Ecology and physiology of the emerging opportunistic fungi Pseudallescheria boydii and Scedosporium prolificans

Anaerobic growth and drug susceptibility of versatile fungal pathogen Scedosporium apiospermum

Although severe cases of invasive mycoses of different hypoxic and anoxic body parts have been reported, growth and drug susceptibility of fungal pathogens under anaerobic conditions remains understudied. The current study evaluated anaerobic growth potential and drug susceptibility of environmental Scedosporium apiospermum isolates under aerobic and anaerobic conditions. All tested strains showed equivalent growth and higher sensitivity to tested antifungal drugs under anaerobic conditions with lower minimum inhibitory concentration (MIC) as compared to aerobic conditions. Antifungal azoles were effective against isolates under both aerobic and anaerobic conditions. Most strains were resistant to antifungal echinocandins and polyenes under aerobic conditions but exhibited sensitivity under anaerobic conditions. This study provides evidence that resistance of S. apiospermum to antifungal drugs varies with oxygen concentration and availability and suggests re-evaluating clinical breakpoints for antifungal compounds to treat invasive fungal infections more effectively.

Extracellularly Released Molecules by the Multidrug-Resistant Fungal Pathogens Belonging to the Scedosporium Genus: An Overview Focused on Their Ecological Significance and Pathogenic Relevance

The multidrug-resistant species belonging to the Scedosporium genus are well recognized as saprophytic filamentous fungi found mainly in human impacted areas and that emerged as human pathogens in both immunocompetent and immunocompromised individuals. It is well recognized that some fungi are ubiquitous organisms that produce an enormous amount of extracellular molecules, including enzymes and secondary metabolites, as part of their basic physiology in order to satisfy their several biological processes. In this context, the molecules secreted by Scedosporium species are key weapons for successful colonization, nutrition and maintenance in both host and environmental sites. These biologically active released molecules have central relevance on fungal survival when colonizing ecological places contaminated with hydrocarbons, as well as during human infection, particularly contributing to the invasion/evasion of host cells and tissues, besides escaping from the cellular and humoral host immune responses. Based on these relevant premises, the present review compiled the published data reporting the main secreted molecules by Scedosporium species, which operate important physiopathological events associated with pathogenesis, diagnosis, antimicrobial activity and bioremediation of polluted environments.

Decoding the antifungal resistance mechanisms in biofilms of emerging, ubiquitous and multidrug-resistant species belonging to the Scedosporium/Lomentospora genera

The opportunistic filamentous fungi belonging to the Scedosporium and Lomentospora genera are highly tolerant to all classes of available antifungal drugs. Moreover, the mature biofilm formed by these fungi presents higher antifungal resistance when compared to planktonic cells. Nevertheless, the resistance mechanisms developed by the biofilm lifestyle are not completely elucidated. In the current study, we have investigated the mainly known resistance mechanisms to azoles (voriconazole and fluconazole) and polyenes (amphotericin B - AMB) in S. apiospermum, S. minutisporum, S. aurantiacum, and L. prolificans (formerly S. prolificans) biofilms. Both classes of antifungals can physically bind to the extracellular matrix of mature biofilms, preventing the drugs from reaching their targets on biofilm-forming cells, which precludes their activity and toxicity. In addition, the activity of efflux pumps, measured by Rhodamine 6 G, was increased along the maturation of the biofilm. The efflux pump's inhibition by L-Phe-L-Arg-β-naphthylamide culminated in a 2- to 16-fold increase in azole susceptibility in conidial cells, but not in mature biofilms. Finally, we demonstrated by using specific inhibitors that in conidia, but not in biofilms, AMB induced the production of reactive oxygen species through the activity of the oxidative phosphorylation system (complex I to IV and alternative oxidases). However, the cellular redox imbalance caused by AMB was well coped with the high activity of antioxidative enzymes, such as superoxide dismutase and catalase. Altogether, our results revealed that Scedosporium/Lomentospora biofilm resistance occurs through various mechanisms that operate concomitantly, which could explain the huge challenge in the clinical treatment of scedosporiosis/lomentosporiosis.

Lower Funneling Pathways in Scedosporium Species

Lignin, a natural polyaromatic macromolecule, represents an essential component of the lignocellulose biomass. Due to its complexity, the natural degradation of this molecule by microorganisms still remains largely misunderstood. Extracellular oxidative degradation is followed by intracellular metabolic degradation of conserved aromatic intermediate compounds (protocatechuate, catechol, hydroxyquinol, and gentisic acid) that are used as carbon and energy sources. The lower funneling pathways are characterized by the opening of the aromatic ring of these molecules through dioxygenases, leading to degradation products that finally enter into the tricarboxylic acid (TCA) cycle. In order to better understand the adaptation mechanisms of Scedosporium species to their environment, these specific catabolism pathways were studied. Genes encoding ring-cleaving dioxygenases were identified in Scedosporium genomes by sequence homology, and a bioinformatic analysis of the organization of the corresponding gene clusters was performed. In addition, these predictions were confirmed by evaluation of the expression level of the genes of the gentisic acid cluster. When the fungus was cultivated in the presence of lignin or gentisic acid as sole carbon source, experiments revealed that the genes of the gentisic acid cluster were markedly overexpressed in the two Scedosporium species analyzed (Scedosporium apiospermum and Scedosporium aurantiacum). Only the gene encoding a membrane transporter was not overexpressed in the gentisic acid-containing medium. Together, these data suggest the involvement of the lower funneling pathways in Scedosporium adaptation to their environment.

