - JOUR A1 - Lehnert, Teresa A1 - Leonhardt, Ines A1 - Timme, Sandra A1 - Thomas-Rüddel, Daniel A1 - Bloos, Frank A1 - Sponholz, Christoph A1 - Kurzai, Oliver A1 - Figge, Marc Thilo A1 - Hünniger, Kerstin T1 - Ex vivo immune profiling in patient blood enables quantification of innate immune effector functions JF - Scientific Reports N2 - The assessment of a patient’s immune function is critical in many clinical situations. In complex clinical immune dysfunction like sepsis, which results from a loss of immune homeostasis due to microbial infection, a plethora of pro- and anti-inflammatory stimuli may occur consecutively or simultaneously. Thus, any immunomodulatory therapy would require in-depth knowledge of an individual patient’s immune status at a given time. Whereas lab-based immune profiling often relies solely on quantification of cell numbers, we used an ex vivo whole-blood infection model in combination with biomathematical modeling to quantify functional parameters of innate immune cells in blood from patients undergoing cardiac surgery. These patients experience a well-characterized inflammatory insult, which results in mitigation of the pathogen-specific response patterns towards Staphylococcus aureus and Candida albicans that are characteristic of healthy people and our patients at baseline. This not only interferes with the elimination of these pathogens from blood, but also selectively augments the escape of C. albicans from phagocytosis. In summary, our model could serve as a valuable functional immune assay for recording and evaluating innate responses to infection. KW - computational biology and bioinformatics KW - computational models KW - immunology KW - infection KW - inflammation KW - innate immunity Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-363337 VL - 11 ER - TY - JOUR A1 - Apsemidou, Athanasia A1 - Füller, Miriam Antonie A1 - Idelevich, Evgeny A. A1 - Kurzai, Oliver A1 - Tragiannidis, Athanasios A1 - Groll, Andreas H. T1 - Candida lusitaniae breakthrough fungemia in an immuno-compromised adolescent: case report and review of the literature JF - Journal of Fungi N2 - Candida lusitaniae is a rare cause of candidemia that is known for its unique capability to rapidly acquire resistance to amphotericin B. We report the case of an adolescent with grade IV graft-vs.-host disease after hematopoietic cell transplantation who developed catheter-associated C. lusitaniae candidemia while on therapeutic doses of liposomal amphotericin B. We review the epidemiology of C. lusitaniae bloodstream infections in adult and pediatric patients, the development of resistance, and its role in breakthrough candidemia. Appropriate species identification, in vitro susceptibility testing, and source control are pivotal to optimal management of C. lusitaniae candidemia. Initial antifungal therapy may consist of an echinocandin and be guided by in vitro susceptibility and clinical response. KW - Candida lusitaniae KW - candidemia KW - resistance KW - breakthrough KW - infection KW - transplantation Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-220125 SN - 2309-608X VL - 6 IS - 4 ER - TY - JOUR A1 - Weiss, Esther A1 - Schlegel, Jan A1 - Terpitz, Ulrich A1 - Weber, Michael A1 - Linde, Jörg A1 - Schmitt, Anna-Lena A1 - Hünniger, Kerstin A1 - Marischen, Lothar A1 - Gamon, Florian A1 - Bauer, Joachim A1 - Löffler, Claudia A1 - Kurzai, Oliver A1 - Morton, Charles Oliver A1 - Sauer, Markus A1 - Einsele, Hermann A1 - Loeffler, Juergen T1 - Reconstituting NK Cells After Allogeneic Stem Cell Transplantation Show Impaired Response to the Fungal Pathogen Aspergillus fumigatus JF - Frontiers in Immunology N2 - Delayed natural killer (NK) cell reconstitution after allogeneic stem cell transplantation (alloSCT) is associated with a higher risk of developing invasive aspergillosis. The interaction of NK cells with the human pathogen Aspergillus (A.) fumigatus is mediated by the fungal recognition receptor CD56, which is relocated to the fungal interface after contact. Blocking of CD56 signaling inhibits the fungal mediated chemokine secretion of MIP-1α, MIP-1β, and RANTES