Scedosporium species and Lomentospora prolificans fungaemia is uniformly fatal in patients with haematological malignancy

Scedosporium and Lomentospora species are environmental moulds that are virulent in immunocompromised hosts and rarely cause bloodstream infection (BSI). Patients with Scedosporium and Lomentospora species BSI were identified by the state public laboratory service in Queensland, Australia, over a 20-year period. Twenty-two incident episodes occurred among 21 residents; one patient had a second episode 321 days following the first. Of these, 18 were Lomentospora prolificans, three were Scedosporium apiospermum complex and one was a nonspeciated Scedosporium species. Seventeen (81%) patients died during their index admission, and all-cause mortality at 30, 90 and 365 days was 73%, 82% and 91% respectively. All 20 patients with haematological malignancy died within 365 days of follow-up with a median time to death of 9 days (interquartile range, 6-20 days) following diagnoses of BSI.

Scedosporium species in soils from various biomes in Northwestern Morocco

Scedosporium species are opportunistic pathogens causing various infections, including disseminated infections in severely immunocompromised patients. Preventive measures aiming to reduce the risk of exposure to these fungi require a better knowledge on their ecology and on the sources of contamination of the patients. In this context, 99 soil samples from the Rabat-Sale-Kenitra and Fez-Meknes regions in Morocco were analyzed. Samples were inoculated on the highly selective Scedo-Select III culture medium, and seven chemical parameters of the soils were measured. Scedosporium species were detected in 48 of the samples, with the highest density in soils from wastewater treatment plants and landfills, followed by those from roadsides and polluted riverbanks, thus confirming the impact of human activities on their ecology. Scedosporium apiospermum was the most common species, followed by S. boydii and S. aurantiacum. Analysis of the chemical parameters of the soils revealed the presence of Scedosporium species was mainly associated with a moderate electrical conductivity, a pH range of 7.0 to 7.6, a nutrient-rich content and a moderate phosphorus amount. Thereby, these results demonstrated the relatively high occurrence of Scedosporium in Morocco and highlighted the impact of phosphorus content on their ecology.

Distribution of Scedosporium species in soil from areas with high human population density and tourist popularity in six geographic regions in Thailand

Scedosporium is a genus comprising at least 10 species of airborne fungi (saprobes) that survive and grow on decaying organic matter. These fungi are found in high density in human-affected areas such as sewage-contaminated water, and five species, namely Scedosporium apiospermum, S. boydii, S. aurantiacum, S. dehoogii, and S. minutisporum, cause human infections. Thailand is a popular travel destination in the world, with many attractions present in densely populated areas; thus, large numbers of people may be exposed to pathogens present in these areas. We conducted a comprehensive survey of Scedosporium species in 350 soil samples obtained from 35 sites of high human population density and tourist popularity distributed over 23 provinces and six geographic regions of Thailand. Soil suspensions of each sample were inoculated on three plates of Scedo-Select III medium to isolate Scedosporium species. In total, 191 Scedosporium colonies were isolated from four provinces. The species were then identified using PCR and sequencing of the beta-tubulin (BT2) gene. Of the 191 isolates, 188 were S. apiospermum, one was S. dehoogii, and species of two could not be exactly identified. Genetic diversity analysis revealed high haplotype diversity of S. apiospermum. Soil is a major ecological niche for Scedosporium and may contain S. apiospermum populations with high genetic diversity. This study of Scedosporium distribution might encourage health care providers to consider Scedosporium infection in their patients.

Phenotypic profiling of Scedosporium aurantiacum, an opportunistic pathogen colonizing human lungs

Genotyping studies of Australian Scedosporium isolates have revealed the strong prevalence of a recently described species: Scedosporium aurantiacum. In addition to occurring in the environment, this fungus is also known to colonise the respiratory tracts of cystic fibrosis (CF) patients. A high throughput Phenotype Microarray (PM) analysis using 94 assorted substrates (sugars, amino acids, hexose-acids and carboxylic acids) was carried out for four isolates exhibiting different levels of virulence, determined using a Galleria mellonella infection model. A significant difference was observed in the substrate utilisation patterns of strains displaying differential virulence. For example, certain sugars such as sucrose (saccharose) were utilised only by low virulence strains whereas some sugar derivatives such as D-turanose promoted respiration only in the more virulent strains. Strains with a higher level of virulence also displayed flexibility and metabolic adaptability at two different temperature conditions tested (28 and 37°C). Phenotype microarray data were integrated with the whole-genome sequence data of S. aurantiacum to reconstruct a pathway map for the metabolism of selected substrates to further elucidate differences between the strains.