Fungal Community and Biodeterioration Analysis of Hull Wood and Its Storage Environment of the Nanhai No. 1 Shipwreck

The Nanhai No. 1 shipwreck is a Chinese merchant ship in the Southern Song Dynasty, and now it is stored in a huge enclosed glass warehouse in Maritime Silk Road Museum in Guangdong Province. At present, the hull of the Nanhai No. 1 shipwreck is still being excavated, and a small part of the hull wood is soaked in a specific solution to desalt. Through long-term exploration, we found that the above two states of hull wood had undergone biodeterioration, so the purpose of this study is to analyze the fungal community of exposed and soaked wood from the Nanhai No. 1 shipwreck. We sampled 10 exposed hull wood and sea mud samples, two wood storage water samples, and air samples in the glass warehouse. We used scanning electron microscope and optical microscope to find that there were obvious fungal structures in exposed wood and wood storing water samples. High-throughput sequencing of fungi revealed that the most abundant genera in exposed and soaked wood were Fusarium sp., and Scedosporium sp., respectively. In addition, Fusarium solani and Scedosporium apiospermum were successfully isolated from the hull wood surface and wood storing water samples, and the degradation tests of lignin and cellulose, the sensitivity tests of biocides and growth curve assay were carried out. We also found that Penicillium sp. and Cladosporium sp. are the most abundant in the glass warehouse air. Our research results show that F. solani and S. apiospermum should be regarded as a major threat to the preservation of the Nanhai No. 1 shipwreck. These results provide a reference for our protection of shipwrecks and other similar artifacts.

Tryptophol Coating Reduces Catheter-Related Cerebral and Pulmonary Infections by Scedosporium apiospermum

Introduction

Central venous catheter (CVC) is a medical device that is used to administer medication for a long duration. Colonization by an emerging opportunistic pathogen Scedosporium apiospermum in the CVC lumen is frequently reported to cause severe complications in patients. Here, we describe the effect of fungal quorum-sensing molecule (QSM) known as tryptophol (TOH) to control S. apiospermum colonization in catheter tube lumens in both in vitro and in vivo models.

Methods

Antifungal susceptibility of TOH against S. apiospermum was compared with voriconazole, and the colony diameter was determined on days 2, 4, and 6. Experimental catheterization rat model was conducted with pre-coating of TOH and voriconazole or an uncoated control and an infection with S. apiospermum. Biofilm formation on the catheter luminal surface was assessed using the scanning electron microscopy, crystal violet, and 2,3-bis(2-methoxy-4-ni-tro-5-sulfophenyl)-5-(phenylamino)-carbonyl-2H-tetra-zolium hydroxide (XTT) reduction assays. Brain and lung samples of catheterized rats were histopathologically assessed. Serum samples from catheterized rats were injected into Galleria mellonella larvae. Survival of catheterized rats and G. mellonella was determined.

Results

TOH impeded the growth of S. apiospermum by reducing the colony diameter in a dose-dependent manner. TOH coating remarkably lessened S. apiospermum biofilm formation and fungal cell viability on the catheter luminal surface. Additionally, TOH coating lessens cerebral edema that is associated with abscess and invasive pulmonary damages due to S. apiospermum catheter-related infection. Furthermore, TOH coating also lessened the virulence of S. apiospermum in sera of experimental catheterized rats and extended the survival rate of larvae Galleria mellonella infection model.

Conclusion

An alternative modification of catheter by coating with TOH is effective in preventing S. apiospermum colonization in vivo. Our study gives a new strategy to control catheter contamination and prevents nosocomial diseases due to S. apiospermum infection.

Growth and protease secretion of Scedosporium aurantiacum under conditions of hypoxia

One of the micro-environmental stresses that fungal pathogens, such as Scedosporium aurantiacum, colonising human lungs encounter in vivo is hypoxia, or deficiency of oxygen. In this work, we studied the impacts of a hypoxic micro-environment (oxygen levels ≤1%) on the growth of a clinical S. aurantiacum isolate (WM 06.482; CBS 136046) and an environmental strain (S. aurantiacum WM 10.136; CBS 136049) on mucin-containing synthetic cystic fibrosis sputum medium. Additionally, profiles of secreted proteases were compared between the two isolates and protease activity was assessed using class-specific substrates and inhibitors. Overall, both isolates grew slower and produced less biomass under hypoxia compared to normoxic conditions. The pH of the medium decreased to 4.0 over the cultivation time, indicating that S. aurantiacum released acidic compounds into the medium. Accordingly, secreted proteases of the two isolates were dominated by acidic proteases, including aspartic and cysteine proteases, with optimal protease activity at pH 4.0 and 6.0 respectively. The clinical isolate produced higher aspartic and cysteine protease activities. Conversely, all serine proteases, including elastase-like, trypsin-like, chymotrypsin-like and subtilisin-like proteases had higher activities in the environmental isolate. Sequence similarities to 13 secreted proteases were identified by mass spectrometry (MS) by searching against other fungal proteases in the NCBI database. Results from MS analysis were consistent with those from activity assays. The clinical highly-virulent, and environmental low-virulence S. aurantiacum isolates responded differently to hypoxia in terms of the type of proteases secreted, which may reflect their different virulence properties.

