Pseudallescheria: an underdiagnosed fungus?

Recurrent Scedosporium apiospermum Cutaneous Infection in a Patient with Rheumatoid Arthritis: The Potent Role of IL-6 Signaling Pathway Blockade: A Case-Based Review

Rheumatoid arthritis (RA) patients deal with a higher risk of bacterial and fungal infections compared to the general population because of their dysregulated immune system as well as the immunosuppressive therapy they usually receive. Scedosporium spp. is a fungal pathogen responsible for cutaneous, lung, central nervous system, and eye infections, mostly in immunocompromised patients, leading to death in disseminated cases. We report the case of an 81-year-old woman with rheumatoid arthritis treated with steroids and an IL-6 inhibitor who was diagnosed with scedosporiosis of the upper limb. She was treated with voriconazole for one month, which was discontinued due to adverse events, and when scedosporiosis relapsed, she switched to itraconazole. We also reviewed the current literature on RA patients presenting with Scedosporium infections. Early and accurate diagnosis of scedosporiosis has therapeutic and prognostic implications, as traditionally this fungus is resistant to commonly used antifungals. Clinical alertness regarding uncommon infections, including fungal, in patients with autoimmune diseases on immunomodulatory agents is essential for effective treatment.

Scedosporium and Lomentospora Infections Are Infrequent, Difficult to Diagnose by Histology, and Highly Virulent

OBJECTIVE

To further characterize the histomorphology and clinicopathologic features of colonization and invasive disease by Scedosporium and Lomentospora.

METHODS

We conducted a 20-year retrospective study. Patients with at least 1 histopathology specimen and concurrent culture were included. Clinical features, histopathology, microbiology, and outcomes were analyzed.

RESULTS

Eighteen patients were identified, and all were immunocompromised. Eight patients had colonization, while 10 had invasive disease (pneumonia [n = 3], skin and soft-tissue infections [n = 3], disseminated disease [n = 4]). Scedosporium apiospermum was identified in 15 patients, Lomentospora prolificans in 2 patients, and Scedosporium ellipsoideum in 1 patient. Fungal elements were identified histologically in 11 patients. Granulomatous, suppurative, and necrotizing inflammation with irregular branching hyphae and characteristic microconidia were observed in 9 cases; conidiogenous cells were identified in 4 cases. Seven patients died of invasive disease despite therapy, and 3 recovered after treatment. No deaths were observed in patients with colonization.

CONCLUSIONS

Scedosporium and Lomentospora are rare, virulent opportunistic fungal pathogens. Fungal morphology may overlap with other hyaline molds, but identification of obovoid conidia should allow a diagnosis of non-Aspergillus hyalohyphomycosis and consideration of Scedosporium and Lomentospora. Histopathologic correlation with culture and polymerase chain reaction is critical for diagnosis and treatment.

Localized cutaneous infection caused by Scedosporium apiospermum: Report of a case diagnosed on cytology

Scedosporium apiospermum (also known as Pseudallescheria boydii) is a ubiquitous filamentous fungus. This fungus is known as a cause of mycetoma, which may occur in a normal immune host following trauma and nonmycetoma-localized skin infections without grain production which are much rarer. However, in an immunocompromised host, S. apiospermum may cause a life-threatening infection. We describe a case of S. apiospermum infection of the left middle finger in an immunocompetent patient, which was diagnosed on cytology and later confirmed on culture.