and reduces cell activation, indicating a functional role of CD56 in fungal recognition. We collected peripheral blood from recipients of an allograft at defined time points after alloSCT (day 60, 90, 120, 180). NK cells were isolated, directly challenged with live A. fumigatus germ tubes, and cell function was analyzed and compared to healthy age and gender-matched individuals. After alloSCT, NK cells displayed a higher percentage of CD56\(^{bright}\)CD16\(^{dim}\) cells throughout the time of blood collection. However, CD56 binding and relocalization to the fungal contact side were decreased. We were able to correlate this deficiency to the administration of corticosteroid therapy that further negatively influenced the secretion of MIP-1α, MIP-1β, and RANTES. As a consequence, the treatment of healthy NK cells ex vivo with corticosteroids abrogated chemokine secretion measured by multiplex immunoassay. Furthermore, we analyzed NK cells regarding their actin cytoskeleton by Structured Illumination Microscopy (SIM) and flow cytometry and demonstrate an actin dysfunction of NK cells shown by reduced F-actin content after fungal co-cultivation early after alloSCT. This dysfunction remains until 180 days post-alloSCT, concluding that further actin-dependent cellular processes may be negatively influenced after alloSCT. To investigate the molecular pathomechansism, we compared CD56 receptor mobility on the plasma membrane of healthy and alloSCT primary NK cells by single-molecule tracking. The results were very robust and reproducible between tested conditions which point to a different molecular mechanism and emphasize the importance of proper CD56 mobility. KW - natural killer cell KW - stem cell transplantation KW - corticosteroids KW - CCL3 KW - CCL4 KW - CCL5 Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-212581 SN - 1664-3224 VL - 11 ER - TY - JOUR A1 - Springer, Jan A1 - Walther, Grit A1 - Rickerts, Volker A1 - Hamprecht, Axel A1 - Willinger, Birgit A1 - Teschner, Daniel A1 - Einsele, Hermann A1 - Kurzai, Oliver A1 - Loeffler, Juergen T1 - Detection of Fusarium Species in Clinical Specimens by Probe-Based Real-Time PCR JF - Journal of Fungi N2 - The mold Fusarium is a ubiquitous fungus causing plant, animal and human infections. In humans, Fusarium spp. are the major cause of eye infections in patients wearing contact lenses or after local trauma. Systemic infections by Fusarium spp. mainly occur in immunosuppressed patients and can disseminate throughout the human body. Due to high levels of resistance to antifungals a fast identification of the causative agent is an urgent need. By using a probe-based real-time PCR assay specific for the genus Fusarium we analysed several different clinical specimens detecting Fusarium spp. commonly found in clinical samples in Germany. Also, a large collection of lung fluid samples of haematological patients was analysed (n = 243). In these, two samples (0.8%) were reproducibly positive, but only one could be confirmed by sequencing. For this case of probable invasive fungal disease (IFD) culture was positive for Fusarium species. Here we describe a rapid, probe-based real-time PCR assay to specifically detect DNA from a broad range of Fusarium species and its application to clinically relevant specimens. KW - probe-based real-time PCR KW - Fusarium KW - bronchoalveolar lavage fluid KW - fungal molecular diagnostics Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-193111 SN - 2309-608X VL - 5 IS - 4 ER - TY - JOUR A1 - Walther, Grit A1 - Wagner, Lysett A1 - Kurzai, Oliver T1 - Updates on the taxonomy of Mucorales with an emphasis on clinically important taxa JF - Journal of Fungi N2 - Fungi of the order Mucorales colonize all kinds of wet, organic materials and represent a permanent part of the human environment. They are economically important as fermenting agents of soybean products and producers of enzymes, but also as plant parasites and spoilage organisms. Several taxa cause life-threatening infections, predominantly in patients with impaired immunity. The order Mucorales has now been assigned to the phylum