ScedosporiumSpecies Infections and Treatments

Scedosporium species are now increasingly isolated from immunocompromised and immunocompetent patients. Unfortunately, Scedosporium species infections are generally resistant to amphotericin B, and S. prolificans strains are particularly resistant to presently-available antifungal agents. Here we review the microbiology, expanding epidemiology, numerous clinical presentations, and diagnostic tools available for Scedosporium species infections. Finally, we detail the available in vitro, animal model, and clinical data on the treatment of Scedosporium species infections with special emphasis on the role of newer antifungal therapies for these recalcitrant infections.

Deep skin infection of Scedosporium apiospermum in a patient with refractory idiopathic thrombocytopenic purpura

Infection of Scedosporium apiospermum is very rare but is now emerging as an important cause of both localized and disseminated infections in immunocompromised patients. A 62-year-old woman, who had undergone steroid therapy for refractory idiopathic thrombocytopenic purpura and had a history of diffuse large B cell lymphoma, developed a deep skin ulcer complicated with lymphangitis. After culture study demonstrated the presence of S. apiospermum, voriconazole (VRCZ) was administered and prompt improvement was observed. Because it is difficult to distinguish S. apiospermum from Aspergillus by histopathology and S. apiospermum is resistant to amphotericin B, VRCZ should be selected as the first choice of antifungal agent when mold is considered to be the causative organism.

Monoclonal antibodies against peptidorhamnomannans of Scedosporium apiospermum enhance the pathogenicity of the fungus

Scedosporium apiospermum is part of the Pseudallescheria-Scedosporium complex. Peptidorhamnomannans (PRMs) are cell wall glycopeptides present in some fungi, and their structures have been characterized in S. apiospermum, S. prolificans and Sporothrix schenckii. Prior work shows that PRMs can interact with host cells and that the glycopeptides are antigenic. In the present study, three monoclonal antibodies (mAbs, IgG1) to S. apiospermum derived PRM were generated and their effects on S. apiospermum were examined in vitro and in vivo. The mAbs recognized a carbohydrate epitope on PRM. In culture, addition of the PRM mAbs increased S. apiospermum conidia germination and reduced conidial phagocytosis by J774.16 macrophages. In a murine infection model, mice treated with antibodies to PRM died prior to control animals. Thus, PRM is involved in morphogenesis and the binding of this glycopeptide by mAbs enhanced the virulence of the fungus. Further insights into the effects of these glycopeptides on the pathobiology of S. apiospermum may lead to new avenues for preventing and treating scedosporiosis.

The incidence of fungal infections has increased dramatically over the last 50 years, largely because of the increasing size of the population at risk, which especially includes immunocompromised hosts. Scedosporium apiospermum is a filamentous fungus that causes a variety of infections, ranging from localized disease to life-threatening disseminated infections. Glycoproteins are molecules present in the fungal surface and are comprised of carbohydrate and protein components. They are involved in different important functions in the fungal cell. Monoclonal antibodies can be used as therapeutic agents for infectious disease, but some factors involved in their efficacy are often not well understood. We found that monoclonal antibodies to glycoproteins present in fungal surface can be nonprotective and can even enhance the disease. The administration of these antibodies can affect functions of the fungal cell and the immune cells, resulting in a survival advantage for the fungus during interactions with the host.

Comparative virulence of Scedosporium species in animal models

Scedosporium species are an emerging opportunist group of fungi that have been found to cause infections in both immunocompetent and non-immunocompetent individuals. The infections are not regularly distributed among different countries of the world either because of improper identification or other geographical reasons. Strange as it may, disseminated systemic infections have only been reported in some specific countries. We used a mouse model of disseminated infection to assess if strains from Nigeria were virulent and compared it to a few other strains from other countries. S. apiospermum isolated from Nigeria were clearly less virulent than those obtained elsewhere. This may be the reason why this group of fungi has not been associated with specific clinical problems in Nigeria in particular and Africa in general.