Management of pulmonary Scedosporium apiospermum infection by thoracoscopic surgery in an immunocompetent woman

The Scedosporium apiospermum complex is a group of emerging opportunistic fungal pathogens that affect both immunocompromised and immunocompetent individuals, most commonly via lung infection. Although they are resistant to many antifungal agents, this group of pathogens has a favorable susceptibility profile to azoles, especially voriconazole. Here, we describe the management of S. apiospermum infection in an otherwise healthy 44-year-old woman. She had exhibited intermittent hemoptysis for 2 years before admission to our hospital. Computed tomography revealed a thin-walled and well-circumscribed cavitary lesion in the left upper lobe; the lesion was filled with consolidative opacities. Fungal culture of bronchoalveolar lavage fluid specimens revealed grayish-white mold; lactophenol cotton blue staining revealed acute angle branched septate hyaline cylindrical hyphae, characteristic of S. apiospermum. Despite voriconazole 200 mg twice daily for 8 weeks, the patient showed no improvement; thus, her left upper lobe was removed via thoracoscopic surgery. Her symptoms immediately improved and chest radiography after surgical resection showed no evidence of radiological progression or reoccurrence. This report demonstrates that S. apiospermum lung infection may not respond well to voriconazole alone in immunocompetent hosts; thus, surgery could be curative for these patients.

Canine rhinitis caused by an uncommonly-diagnosed fungus, Scedosporium apiospermum

A Golden Retriever cross was presented with a four week history of violent sneezing and licking at the nasal planum. Nasal mycosis was diagnosed and Aspergillus sp. presumed the causative agent, until culture, PCR and DNA sequencing showed that Scedosporium apiospermum, an uncommonly diagnosed, yet emerging, fungal pathogen, was the agent responsible. Debridement of the fungal plaques and systemic itraconazole therapy resulted in complete resolution of clinical disease. We discuss the current literature on S. apiospermum, review its clinical significance and question the validity of its ‘complex’ taxonomy.

ESCMID and ECMM joint guidelines on diagnosis and management of hyalohyphomycosis: Fusarium spp., Scedosporium spp. and others

Mycoses summarized in the hyalohyphomycosis group are heterogeneous, defined by the presence of hyaline (non-dematiaceous) hyphae. The number of organisms implicated in hyalohyphomycosis is increasing and the most clinically important species belong to the genera Fusarium, Scedosporium, Acremonium, Scopulariopsis, Purpureocillium and Paecilomyces. Severely immunocompromised patients are particularly vulnerable to infection, and clinical manifestations range from colonization to chronic localized lesions to acute invasive and/or disseminated diseases. Diagnosis usually requires isolation and identification of the infecting pathogen. A poor prognosis is associated with fusariosis and early therapy of localized disease is important to prevent progression to a more aggressive or disseminated infection. Therapy should include voriconazole and surgical debridement where possible or posaconazole as salvage treatment. Voriconazole represents the first-line treatment of infections due to members of the genus Scedosporium. For Acremonium spp., Scopulariopsis spp., Purpureocillium spp. and Paecilomyces spp. the optimal antifungal treatment has not been established. Management usually consists of surgery and antifungal treatment, depending on the clinical presentation.

Immunodetection of fungal and oomycete pathogens: established and emerging threats to human health, animal welfare and global food security

Filamentous fungi (moulds), yeast-like fungi, and oomycetes cause life-threatening infections of humans and animals and are a major constraint to global food security, constituting a significant economic burden to both agriculture and medicine. As well as causing localized or systemic infections, certain species are potent producers of allergens and toxins that exacerbate respiratory diseases or cause cancer and organ damage. We review the pathogenic and toxigenic organisms that are etiologic agents of both animal and plant diseases or that have recently emerged as serious pathogens of immunocompromised individuals. The use of hybridoma and phage display technologies and their success in generating monoclonal antibodies for the detection and control of fungal and oomycete pathogens are explored. Monoclonal antibodies hold enormous potential for the development of rapid and specific tests for the diagnosis of human mycoses, however, unlike plant pathology, their use in medical mycology remains to be fully exploited.