The genomic study of an environmental isolate of Scedosporium apiospermum shows its metabolic potential to degrade hydrocarbons

Crude oil contamination of soils and waters is a worldwide problem, which has been actively addressed in recent years. Sequencing genomes of microorganisms involved in the degradation of hydrocarbons have allowed the identification of several promoters, genes, and degradation pathways of these contaminants. This knowledge allows a better understanding of the functional dynamics of microbial degradation. Here, we report a first draft of the 44.2 Mbp genome assembly of an environmental strain of the fungus Scedosporium apiospermum. The assembly consisted of 178 high-quality DNA scaffolds with 1.93% of sequence repeats identified. A total of 11,195 protein-coding genes were predicted including a diverse group of gene families involved in hydrocarbon degradation pathways like dioxygenases and cytochrome P450. The metabolic pathways identified in the genome can potentially degrade hydrocarbons like chloroalkane/alkene, chorocyclohexane, and chlorobenzene, benzoate, aminobenzoate, fluorobenzoate, toluene, caprolactam, geraniol, naphthalene, styrene, atrazine, dioxin, xylene, ethylbenzene, and polycyclic aromatic hydrocarbons. The comparison analysis between this strain and the previous sequenced clinical strain showed important differences in terms of annotated genes involved in the hydrocarbon degradation process.

Advances in Fungal Phylogenomics and Their Impact on Fungal Systematics

In the past decade, advances in next-generation sequencing technologies and bioinformatic pipelines for phylogenomic analysis have led to remarkable progress in fungal systematics and taxonomy. A number of long-standing questions have been addressed using comparative analysis of genome sequence data, resulting in robust multigene phylogenies. These have added to, and often surpassed traditional morphology or single-gene phylogenetic methods. In this chapter, we provide a brief history of fungal systematics and highlight some examples to demonstrate the impact of phylogenomics on this field. We conclude by discussing some of the challenges and promises in fungal biology posed by the ongoing genomics revolution.

Merits and pitfalls of currently used diagnostic tools in mycetoma

Treatment of mycetoma depends on the causative organism and since many organisms, both actinomycetes (actinomycetoma) and fungi (eumycetoma), are capable of producing mycetoma, an accurate diagnosis is crucial. Currently, multiple diagnostic tools are used to determine the extent of infections and to identify the causative agents of mycetoma. These include various imaging, cytological, histopathological, serological, and culture techniques; phenotypic characterisation; and molecular diagnostics. In this review, we summarize these techniques and identify their merits and pitfalls in the identification of the causative agents of mycetoma and the extent of the disease. We also emphasize the fact that there is no ideal diagnostic tool available to identify the causative agents and that future research should focus on the development of new and reliable diagnostic tools.

Molecular identification tools for sibling species of Scedosporium and Pseudallescheria

The aim of this study was to develop molecular identification tools for currently recognized species of Pseudallescheria and Scedosporium through the use of species-specific primers and RFLP, so as to enhance rapid differentiation of clinically relevant species. The variability of species was established in a set of 681 Internal Transcribed Spacer (ITS) and 349 ß-tubulin (BT2) sequences. Amplified Fragment Length Polymorphism profile clustering matched with BT2 results, whereas ITS grouping was less detailed. ITS was sufficient for the differentiation of most haplotypes of clinically relevant species (P. apiosperma, P. boydii, S. aurantiacum, S. dehoogii, and S. prolificans) and of environmental species (P. minutispora and Lophotrichus fimeti) when Restriction Fragment Length Polymorphism (RFLP) were applied. For the identification of P. apiosperma and P. boydii species-specific BT2 primers were needed. Pseudallescheria fusoidea, P. ellipsoidea and P. angusta remained difficult to distinguish from P. boydii.

Infections due to Pseudallescheria/Scedosporium species in patients with advanced HIV disease--a diagnostic and therapeutic challenge

OBJECTIVES

The aim of this study is to highlight the importance of infections caused by members of the genera Pseudallescheria/Scedosporium in HIV-positive patients.

METHODS

We describe a case of a fatal scedosporiosis in a treatment-naïve HIV patient and review all previously reported cases of pseudallescheriosis/scedosporiosis from a search of the PubMed and Deutsches Institut für Medizinische Dokumentation und Information (DIMDI) databases, applying the terms 'Pseudallescheria', 'Scedosporium', 'Allescheria', 'Monosporium', 'Petriellidium', 'boydii', 'prolificans', 'inflatum', cross-referenced with 'HIV' and 'AIDS'.