Mucoromycota and is comprised of 261 species in 55 genera. Of these accepted species, 38 have been reported to cause infections in humans, as a clinical entity known as mucormycosis. Due to molecular phylogenetic studies, the taxonomy of the order has changed widely during the last years. Characteristics such as homothallism, the shape of the suspensors, or the formation of sporangiola are shown to be not taxonomically relevant. Several genera including Absidia, Backusella, Circinella, Mucor, and Rhizomucor have been amended and their revisions are summarized in this review. Medically important species that have been affected by recent changes include Lichtheimia corymbifera, Mucor circinelloides, and Rhizopus microsporus. The species concept of Rhizopus arrhizus (syn. R. oryzae) is still a matter of debate. Currently, species identification of the Mucorales is best performed by sequencing of the internal transcribed spacer (ITS) region. Ecologically, the Mucorales represent a diverse group but for the majority of taxa, the ecological role and the geographic distribution remain unknown. Understanding the biology of these opportunistic fungal pathogens is a prerequisite for the prevention of infections, and, consequently, studies on the ecology of the Mucorales are urgently needed. KW - Mucorales KW - taxonomy KW - pathogens KW - identification KW - ecology KW - Circinella KW - Lichtheimia KW - Mucor KW - Rhizomucor KW - Rhizopus Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-193081 SN - 2309-608X VL - 5 IS - 4 ER - TY - JOUR A1 - Al-Zaben, Naim A1 - Medyukhina, Anna A1 - Dietrich, Stefanie A1 - Marolda, Alessandra A1 - Hünniger, Kerstin A1 - Kurzai, Oliver A1 - Figge, Marc Thilo T1 - Automated tracking of label-free cells with enhanced recognition of whole tracks JF - Scientific Reports N2 - Migration and interactions of immune cells are routinely studied by time-lapse microscopy of in vitro migration and confrontation assays. To objectively quantify the dynamic behavior of cells, software tools for automated cell tracking can be applied. However, many existing tracking algorithms recognize only rather short fragments of a whole cell track and rely on cell staining to enhance cell segmentation. While our previously developed segmentation approach enables tracking of label-free cells, it still suffers from frequently recognizing only short track fragments. In this study, we identify sources of track fragmentation and provide solutions to obtain longer cell tracks. This is achieved by improving the detection of low-contrast cells and by optimizing the value of the gap size parameter, which defines the number of missing cell positions between track fragments that is accepted for still connecting them into one track. We find that the enhanced track recognition increases the average length of cell tracks up to 2.2-fold. Recognizing cell tracks as a whole will enable studying and quantifying more complex patterns of cell behavior, e.g. switches in migration mode or dependence of the phagocytosis efficiency on the number and type of preceding interactions. Such quantitative analyses will improve our understanding of how immune cells interact and function in health and disease. KW - image processing KW - software Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-221093 VL - 9 ER - TY - JOUR A1 - Prauße, Maria T. E. A1 - Lehnert, Teresa A1 - Timme, Sandra A1 - Hünniger, Kerstin A1 - Leonhardt, Ines A1 - Kurzai, Oliver A1 - Figge, Marc Thilo T1 - Predictive Virtual Infection Modeling of Fungal Immune Evasion in Human Whole Blood JF - Frontiers in Immunology N2 - Bloodstream infections by the human-pathogenic fungi Candida albicans and Candida glabrata increasingly occur in hospitalized patients and are associated with high mortality rates. The early immune response against these fungi in human blood comprises a concerted action of humoral and cellular components of the innate immune system. Upon entering the blood, the majority of fungal cells will be eliminated by innate immune cells, i.e., neutrophils and monocytes. However, recent studies identified a population of fungal