[Scedosporium apiospermum brain abscess. Report of one case with literature review]

Scedosporium apiospermum is a fungus found in the soil and in contaminated water and commonly cause cutaneous infections and is a rare cause of central nervous system infection. Invasive infection is usually associated with immunosuppresion. The authors present a 73-year-old woman with chronic renal disease who presented with headache for 2 weeks. Computerized tomography scans revealed a ring-enhancing lesion in left temporal lobe. An urgent craniotomy was performed and the lesion was totally removed. The patient died 5 days later. Scedosporium apiospermum was isolated in the culture of the extirpated lesion. The authors review the previously reported cases of brain abscess for Scedosporium apiospermum.

Scedosporium prolificans brain abscess in a patient with chronic granulomatous disease: Successful combination therapy with voriconazole and terbinafine

A patient with chronic granulomatous disease developed brain abscesses with Scedosporium prolificans. In vitro susceptibility revealed a synergistic effect of terbinafine and voriconazole. He received therapy with both these antifungals which resulted in disappearance of the brain abscesses. This is the first reported cure of a CNS S. prolificans infection in an immunocompromised host.

Multifocal Scedosporium apiospermum spondylitis in a cystic fibrosis patient

We report the first case of multifocal Scedosporium apiospermum spondylitis in a cystic fibrosis patient. The infection, which occurred during voriconazole prophylaxis, disseminated contiguously from the base of the left lung and pleura and spread to vertebrae via the epidural space. S. apiospermum osteoarticular infections are rare, and are difficult to diagnose and cure because of their resistance to anti-fungal drugs.

The opportunistic fungal pathogen Scedosporium prolificans: carbohydrate epitopes of its glycoproteins

Isolated from the mycelium of Scedosporium prolificans were complex glycoproteins (RMP-Sp), with three structurally related components (HPSEC). RMP-Sp contained 35% protein and 62% carbohydrate with Rha, Ara, Man, Gal, Glc, and GlcNH(2) in a 18:1:24:8:6:5 molar ratio. Methylation analysis showed mainly nonreducing end- of Galp (13%), nonreducing end- (9%), 2-O- (13%), and 3-O-subst. Rhap (7%), nonreducing end- (11%), 2-O- (10%), 3-O- (14%), and 2,6-di-O-subst. Manp units (13%). Mild reductive beta-elimination of RMP-Sp gave alpha-l-Rhap-(1-->2)-alpha-l-Rhap-(1-->3)-alpha-l-Rhap-(1-->3)-alpha-d-Manp-(1-->2)-d-Man-ol, with Man-ol substituted at O-6 with beta-d-Galp units, a related pentasaccharide lacking beta-d-Galp units, and beta-d-Galp-(1-->6)-[alpha-d-Manp-(1-->2)]-d-Man-ol in a 16:3:1w/w ratio. Traces of Man-ol and Rha-ol were detected. ESI-MS showed HexHex-ol and Hex(3-6)Hex-ol components. Three rhamnosyl units were peeled off successively from the penta- and hexasaccharide by ESI-MS-MS. The carbohydrate epitopes of RMP-Sp differ from those of the glycoprotein of Pseudallescheria boydii, a related opportunistic pathogen.

Scedosporium apiospermum: changing clinical spectrum of a therapy-refractory opportunist*

Current knowledge on the opportunist Scedosporium apiospermum (teleomorph: Pseudallescheria boydii), generated over a period of more than 120 years, is reviewed. The natural environmental habitat of the fungus is unknown; nutrient-rich, brackish waters like river estuaria have been suggested. The fungus is strongly promoted by agricultural and particularly by industrial pollution.

A novel murine model of cerebral scedosporiosis: lack of efficacy of amphotericin B

OBJECTIVES

Cerebral scedosporiosis is a life-threatening infection that is difficult to treat. The aim of this work was to develop a murine model of cerebral infection by Scedosporium apiospermum using intracranial inoculation and to use this model to evaluate the efficacy of amphotericin B deoxycholate and liposomal amphotericin B.