RESULTS

Detection of Scedosporium and Pseudallescheria species has been reported in 22 HIV-positive patients. Fourteen isolates belonged to the Pseudallescheria boydii complex and eight to Scedosporium prolificans. Invasive scedosporiosis (IS) was proven in 54.5% of the patients. Among them dissemination was observed in 66.7%. Pseudallescheria/Scedosporium species were mainly isolated from male individuals. Patients with proven IS showed CD4+ cell counts <100/μl and a higher co-infection rate as compared to colonized patients. Patients with central nervous system (CNS) manifestations showed CD4+ cell counts <50/μl. The mortality rate for patients with proven IS was 75% and was 100% for patients with dissemination/CNS manifestations. The fatality rate for patients treated with antifungal drugs plus surgery was lower compared to patients treated with antimycotic agents alone.

CONCLUSIONS

IS only occurred in HIV-positive patients with a strongly impaired immune system. The survival rates of patients with advanced HIV disease and invasive scedosporiosis can be improved by rapid diagnosis by biopsy and requires complex therapy with a combination of active antifungal drugs, surgery and supportive immune augmentation.

Molecular phylogeny and proposal of two new species of the emerging pathogenic fungus Saksenaea

Saksenaea is a monotypic genus belonging to the order Mucorales and capable of producing severe human infections. Through a polyphasic study based on analysis of the sequences of the internal transcribed spacer (ITS) region, domains D1 and D2 of the 28S rRNA gene, and the elongation factor 1α (EF-1α) gene, as well as by evaluation of relevant morphological and physiological characteristics of a set of clinical and environmental strains, we have demonstrated that Saksenaea vasiformis is a complex of species. We propose as new species Saksenaea oblongispora, characterized by oblong sporangiospores and unable to grow at 42°C, and Saksenaea erythrospora, characterized by large sporangiophores and sporangia and by ellipsoid sporangiospores, biconcave in the lateral view. Itraconazole, posaconazole, and terbinafine were active against all isolates included in the study, while amphotericin B, voriconazole, and the echinocandins showed low activity.

Epidemiology of Acute Respiratory Failure in Patients with HM (ICU Only)

Pulmonary complications are common in hematological patients, particularly those receiving a hematological stem cell transplant (HSCT), and a significant percentage of them will require intensive care unit (ICU) admission. Acute respiratory failure in these patients is a threatening event, with a very poor outcome, particularly when mechanical ventilation (MV) is required. For many years, oncologists and intensivists had a pessimistic vision of the dismal outcome of those hematological patients requiring admission to the ICU. The bleak experience in this population led some authors to suggest early withdrawal of support, or even withholding the option of mechanical ventilation altogether. However, over the last years this vision seems to be changing. Great progress has been made in stem cell transplantation that can be ascribed to a better understanding of the human leukocyte antigen (HLA) system for donor selection, more effective and less toxic immunosupression for prevention and treatment of graft-versus host disease (GVHD), and significant advances in infectious disease therapy. Also improvements in ventilatory and supportive care, such as the early implantation of noninvasive ventilation (NIV), may avoid intubation in a significant percentage of patients suffering from acute respiratory failure. As a result of all this, the proportion of both hematological patients requiring management in the ICU and those requiring MV is decreasing. Also the survival rate of HSCT recipients admitted to the ICU has been steadily improving. In this chapter we will report on the epidemiology of acute respiratory failure in patients with hematological malignancies.

The changing microbial epidemiology in cystic fibrosis

Infection of the airways remains the primary cause of morbidity and mortality in persons with cystic fibrosis (CF). This review describes salient features of the epidemiologies of microbial species that are involved in respiratory tract infection in CF. The apparently expanding spectrum of species causing infection in CF and recent changes in the incidences and prevalences of infection due to specific bacterial, fungal, and viral species are described. The challenges inherent in tracking and interpreting rates of infection in this patient population are discussed.

Osteomyelitis and discospondylitis due to Scedosporium apiospermum in a dog

A 6-year-old, 30-kg, female German Shepherd Dog, living in a leishmaniasis enzootic area, was presented with a severe rear limb motor disorder and a medical history of acute onset of fever. Routine hematology indicated neutrophilia. Spinal survey radiographs were consistent with osteomyelitis and discospondylitis. Because of the poor clinical prognosis and the painful nature of the lesions, the dog was euthanized at the owners' request. At necropsy, T13-L1 vertebrae had large areas of necrosis within the vertebral bodies. Histopathological findings were consistent with chronic, severe, fungal osteomyelitis and discospondylitis. Polymerase chain reaction identified Scedosporium apiospermum, a eutrophic filamentous fungus now recognized as an emerging agent of severe infections in immunosuppressed human patients.