Diagnostic accuracy of histopathologic and cytopathologic examination of Aspergillus species

To assess the diagnostic accuracy of histopatho-logic and cytopathologic examination (HCE) of Aspergillus species (spp), we performed an 11-year retrospective review to correlate surgical/cytology cases with a diagnosis of Aspergillus spp with their concurrent fungal culture results. Diagnostic accuracy was defined as the percentage of cases with culture-proven Aspergillus spp divided by the number of cases diagnosed as Aspergillus spp on HCE that had growth on fungal culture. Ninety surgical/cytology cases with concurrent fungal culture were reviewed, 58 of which grew a fungal organism. Of these 58 cases, 45 grew an Aspergillus spp, whereas 13 grew an organism other than Aspergillus spp, including both common (Scedosporium, Fusarium, and Paecilomyces spp) and uncommon mimickers (Trichosporon loubieri), resulting in a diagnostic accuracy of 78%. The low diagnostic accuracy indicates that several fungal organisms can morphologically mimic Aspergillus spp and can only be distinguished by fungal culture and DNA sequencing.

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.

Scedosporium apiospermum infection after near-drowning

Scedosporium apiospermum and its teleomorph (sexual form) Pseudallescheria boydii are ubiquitous saprophytic fungi, which under specific conditions, such as near-drowning, may cause therapy-refractory and life-threatening infections. We reviewed 22 cases (eight children and 14 adults) of S. apiospermum infection after near-drowning reported in the literature including an additional paediatric case from our institution. Scedosporiosis after near-drowning was associated with high mortality (16/23, 70%) even in immunocompetent hosts. It affected mainly young (mean age 24 years) and immunocompetent (83% with no apparent immune defect) males (male to female ratio 2.5 : 1). Scedosporiosis after near-drowning was a slow progressive disease (mean survival time 87 days) involving virtually all body organs. However, central nervous system (CNS) dissemination predominated (21/23, 91%) presenting mainly as multiple brain abscesses (15/23, 65%). All 23 patients showed preceding clinical and/or radiological evidence of lung disease indicating the mode of invasion. Diagnosis was delayed (median time to diagnosis 28 days) and was made by culture (16/23, 69.5%) or culture and tissue examination (7/23, 30.5%). The majority of the patients (20/23, 87%) received antifungal treatment and underwent neurosurgery. While the optimal treatment remains undefined, the most recent reports indicated voriconazole as a potentially effective option. Better knowledge of scedosporiosis after near-drowning could lead to improved intervention and ultimately to more favourable outcome.

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.

Aspects of oxalosis associated with aspergillosis in pathology specimens

Oxalosis (calcium oxalate deposition) is associated with various conditions, including aspergillosis. Some Aspergillus species produce oxalic acid, which reacts with blood or tissue calcium to precipitate calcium oxalate. Calcium oxalate crystals exhibit various shapes and are strongly birefringent. These occur in cytological specimens, as well as in tissues of patients with Aspergillus infection. Aspergillus species are hyaline septate moulds, and they can be accurately recognized in pathology specimens only if conidial heads (fruiting heads) are present. When these structures are not observed, detection of associated oxalosis in a mould infection supports the pathological diagnosis of aspergillosis. The presence of oxalosis is helpful when microbiological identification or immunohistological techniques for fungi are not available. Calcium oxalate crystals can induce cellular injury by several mechanisms, and there is increasing evidence that oxalosis-induced tissue damage may occasionally lead to a poor clinical outcome. This review discusses the diagnostic value and the potential clinical significance of oxalosis associated with aspergillosis.

Fatal pulmonary scedosporiosis. Letal verlaufende pulmonale Scedosporiose

We report on a case of scedosporiosis in a 72-year-old German woman. Her disease started with a purulent ulceration of unknown course at her left foot. Soon after onset of oral antibacterial therapy she needed in-hospital treatment because of an acute pneumonia. The infection progressed despite the application of different antibiotics. Microscopic examination of tracheal fluid revealed fungal hyphae and therefore treatment with itraconazole was initiated. However, the patient developed renal failure, required mechanical ventilation and finally died in treatment-resistant septic shock. Post-mortem Scedosporium apiospermum was cultured from lung tissue taken during autopsy. This is the fourth case of human infection caused by Scedosporium species diagnosed in our laboratory during the last 4 years.