METHODS

Mice were rendered neutropenic by intraperitoneal cyclophosphamide and intravenous (iv) 5-fluorouracil administration. Animals were infected with iv or intracranial inoculation of 1 x 10(4), 5 x 10(4) or 5 x 10(5) cfu of a clinical strain of S. apiospermum. Tissue burden reduction was determined in kidneys and brain 4 days after the infection. Efficacy of amphotericin B and liposomal amphotericin B (0.8 mg/kg/day intraperitoneally and 40 mg/kg/day iv, respectively) was evaluated in neutropenic mice infected iv or intracranially with 5 x 10(4) cfu. Survival was analysed with the log-rank test. Fungal burden values of different groups were compared using the Mann-Whitney U-test.

RESULTS

In our model, intracranial infection produced a higher fungal load in the brain and a lower fungal load in the kidney than iv inoculation. Survival of animals infected intracranially and treated with amphotericin B or liposomal amphotericin B (mean survival time = 8.3 and 9.2 days, respectively) was not different from the control group (P=0.58 and 0.85, respectively).

CONCLUSIONS

We have developed a murine model of cerebral scedosporiosis, which may be useful for studying various pathological aspects of this infection and evaluating new therapeutic approaches. Amphotericin B and liposomal amphotericin B were unable to resolve the infection.

Interferon-gamma and colony-stimulating factors as adjuvant therapy for refractory fungal infections in children

A human immunodeficiency virus-infected boy with Scedosporium apiospermum otomastoiditis and a girl with diabetes mellitus and Mucor sinusitis and orbital cellulitis had life-threatening disease progression despite antifungal treatment. Interferon-gamma and granulocyte-macrophage or granulocyte colony-stimulating factor were added, with good functional outcome in both children. Adjunctive therapy with interferon-gamma, granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor can be considered for refractory invasive fungal infections.

The significance of isolation of saprophytic molds from the lower respiratory tract in patients with cancer

BACKGROUND

Invasive infections caused by molds other than Aspergillus, Fusarium, and Zygomycetes have been reported sporadically in patients with leukemia and allogeneic bone marrow transplantation (BMT). However, the significance of lower respiratory tract cultures that are positive for these saprophytic molds in an unselected population of patients with cancer remains unclear.

METHODS

The authors evaluated the significance of respiratory specimens positive for saprophytic molds in patients with cancer using the criteria set by the European Organization for Research and Treatment of Cancer (EORTC)/Mycoses Study Group (MSG). They included the diagnostic category of indeterminate pulmonary invasive mold infection (IMI) for cases that met the criteria for probable IMI but had other pathogens concomitantly isolated from the respiratory tract.

RESULTS

Eighty-five cases with at least 1 positive culture were identified in 79 patients. Two cases were proven IMI, 29 were indeterminate IMI, 5 were possible IMI, and 49 were no IMI. All 38 cases from patients with solid tumors represented colonization compared with only 11 of the 47 cases (23%) from high-risk patients (P < 0.0001). The positive predictive value (PPV) of cultures was 0% in patients with solid tumors and ranged from 4.3% to 76.6%, depending on the analytic model used, in high-risk patients with leukemia and recipients of BMT. Cultures positive for Scedosporium spp. had a higher PPV (9.1-100%) than did cultures positive for non- Scedosporium spp. (2.8- 69.4%).

CONCLUSIONS

Adjustments of the EORTC/MSG criteria may be required for the diagnosis of invasive infections caused by saprophytic molds, especially non-Scedosporium spp., in patients with cancer.

Breakthrough Scedosporium apiospermum (Pseudallescheria boydii) brain abscess during therapy for invasive pulmonary aspergillosis following high-risk allogeneic hematopoietic stem cell transplantation. Scedosporiasis and recent advances in antifungal therapy

Systemic scedosporiasis due to the anamorph or asexual form Scedosporium apiospermum (Pseudallescheria boydii) has become an important cause of opportunistic mycosis, especially in patients undergoing high-risk hematopoietic stem cell transplantation. We report a case of rapidly progressive cerebellar hyalohyphomycosis due to Scedosporium apiospermum in an allogeneic marrow graft recipient receiving treatment for severe graft-versus-host disease. This fatal breakthrough intracranial abscess, due to amphotericin B-resistant (minimum inhibitory concentration > 16 micro g/ml) mold, developed during the course of systemic antifungal therapy given for multicentric pulmonary aspergillosis. Despite treatment with high-dose Abelcet (10 mg/kg daily), free amphotericin B was not detected in postmortem cerebellar tissue. A broad-spectrum triazole-based agent (voriconazole/UK-109, 496--Vfend), and a novel fungal cell wall inhibitor, an echinocandin/pneumocandin analog (caspofungin/MK-0991--Cancidas), which exhibit excellent in vitro activity against most clinical Pseudallescheria boydii-Scedosporium apiospermum isolates, have recently become available in the United States and may provide much needed treatment options for patients at risk.