Tracking the emerging human pathogen Pseudallescheria boydii by using highly specific monoclonal antibodies

Pseudallescheria boydii has long been known to cause white grain mycetoma in immunocompetent humans, but it has recently emerged as an opportunistic pathogen of humans, causing potentially fatal invasive infections in immunocompromised individuals and evacuees of natural disasters, such as tsunamis and hurricanes. The diagnosis of P. boydii is problematic since it exhibits morphological characteristics similar to those of other hyaline fungi that cause infectious diseases, such as Aspergillus fumigatus and Scedosporium prolificans. This paper describes the development of immunoglobulin M (IgM) and IgG1 kappa-light chain monoclonal antibodies (MAbs) specific to P. boydii and certain closely related fungi. The MAbs bind to an immunodominant carbohydrate epitope on an extracellular 120-kDa antigen present in the spore and hyphal cell walls of P. boydii and Scedosporium apiospermum. The MAbs do not react with S. prolificans, Scedosporium dehoogii, or a large number of clinically relevant fungi, including A. fumigatus, Candida albicans, Cryptococcus neoformans, Fusarium solani, and Rhizopus oryzae. The MAbs were used in immunofluorescence and double-antibody sandwich enzyme-linked immunosorbent assays (DAS-ELISAs) to accurately differentiate P. boydii from other infectious fungi and to track the pathogen in environmental samples. Specificity of the DAS-ELISA was confirmed by sequencing of the internally transcribed spacer 1 (ITS1)-5.8S-ITS2 rRNA-encoding regions of environmental isolates.

Infections caused by Scedosporium spp

Scedosporium spp. are increasingly recognized as causes of resistant life-threatening infections in immunocompromised patients. Scedosporium spp. also cause a wide spectrum of conditions, including mycetoma, saprobic involvement and colonization of the airways, sinopulmonary infections, extrapulmonary localized infections, and disseminated infections. Invasive scedosporium infections are also associated with central nervous infection following near-drowning accidents. The most common sites of infection are the lungs, sinuses, bones, joints, eyes, and brain. Scedosporium apiospermum and Scedosporium prolificans are the two principal medically important species of this genus. Pseudallescheria boydii, the teleomorph of S. apiospermum, is recognized by the presence of cleistothecia. Recent advances in molecular taxonomy have advanced the understanding of the genus Scedosporium and have demonstrated a wider range of species than heretofore recognized. Studies of the pathogenesis of and immune response to Scedosporium spp. underscore the importance of innate host defenses in protection against these organisms. Microbiological diagnosis of Scedosporium spp. currently depends upon culture and morphological characterization. Molecular tools for clinical microbiological detection of Scedosporium spp. are currently investigational. Infections caused by S. apiospermum and P. boydii in patients and animals may respond to antifungal triazoles. By comparison, infections caused by S. prolificans seldom respond to medical therapy alone. Surgery and reversal of immunosuppression may be the only effective therapeutic options for infections caused by S. prolificans.

Molecular typing of Australian Scedosporium isolates showing genetic variability and numerous S. aurantiacum

One hundred clinical isolates from a prospective nationwide study of scedosporiosis in Australia (2003-2005) and 46 additional isolates were genotyped by internal transcribed spacer-restriction fragment length polymorphism (ITS-RFLP) analysis, ITS sequencing, and M13 PCR fingerprinting. ITS-RFLP and PCR fingerprinting identified 3 distinct genetic groups. The first group corresponded to Scedosporium prolificans (n = 83), and the other 2 comprised isolates previously identified as S. apiospermum: one of these corresponded to S. apiospermum (n = 33) and the other to the newly described species S. aurantiacum (n = 30). Intraspecies variation was highest for S. apiospermum (58%), followed by S. prolificans (45%) and S. aurantiacum (28%) as determined by PCR fingerprinting. ITS sequence variation of 2.2% was observed among S. apiospermum isolates. No correlation was found between genotype of strains and their geographic origin, body site from which they were cultured, or colonization versus invasive disease. Twelve S. prolificans isolates from 2 suspected case clusters were examined by amplified fragment length polymorphism analysis. No specific clusters were confirmed.

Fungal Infections

The incidence of invasive fungal infections has increased dramatically over the past two decades, mostly due to an increase in the number of immunocompromised patients.1–4 Patients who undergo chemotherapy for a variety of diseases, patients with organ transplants, and patients with the acquired immune deficiency syndrome have contributed most to the increase in fungal infections.5 The actual incidence of invasive fungal infections in transplant patients ranges from 15% to 25% in bone marrow transplant recipients to 5% to 42% in solid organ transplant recipients.6,7 The most frequently encountered are Aspergillus species, followed by Cryptococcus and Candida species. Fungal infections are also associated with a higher mortality than either bacterial or viral infections in these patient populations. This is because of the limited number of available therapies, dose-limiting toxicities of the antifungal drugs, fewer symptoms due to lack of inflammatory response, and the lack of sensitive tests to aid in the diagnosis of invasive fungal infections.1 A study of patients with fungal infections admitted to a university-affiliated hospital indicated that community-acquired infections are becoming a serious problem; 67% of the 140 patients had community-acquired fungal pneumonia.8

Sporothrix brasiliensis, S. globosa, and S. mexicana, three new Sporothrix species of clinical interest

Sporothrix schenckii is the species responsible for sporotrichosis, a fungal infection caused by the traumatic implantation of this dimorphic fungus. Recent molecular studies have demonstrated that this species constitutes a complex of numerous phylogenetic species. Since the delineation of such species could be of extreme importance from a clinical point of view, we have studied a total of 127 isolates, most of which were received as S. schenckii, including the available type strains of species currently considered synonyms, and also some close morphological species. We have phenotypically characterized all these isolates using different culture media, growth rates at different temperatures, and numerous nutritional tests and compared their calmodulin gene sequences. The molecular analysis revealed that Sporothrix albicans, S. inflata, and S. schenckii var. luriei are species that are clearly different from S. schenckii. The combination of these phenetic and genetic approaches allowed us to propose the new species Sporothrix brasiliensis, S. globosa, and S. mexicana. The key phenotypic features for recognizing these species are the morphology of the sessile pigmented conidia, growth at 30, 35, and 37 degrees C, and the assimilation of sucrose, raffinose, and ribitol.