cells that can evade the immune response and thereby may disseminate and cause organ dissemination, which is frequently observed during candidemia. In this study, we investigate the so far unresolved mechanism of fungal immune evasion in human whole blood by testing hypotheses with the help of mathematical modeling. We use a previously established state-based virtual infection model for whole-blood infection with C. albicans to quantify the immune response and identified the fungal immune-evasion mechanism. While this process was assumed to be spontaneous in the previous model, we now hypothesize that the immune-evasion process is mediated by host factors and incorporate such a mechanism in the model. In particular, we propose, based on previous studies that the fungal immune-evasion mechanism could possibly arise through modification of the fungal surface by as of yet unknown proteins that are assumed to be secreted by activated neutrophils. To validate or reject any of the immune-evasion mechanisms, we compared the simulation of both immune-evasion models for different infection scenarios, i.e., infection of whole blood with either C. albicans or C. glabrata under non-neutropenic and neutropenic conditions. We found that under non-neutropenic conditions, both immune-evasion models fit the experimental data from whole-blood infection with C. albicans and C. glabrata. However, differences between the immune-evasion models could be observed for the infection outcome under neutropenic conditions with respect to the distribution of fungal cells across the immune cells. Based on these predictions, we suggested specific experimental studies that might allow for the validation or rejection of the proposed immune-evasion mechanism. KW - immune evasion KW - state-based model KW - innate immune response KW - polymorphonuclear neutrophils KW - whole-blood infection assay Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-197493 SN - 1664-3224 VL - 9 IS - 560 ER - TY - JOUR A1 - Weiss, Esther A1 - Ziegler, Sabrina A1 - Fliesser, Mirjam A1 - Schmitt, Anna-Lena A1 - Hünniger, Kerstin A1 - Kurzai, Oliver A1 - Morton, Charles-Oliver A1 - Einsele, Hermann A1 - Loeffler, Juergen T1 - First Insights in NK—DC Cross-Talk and the Importance of Soluble Factors During Infection With Aspergillus fumigatus JF - Frontiers in Cellular and Infection Microbiology N2 - Invasive aspergillosis (IA) is an infectious disease caused by the fungal pathogen Aspergillus fumigatus that mainly affects immunocompromised hosts. To investigate immune cell cross-talk during infection with A. fumigatus, we co-cultured natural killer (NK) cells and dendritic cells (DC) after stimulation with whole fungal structures, components of the fungal cell wall, fungal lysate or ligands for distinct fungal receptors. Both cell types showed activation after stimulation with fungal components and were able to transfer activation signals to the counterpart not stimulated cell type. Interestingly, DCs recognized a broader spectrum of fungal components and thereby initiated NK cell activation when those did not recognize fungal structures. These experiments highlighted the supportive function of DCs in NK cell activation. Furthermore, we focused on soluble DC mediated NK cell activation and showed that DCs stimulated with the TLR2/Dectin-1 ligand zymosan could maximally stimulate the expression of CD69 on NK cells. Thus, we investigated the influence of both receptors for zymosan, Dectin-1 and TLR2, which are highly expressed on DCs but show only minimal expression on NK cells. Specific focus was laid on the question whether Dectin-1 or TLR2 signaling in DCs is important for the secretion of soluble factors leading to NK cell activation. Our results show that Dectin-1 and TLR2 are negligible for NK cell activation. We conclude that besides Dectin-1 and TLR2 other receptors on DCs are able to compensate for the missing signal. KW - natural killer cells KW - dendritic cells KW - NK-DC cross-talk KW - Aspergillus fumigatus KW - soluble factors KW - innate immunity Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-233565 VL - 