Phaeohyphomycoses, emerging opportunistic diseases in animals

Shared Physiological Traits of Exophiala Species in Cold-Blooded Vertebrates, as Opportunistic Black Yeasts

Several species of the genus Exophiala are found as opportunistic pathogens on humans, while others cause infections in cold-blooded waterborne vertebrates. Opportunism of these fungi thus is likely to be multifactorial. Ecological traits [thermotolerance and pH tolerance, laccase activity, assimilation of mineral oil, and decolorization of Remazol Brilliant Blue R (RBBR)] were studied in a set of 40 strains of mesophilic Exophiala species focused on the salmonis-clade mainly containing waterborne species. Thermophilic species and waterborne species outside the salmonis-clade were included for comparison. Strains were able to tolerate a wide range of pHs, although optimal growth was observed between pH 4.0 and 5.5. All strains tested were laccase positive. Strains were able to grow in the presence of the compounds (mineral oil and RBBR) with some differences in assimilation patterns between strains tested and also were capable of degrading the main chromophore of RBBR. The study revealed that distantly related mesophilic species behave similarly, and no particular trend in evolutionary adaptation was observed.

Molecular taxonomy of scopulariopsis-like fungi with description of new clinical and environmental species

The taxonomy of scopulariopsis-like fungi, comprising numerous human opportunistic species, has recently been reassessed with delineation of the genera Microascus, Pithoascus, Pseudoscopulariopsis, and Scopulariopsis, using morphological data and multilocus sequence analysis based on four loci (ITS, LSU, EF-1α, and TUB). In this study, the same genetic markers were used to investigate a set of clinical and environmental isolates, morphologically identified as Microascus and Scopulariopsis spp. The ingroups of the concatenated phylogenetic tree resolved 41 species clades, with isolates distributed in four main lineages corresponding to the genera Microascus, Pithoascus, Scopulariopsis, and newly established genus Fuscoannellis, typified by Scopulariopsis carbonaria. The new species Microascus chinensis, Microascus onychoides, Microascus pseudolongirostris, Pithoascus lunatus, and Scopulariopsis macurae were described. Microascus trigonosporus var. terreus and Scopulariopsis alboflavescens were found different from M. trigonosporus and Scopulariopsis brevicaulis, respectively. All the species identified in the study, except Fuscoannellis carbonaria and S. macurae, originated from clinical samples, suggesting their potential role in human disease. The use of a four marker combination was demonstrated an efficient and reliable approach to infer phylogenetic relationships among the scopulariopsis-like fungi. Yet, the only genetic marker able to discriminate all species was EF-1α, therefore proposed as a secondary barcode for the identification of these fungi.

Isavuconazole, a broad-spectrum triazole for the treatment of systemic fungal diseases

The prodrug isavuconazonium sulfate (BAL8557) is an extended-spectrum water-soluble triazole, developed for the treatment of severe invasive and life-threatening fungal diseases. Its active moiety, BAL4815, is a potent inhibitor of ergosterol biosynthesis, resulting in the disruption of fungal membrane structure and function. The active compound shows broad-spectrum of activity and potency against all major opportunistic fungi, such as Aspergillus spp., Candida spp., Cryptococcus spp., Mucorales, Black yeasts and their filamentous relatives and the true pathogenic fungi, including Histoplasma capsulatum and Blastomyces dermatitidis. It is currently in Phase III clinical development for treatment of aspergillosis, candidiasis and mucormycosis, as well as other rare fungi infections. We reviewed the pharmacokinetic and pharmacodynamic characteristics of isavuconazole, and its microbiological and clinical investigation progress in advanced stages of development.

Cladosporium Species Recovered from Clinical Samples in the United States

Cladosporium species are ubiquitous, saprobic, dematiaceous fungi, only infrequently associated with human and animal opportunistic infections. We have studied a large set of Cladosporium isolates recovered from clinical samples in the United States to ascertain the predominant species there in light of recent taxonomic changes in this genus and to determine whether some could possibly be rare potential pathogens. A total of 92 isolates were identified using phenotypic and molecular methods, which included sequence analysis of the internal transcribed spacer (ITS) region and a fragment of the large subunit (LSU) of the nuclear ribosomal DNA (rDNA), as well as fragments of the translation elongation factor 1 alpha (EF-1α) and actin (Act) genes. The most frequent species was Cladosporium halotolerans (14.8%), followed by C. tenuissimum (10.2%), C. subuliforme (5.7%), and C. pseudocladosporioides (4.5%). However, 39.8% of the isolates did not correspond to any known species and were deemed to comprise at least 17 new lineages for Cladosporium. The most frequent anatomic site of isolation was the respiratory tract (54.5%), followed by superficial (28.4%) and deep tissues and fluids (14.7%). Species of the two recently described cladosporiumlike genera Toxicocladosporium and Penidiella are reported for the first time from clinical samples. In vitro susceptibility testing of 92 isolates against nine antifungal drugs showed a variety of results but high activity overall for the azoles, echinocandins, and terbinafine.

Fonsecaea pugnacius, a Novel Agent of Disseminated Chromoblastomycosis

We report a fatal case of a chromoblastomycosis-like infection caused by a novel species of Fonsecaea in a 52-year-old immunocompetent Caucasian male from an area of chromoblastomycosis endemicity in Brazil. The patient had a 30-year history of slowly evolving, verrucous lesions on the right upper arm which gradually affected the entire arm, the left hemifacial area, and the nose. Subsequent dissemination to the brain was observed, which led to death of the patient. The internal transcribed spacer (ITS) and partial large subunit (LSU), BT2, and CDC42 genes of the isolates recovered from skin and brain were sequenced, confirming the novelty of the species. The species is clinically unique in causing brain abscesses secondary to chromoblastomycosis lesions despite the apparent intact immunity of the patient. Histopathologic appearances were very different, showing muriform cells in skin and hyphae in brain.