Pseudallescheriasis in the 21st century

Since its discovery as an agent of mycetoma nearly a century ago, Pseudallescheria boydii with its asexual (synanamorphic) form, Scedosporium apiospermum, is now recognized as an important emerging opportunistic pathogen causing invasive mycosis in immunocompromised patients. The clinical spectrum of pseudallescheriasis is wide. Invasive disease of the lung, CNS and dissemination are serious manifestations in immunocompromised patients. This organism responds poorly to amphotericin B, and its histopathologic resemblance to aspergillosis often results in a delay in diagnosis. In vitro data, animal models and accumulating clinical experience support the use of voriconazole as a primary treatment for pseudallescheriasis. This paper reviews the microbiology, ecology, epidemiologic trends, clinical manifestations and current treatment options of pseudallescheriasis.

Molecular taxonomy and ecology of Pseudallescheria, Petriella and Scedosporium prolificans (Microascaceae) containing opportunistic agents on humans

The main purpose of the present paper is to establish the connection between phylogenetic and morphological data and ecological features of strains of Pseudallescheria, Petriella, and Scedosporium. For the phylogenetic analysis sequences of the ITS region and the large subunit (partial sequences) of the rDNA were used. Cultural characteristics were observed on MEA 2 % and Weitzman-Silva Hutner Agar. Results showed, that three major groups could be differentiated, corresponding to Pseudallescheria, Petriella and S. prolificans. Among Petriella species only Pe. setifera is reasonably delimited. Pe. musispora was found to be synonymous with Pe. setifera. S. prolificans proved to be a homogenous species on the basis of ITS-sequences. Morphologically, Pseudallescheria and Petriella are distinguished by ostiolate vs non-ostiolate ascomata, a bipartition reflected also in ITS sequence data. We hypothesise a secondary loss of the ostiole of Pseudallescheria due to its ecological preferences. Infraspecific grouping within the highly variable species P. boydii is consistent for at least one clade in the ITS tree. The evolution of lineages with increased virulence within P. boydii is discussed.

Efficacy of albaconazole (UR-9825) in treatment of disseminated Scedosporium prolificans infection in rabbits

There are no effective therapeutics for treating invasive Scedosporium prolificans infections. Doses of 15, 25, and 50 mg/kg of body weight/day for the new triazole albaconazole (ABC) were evaluated in an immunocompetent rabbit model of systemic infection with this mold. Treatments were begun 1 day after challenge and given for 10 days. ABC at any dose was more effective than amphotericin B (AMB) at 0.8 mg/kg/day at clearing S. prolificans from tissue (P < 0.007). The percentages of survival at 25 mg of ABC/kg/day were similar to those obtained with AMB. Rabbits showed 100% survival when they were treated with 50 mg of ABC per kg (P < 0.0001 versus control group), and only this dosage was able to reduce tissue burden significantly in the five organs studied, i.e., spleen, kidneys, liver, lungs, and brain.

Disseminated Pseudallescheria boydii (Scedosporium apiospermum) infection in a renal transplant patient

Transplant recipients receive a number of immunosuppressive medications that result in an increased risk of infection, including infections with microbes that are normally not pathogenic. We describe a patient with end-stage renal disease who underwent kidney transplantation. Six months postoperatively, he presented with a lesion on his ankle, multiple thigh nodules, and right testicular pain. Biopsy of the ankle lesion demonstrated Pseudallescheria boydii (Scedosporium apiospermum), a common environmental fungus. Following orchiectomy, multiple fungal elements were found that were initially described as Aspergillus species, but later identified as P. boydii. In addition, multiple brain abscesses were found on magnetic resonance imaging. Despite treatment with multiple antifungal medications, the patient died of cardiac dysrhythmia. Current diagnostic and therapeutic alternatives for P. boydii are reviewed.

An immunocompetent patient with primary Scedosporium apiospermum vertebral osteomyelitis

Scedosporium apiospermum, the asexual anamorph of Pseudallescheria boydii, is a ubiquitous saprophytic fungus that usually causes cutaneous/subcutaneous infection but may manifest as an invasive disease, often in immunocompromised hosts. Following an extensive literature review, we think that this case represents the first documented report of a primary infection of the spine in an immunocompetent patient. Despite extensive surgical debridement and itraconazole therapy, the patient died of multisystem organ failure of unknown etiology. Our case and three previously reported cases of P. boydii vertebral osteomyelitis highlight the importance of obtaining repeat cultures in patients with culture-negative vertebral osteomyelitis who fail to adequately respond to empiric standard antibacterial and/or antimycobacterial therapy. Combined surgical debridement and antifungal therapy have been required for eradication of P. boydii spinal infections in two previously reported immunocompromised patients, although the optimal antifungal regimen for this infection has not been established.