Comparison of the virulence of Scedosporium prolificans strains from different origins in a murine model

Scedosporium prolificans is an emerging opportunist fungus that causes different types of infections in immunocompetent and immunosuppressed people. These infections show an irregular geographical distribution and, generally, disseminated systemic infections are noticed only in specific countries. This study used a murine model of disseminated infection by this fungus to assess if strains from different origins have different virulence. Two strains from each of four different sources (disseminated infection, localised infection, asymptomatic cystic fibrosis patients and the environment) were tested. Two strains of S. apiospermum of clinical origin were also included in the study; these were clearly less virulent than those of S. prolificans. The S. prolificans strains tested were classified in three groups according to their virulence. The groups with higher and lower virulence were represented by only one strain each, and the intermediate group contained six strains. No significant differences were found between the strains from different geographic areas or different forms of disease.

Scedosporium infection in immunocompromised patients: successful use of liposomal amphotericin B and itraconazole

BACKGROUND

Invasive fungal disease is a major cause of death in immunocompromised patients. The filamentous fungus Scedosporium consists of two species, S. prolificans and S. apiospermum, which can cause infections in immunocompromised patients that are often fatal. A significant feature of this pathogen is its broad resistance to many antifungal agents, including amphotericin B.

PROCEDURE AND RESULTS

Five cases of infection with Scedosporium spp. occurred in patients with haematologic malignancies over a 10-month period. Three patients with S. prolificans were severely immunosuppressed and neutropenic; two were in relapse and another was early post-matched unrelated bone marrow transplant. All three died despite treatment with various combinations of amphotericin B and itraconazole. Two patients who were less immunosuppressed and had a normal neutrophil count developed S. apiospermum infection. Both were successfully treated with liposomal amphotericin B and itraconazole.

CONCLUSIONS

Disseminated infection in immunocompromised hosts with Scedosporium spp. is often fatal. However, in patients with a lesser degree of immunocompromise and particularly in those infected with the less virulent S. apiospermum, intensive antifungal therapy with liposomal amphotericin B and itraconazole may be associated with complete eradication of infection. Med Pediatr Oncol 2001;37:122-125.

Emerging pathogens

The ever increasing numbers of immunosuppressed individuals has led to a significant increase in the incidence of opportunistic infections, particularly those caused by fungi. The epidemiology of infections caused by the common fungal pathogens such as Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus has been well documented. However, in addition to these, a number of species which have previously been unrecognized (e.g., C. dubliniensis) or have previously been assumed to be non-pathogenic (e.g., Saccharomyces cerevisiae, Scedosporium spp. and Fusarium spp.) have emerged as agents of human disease. Since these species have only been identified recently as human pathogens, their role in disease is poorly understood. In most cases, identification of these species is problematic and therefore their epidemiology has yet to be elucidated adequately. In addition, several of these species fail to respond to conventional antifungal therapies. In this article, we describe the emergence of two separate yeast species (C. dubliniensis and S. cerevisiae) and two separate groups of moulds (Scedosporium prolificans and Fusarium spp.), as human pathogens. It is apparent from what we already know, that much work has yet to be performed before we have a clear understanding of how these species cause disease and most importantly how they can be controlled.

Airborne outbreak of nosocomial Scedosporium prolificans infection

We describe six inpatients with acute non-lymphocytic leukaemia who developed invasive infection with Scedosporium prolificans resistant to amphotericin B, flucytosine, ketoconazole, fluconazole, and itraconazole. All six patients died. Phenotypic and genotypic assessment of samples from clinical material and ambient air from the isolation rooms where the patients were being treated showed that the epidemic was caused by a single strain. After implementation of aerial control measures, there were no further infections with this organism. We conclude that fatal multidrug-resistant S prolificans epidemics can be aerially transmitted and can be prevented with implementation of appropriate infection-control measures.