8 ER - TY - THES A1 - Kurzai, Oliver T1 - Molekulare Charakterisierung pH-regulierter Gene bei der humanpathogenen Hefespezies Candida dubliniensis und ihr Nutzen für die epidemiologische Diagnostik T1 - PH-regulated genes of the pathogenic yeast Candida dubliniensis and their impact in epidemiological diagnostics N2 - Candida dubliniensis ist eine 1995 erstmals beschriebene pathogene Hefespezies mit enger phylogenetischer Verwandtschaft zu Candida albicans. Sie wird mittels routinemäßig angewendeter Verfahren nicht von C. albicans unterschieden, weil sie als einzige Spezies im Genus Candida neben C. albicans Chlamydosporen ausbilden kann. C. dubliniensis ist bisher vor allem aus dem Oropharynx HIV-positiver Patienten isoliert worden. PHR1 und PHR2 sind funktionell homologe, pH-abhängig exprimierte Gene von C. albicans, deren Produkte essentiell für die Verknüpfung von b-1,3- und b-1,6-Glukan in der Zellwand sind. Die Deletion jedes dieser Gene führt zu einem pH-abhängigen Phänotyp mit aberranter Morphogenese in vitro und reduzierter Virulenz im Tiermodell. In dieser Arbeit werden PHR homologe Gene im Genom von C. dubliniensis charakterisiert. CdPHR1 weist eine Homologie von 90,5 Prozent zu PHR1 und CdPHR2 eine Homologie von 91,7 Prozent zu PHR2 auf. Wie PHR1 wird auch CdPHR1 nur unter neutralen und alkalischen Bedingungen exprimiert, während sich CdPHR2 Transkript, wie das von PHR2, nur unter sauren Bedingungen nachweisen lässt. Die funktionelle Homologie von CdPHR1 zu PHR1 wird durch Komplementation des Phänotyps einer C. albicans phr1 Mutante mit CdPHR1 gezeigt. Dabei erweist sich der native Promoter von CdPHR1 als funktional in C. albicans. Im Modellorganismus Saccharomyces cerevisiae wird CdPHR1 unter Kontrolle seines nativen Promotors dagegen pH-unabhängig exprimiert. Auch die zusätzliche Einführung eines mutierten, dominant aktiven Allels von RIM101, das in C. albicans für die pH-abhängige Genexpression verantwortlich ist, hat darauf keinen Einfluss. In C. glabrata und Aspergillus nidulans findet sich keine Expression von CdPHR1. Basierend auf Sequenzunterschieden zwischen PHR1 und CdPHR1 wird ein PCR-Schnelltest zur Speziesunterscheidung entwickelt. Dieser wird in einer epidemiologischen Studie mit 133 chlamydosporenpositiven klinischen Isolaten evaluiert. 21 oropharyngeale Isolate von 14 HIV-positiven Patienten können so retrospektiv als C. dubliniensis klassifiziert werden, dies entspricht einer Prävalenz von C. dubliniensis in diesem Kollektiv von 30 Prozent. Die Ergebnisse der PCR werden durch Sequenzierung ribosomaler Gene (V3, ITS1, ITS2) bestätigt. Parallel werden phänotypische Tests zur Identifizierung von C. dubliniensis auf ihre diagnostische Validität getestet. Während sich die Chlamydosporenmorphologie der Isolate und die Koloniefärbung auf dem Farbindikatormedium CHROMagar Candida als unzulänglich für die Unterscheidung erweisen und das für C. dubliniensis beschriebene Wachstumsdefizit bei 45°C zwar sensitiv, nicht aber spezifisch für die Identifizierung dieser Spezies ist, korreliert die Koloniemorphologie auf Staib-Agar zu 100 Prozent mit den molekularen Daten. Alle C. dubliniensis Isolate werden in einem biochemischen Assay (Micronaut RC) untersucht, dabei zeigt der Test auf b-Glukosidase Aktivität hohes diskriminatorisches Potenzial. In Resistenztestungen zeigen sich die C. dubliniensis Isolate sensibler als die oropharyngealen C. albicans Isolate gegen gebräuchliche Antimykotika. In dieser Studie kann gezeigt werden, dass C. dubliniensis und C. albicans auf teilweise austauschbare Mechanismen zur Reaktion auf Alterationen des pH-Milieus verfügen. Die pH-abhängige Regulation zellwandassoziierter Gene ist dabei eng mit morphogenetischen Prozessen verbunden. Trotz dieser Ähnlichkeit ist C. dubliniensis nicht nur weniger virulent als C. albicans, sondern zeigt auch ein unterschiedliches epidemiologisches Spektrum, das durch eine Spezialisierung auf oropharyngeale Kolonisation und Infektion bei HIV-positiven Patienten gekennzeichnet ist. Um die Gründe für diese Unterschiede aufzeigen zu können, ist eine verlässliche Identifizierung von C. dubliniensis