Fungal keratitis caused by Scedosporium apiospermum: report of two cases and review of treatment

PURPOSE

We report our experience in treating two cases of Scedosporium apiospermum keratitis and provide a review of basic scientific and clinical data regarding the treatment of this visually devastating disease.

METHOD

We present a case report and literature review.

RESULTS

A 35-year-old woman and a 73-year-old man both reported pain, redness, and a foreign body sensation in the eye after trauma. They were initially treated with antibacterials. When cultures were positive for S. apiospermum, the first patient was treated with fluconazole and amphotericin with good results. The second was treated with fluconazole and natamycin, but the infection persisted and the eye was eventually enucleated. Review of the literature showed variable responsiveness of S. apiospermum to antifungal treatment.

CONCLUSIONS

It is difficult to predict how S. apiospermum keratitis will respond to treatment, but miconazole appears to be useful in conjunction with other antifungals. Voriconazole shows promise as an effective alternative.

Fungal flora in groundwater-derived public drinking water

In order to assess the dissemination of hygienically relevant fungi via the public drinking water distribution system, a 12-month survey was performed on groundwater-derived drinking water from 29 water supplies in North Rhine-Westphalia, Germany. Frequencies of contaminated water samples, and the prevalent species and patterns of occurrence in raw water, waterworks, the network and house installations were studied on the basis of 2657 water samples. Results were obtained by long-term incubation of 1 ml aliquots of water samples on agar-based culture media, following bacteriological procedures documented in the German drinking water regulations (Anon, 1990). No correlation with standard hygiene indicators, such as E. coli or other coliform bacteria was observed. Common opportunistic and allergenic Aspergillus species were encountered only rarely. The fungal flora was dominated by a limited number of species of Acremonium, Exophiala, Penicillium and particularly Phialophora; some of them occurred throughout the entire drinking water system and are thought to constitute a resident fungal flora. Phialophora sp. nov., to be described as a new species elsewhere, was ubiquitous; it was found in 26.6% of the samples positive for fungi (7.5% of 2657). Fungal diversity in the network itself was significantly lower than in raw water and house installations, indicating that not all fungi gaining access to the system are capable of surviving for longer periods. For species such as Verticillium lecanii, found exclusively after the introduction of newly buried pipes and remaining localized at those sites, introduction via arthropod vectors is likely. The resident species of Phialophora, Exophiala and Acremonium are particularly significant as they are shown to be disseminated efficiently by public drinking water.

Environmental occurrence of Madurella mycetomatis, the major agent of human eumycetoma in Sudan

Madurella mycetomatis is the main causative agent of human eumycetoma, a severe debilitating disease endemic in Sudan. It has been suggested that eumycetoma has a soil-borne or thorn prick-mediated origin. For this reason, efforts were undertaken to culture M. mycetomatis from soil samples (n = 43) and thorn collections (n = 35) derived from areas in which it is endemic. However, ribosomal sequencing data revealed that the black fungi obtained all belonged to other fungal species. In addition, we performed PCR-mediated detection followed by restriction fragment length polymorphism (RFLP) analysis for the identification of M. mycetomatis DNA from the environmental samples as well as biopsies from patients with mycetoma. In the case of the Sudanese soil samples, 17 out of 74 (23%) samples were positive for M. mycetomatis DNA. Among the thorn collections, 1 out of 22 (5%) was positive in the PCR. All PCR RFLP patterns clearly indicated the presence of M. mycetomatis. In contrast, 15 Dutch and English control soil samples were all negative. Clinically and environmentally obtained fungal PCR products share the same PCR RFLP patterns, suggesting identity, at least at the species level. These observations support the hypothesis that eumycetoma is primarily environmentally acquired and suggest that M. mycetomatis needs special conditions for growth, as direct isolation from the environment seems to be impossible.

Scedosporium prolificans keratouveitis in association with a contact lens retained intraocularly over a long term

Scedosporium prolificans is a soil saprophyte that is associated with a large variety of infectious processes and with respiratory colonization in immunocompetent and immunocompromised patients. We report the first described case of S. prolificans keratouveitis associated with the intraocular long-term retention of a contact lens in a 76-year-old female patient.

Electrotransformation of the human pathogenic fungus Scedosporium prolificans mediated by repetitive rDNA sequences

The regions encoding the 5.8S rRNA and the flanking internal transcribed spacers (ITSI and ITSII) from two isolates of the human pathogenic fungus Scedosporium prolificans and one isolate of the taxonomically related species Pseudallescheria boydii (S. apiospermum) were sequenced. The sequences of the two S. prolificans isolates were identical. However, there were minor differences between both species. Phylogenetic analysis of known fungal sequences confirmed a close relationship between S. prolificans and P. boydii. An attempt was made to transform S. prolificans by electroporation using a plasmid vector, pMLF2, bearing the Escherichia coli hygromycin B phosphotransferase gene (hph) under the control of Aspergillus nidulans promoter and terminator sequences. To increase transformation efficiency, the sequenced ribosomal cluster of S. prolificans was used to construct a new vector for homologous recombination.

Acquisition, transport, and storage of iron by pathogenic fungi

Iron is required by most living systems. A great variety of means of acquisition, avenues of uptake, and methods of storage are used by pathogenic fungi to ensure a supply of the essential metal. Solubilization of insoluble iron polymers is the first step in iron assimilation. The two methods most commonly used by microorganisms for solubilization of iron are reduction and chelation. Reduction of ferric iron to ferrous iron by enzymatic or nonenzymatic means is a common mechanism among pathogenic yeasts. Under conditions of iron starvation, many fungi synthesize iron chelators known as siderophores. Two classes of compounds that function in iron gathering are commonly observed: hydroxamates and polycarboxylates. Two major responses to iron stress in fungi are a high-affinity ferric iron reductase and siderophore synthesis. Regulation of these two mechanisms at the molecular level has received attention. Uptake of siderophores is a diverse process, which varies among the different classes of compounds. Since free iron is toxic, it must be stored for further metabolic use. Polyphosphates, ferritins, and siderophores themselves have been described as storage molecules. The iron-gathering mechanisms used by a pathogen in an infected host are largely unknown and can only be posited on the basis of in vitro studies at present.

Peritonitis by scedosporium apiospermum in a patient undergoing continuous ambulatory peritoneal dialysis

A case of peritonitis due to Scedosporium apiospermum in a boy undergoing continuous ambulatory peritoneal dialysis is reported. The finding of suggestive tissual form of the fungus in the effluent hastened the diagnosis of the infection.

Comparative in-vitro activity of voriconazole (UK-109,496) and six other antifungal agents against clinical isolates of Scedosporium prolificans and Scedosporium apiospermum

We report the in-vitro susceptibility of 27 clinical isolates of Scedosporium apiospermum and 43 of Scedosporium prolificans. S. apiospermum was resistant to fluconazole and flucytosine, with variable susceptibility to amphotericin B, itraconazole, ketoconazole and susceptible to miconazole. Voriconazole was much more active than fluconazole and flucytosine, more active than amphotericin B, itraconazole and ketoconazole and was as active as miconazole against S. apiospermum isolates. Voriconazole and the other six antifungal agents showed low activity against S. prolificans isolates.

Subcutaneous scedosporiosis. Report of two cases and review of the literature

Two cases of subcutaneous scedosporiosis, caused by Scedosporium apiospermum, are reported. Both patients had lesions localized in the forearm: a solitary ulceration in one and a sporotrichoid-like lesion in the other. The literature is reviewed.

Disseminated mycosis due to Scedosporium prolificans in an AIDS patient with Burkitt lymphoma

A case of fatal disseminated infection caused by the dematiaceous hyphomycete Scedosporium prolificans diagnosed post mortem is reported in a 60-year-old male patient with acquired immunodeficiency syndrome who additionally suffered from Burkitt's lymphoma. The patient was significantly granulocytopenic following aggressive chemotherapy and irradiation. He developed dyspnoea at rest and chest pain despite a normal chest radiograph. Fluconazole treatment was carried out empirically because no sign of a fungal infection was detected ante mortem, either by mycological cultivation or by serological investigation. First post-mortem examination revealed a disseminated fungal infection involving the central nervous system. Scedosporium prolificans was cultured from the kidney, spleen and myocardium. In vitro, the fungal isolate was found to be highly resistant to all available systemic antimycotics.

Nosocomial outbreak caused by Scedosporium prolificans (inflatum): four fatal cases in leukemic patients

Four cases of fatal disseminated Scedosporium prolificans (inflatum) infection occurring in neutropenic patients are reported. Because of hospital renovation, the patients were cared for in a temporary hematologic facility. S. prolificans (inflatum) was isolated from blood cultures of these four patients, two of whom underwent full necropsy, and revealed abundant vegetative hyphae and ovoid conida with truncate bases in many organs. In vitro susceptibility testing of fungal strains showed all isolates to be resistant to amphotericin B, flucytosine, miconazole, ketoconazole, fluconazole, and itraconazole, with MICs greater than 16 micrograms/ml. The reported infections, two in each of two rooms, occurred over a period of 1 month, with very similar clinical outcomes. Circumstancial evidence suggested a nosocomial outbreak, but the environmental samples collected from the rooms, corridors, and adjacent areas did not yield S. prolificans (inflatum). Nevertheless, circumstantial evidence suggested a nosocomial outbreak of S. prolificans (inflatum) infection.

Arthritis without grains caused by Pseudallescheria boydii

Severe infection of the knee joint by Pseudallescheria boydii in a 23-year-old female resulted in complete destruction of the cartilaginous surface. The possibility of entry of the fungus through mild abrasions of unperforated skin is discussed. The clinical appearance is compared with that of Scedosporium prolificans. Antimycotic miconazole-itraconazole treatment, applied during a period of 4 months, was successful; no side-effects were noted.