notwendig. Dazu stellen die präsentierten Daten einerseits einen schnellen und verlässlichen PCR Test, andererseits eine sorgfältige Evaluierung derzeit gebräuchlicher phänotypischer Verfahren vor. Phänotypisch und genotypisch exzellent charakterisierte Isolate beider Spezies stehen für weitere Untersuchungen zur Verfügung. N2 - Candida dubliniensis is a recently described pathogenic yeast species that is phylogenetically closely related to Candida albicans. In routine clinical diagnostic procedures both species are not differentiated due to the unique ability of C. dubliniensis to form germ-tubes and chlamydospores as C. albicans. Most C. dubliniensis isolates have been recovered from the oropharynx of HIV-infected patients. PHR1 and PHR2 are functionally homologous genes of C. albicans responsible for crosslinking b-1,3- and b-1,6-glucans of the yeast cell wall. These genes are characterized by a unique pattern of pH-dependent transcription. Deletion of each of these genes results in a pH-dependent phenotype with aberrant in vitro morphogenesis and reduced virulence in an animal model. Here, PHR homologous genes of C. dubliniensis are characterized. CdPHR1 is 90.5 per cent homologous to PHR1, CdPHR2 is 91.7 per cent homologous to PHR2. Like PHR1, CdPHR1 is only expressed in neutral to alkaline conditions, whereas CdPHR2 transcript - as with PHR2 - can only be found in acidic conditions. Functional homology of CdPHR1 with PHR1 is shown by complementation of a phr1 phenotype in C. albicans with CdPHR1. The native promoter of CdPHR1 is thereby shown to be functional in C. albicans. In contrast CdPHR1 is expressed in a pH-independent manner in bakers yeast Saccharomyces cerevisiae. This constitutive expression is not altered by additional integration of a dominant active allele of RIM101, encoding the transcription factor, that ensures pH-dependent gene expression in C. albicans. CdPHR1 is not expressed in C. glabrata and Aspergillus nidulans. A rapid PCR-test for discrimination between C. albicans and C. dubliniensis is constructed based on sequence differences between PHR1 and CdPHR1. This test is evaluated in an epidemiological study with 133 chlamydospore-positive clinical yeast isolates. 21 oropharyngeal isolates are retrospectively identified as C. dubliniensis, resulting in a prevalence of 30 per cent in this patient collective. PCR-results are confirmed by sequencing rDNA (V3, ITS1, ITS2). Phenotypic tests for identification of C. dubliniensis are evaluated with respect to their diagnostic potential. Whereas chlamydospore-morphology and colony colour on Chromagar Candida are not suited for reliable discrimination, and the growth deficit of C. dubliniensis at 45°C is sensitive but not specific, colony morphology on Staib agar corresponds 100 per cent to the molecular biology data. All C. dubliniensis isolates are biochemically characterized using the Micronaut RC system. The test for b-glucosidase activity within this system shows a high discriminatory potential. Susceptibility testing reveals, that the C. dubliniensis isolates are more sensitive to antifungals than the C. albicans isolates. C. dubliniensis and C. albicans rely on interchangeable mechanisms to react to the ambient pH. Furthermore, pH-regulated expression of cell wall associated genes is closely linked to morphogenesis. Despite this, C. dubliniensis is not only less virulent than C. albicans but also displays a distinct epidemiology characterized by a preference for oropharyngeal colonialization and infection of HIV-positive patients. To reveal the reasons for this, reliable identification of C. dubliniensis is necessary. For that purpose, a rapid PCR test is introduced together with an evaluation of currently available phenotypic methods. Thoroughly characterized isolates of both species are available for further studies. KW - Candida KW - albicans KW - dubliniensis KW - pH KW - PHR KW - CdPHR KW - RIM101 KW - Zellwand KW - Candida KW - albicans KW - dubliniensis KW - pH KW - PHR KW - CdPHR KW - RIM10 KW - cell wall Y1 - 2001 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-1182281 ER -