Black yeasts and their filamentous relatives: principles of pathogenesis and host defense

Among the melanized fungi, the so-called "black yeasts" and their filamentous relatives are particularly significant as agents of severe phaeohyphomycosis, chromoblastomycosis, and mycetoma in humans and animals. The pathogenicity and virulence of these fungi may differ significantly between closely related species. The factors which probably are of significance for pathogenicity include the presence of melanin and carotene, formation of thick cell walls and meristematic growth, presence of yeast-like phases, thermo- and perhaps also osmotolerance, adhesion, hydrophobicity, assimilation of aromatic hydrocarbons, and production of siderophores. Host defense has been shown to rely mainly on the ingestion and elimination of fungal cells by cells of the innate immune system, especially neutrophils and macrophages. However, there is increasing evidence supporting a role of T-cell-mediated immune responses, with increased interleukin-10 (IL-10) and low levels of gamma interferon (IFN-γ) being deleterious during the infection. There are no standardized therapies for treatment. It is therefore important to obtain in vitro susceptibilities of individual patients' fungal isolates in order to provide useful information for selection of appropriate treatment protocols. This article discusses the pathogenesis and host defense factors for these fungi and their severity, chronicity, and subsequent impact on treatment and prevention of diseases in human or animal hosts.

Bipolaris hawaiiensis as an emerging cause of cutaneous phaeohyphomycosis in an Antillean manatee Trichechus manatus manatus

Phaeohyphomycoses are emerging and opportunistic diseases caused by dematiaceous fungi that infect many animal species. This paper describes a case of cutaneous phaeohyphomycosis in an Antillean manatee Trichechus manatus manatus caused by Bipolaris hawaiiensis. Blackish skin lesions were observed in an Antillean manatee calf held captive in Brazil. Direct examination of skin scraping from the affected areas revealed the presence of dematious hyphae. Culture of skin fragments led to the isolation and subsequent identification of B. hawaiiensis as the etiologic agent. Treatment with itraconazole for 14 d was effective. Infections by Bipolaris spp. are rare in animals, and this is the first report of B. hawaiiensis in veterinary medicine.

Phaeohyphomycosis caused by Exophiala spinifera: an increasing disease in young females in mainland China? Two case reports and review of five cases reported from mainland China

No more than 30 cases of phaeohyphomycosis caused by Exophiala spinifera have been reported up to now in English and Chinese literature over the past half century. Here, we reported two cases of phaeohyphomycosis caused by E. spinifera and reviewed all the five cases reported from mainland China. These two involved were both young female, one patient experiencing recurrence during pregnancy and the other developing multiple-site infections without apparent immunodeficiency. The aetiological agents were both identified as E. spinifera by molecular analysis. Oral itraconazole was proved effective enough for the first patient, while the combination of itraconazole and terbinafine was needed for the second patient. It seems that infections due to E. spiniferais increasing in China mainland nowadays, usually involving young female.

Cerebral and Ocular Ochroconiasis in 2 Elegant Crested Tinamou (Eudromia elegans) Chicks

Two elegant crested tinamou chicks (Eudromia elegans), aged 27 and 50 days, respectively, died following acute onset of weakness and neurologic disease. Microscopically, the cerebral hemispheres of both chicks and the optic lobes of 1 chick contained multifocal granulomatous and heterophilic inflammation and necrosis with intralesional pigmented, thin-walled, fungal hyphae. In 1 chick, hyphae extended along the optic nerve into the globe and were associated with severe granulomatous and heterophilic inflammation of the choroid, retina, pecten, and vitreous. In both chicks, polymerase chain reaction amplification of the fungal 28S large subunit ribosomal RNA was positive with 99% sequence identity to Ochroconis gallopava. While a well-characterized fungal infection of domestic poultry, ochroconiasis has rarely been reported in exotic avian species, and this is the first histologic characterization of ocular ochroconiasis in any avian species.

New disease records for hatchery-reared sturgeon. II. Phaeohyphomycosis due to Veronaea botryosa

A series of fungal cases in hatchery-reared juvenile and young adult Siberian sturgeon Acipenser baerii and white sturgeon A. transmontanus occurred at production facilities in Florida and California, USA, respectively. Affected fish exhibited abnormal orientation and/or buoyancy, emaciation, coelomic distension, exophthalmos, cutaneous erythema, and ulcerative skin and eye lesions. Necropsies revealed haemorrhage throughout the coelom, serosanguinous coelomic effusion and organomegaly with nodular or cystic lesions in multiple organs. Fungal hyphae were observed in 27 fish (24 A. baerii and 3 A. transmontanus) via microscopic examination of tissue wet mounts and on slides prepared from colonies grown on culture media. Histopathological examination of these infected tissues revealed extensive infiltration by melanised fungal hyphae that were recovered in culture. Phenotypic characteristics and sequencing of the fungal isolates with the use of the internal transcribed spacer region and 28S rRNA gene confirmed the aetiological agent as Veronaea botryosa. To our knowledge, this is the first documentation of V. botryosa infection in fish, although melanised fungi of the closely related genus Exophiala are well-known pathogens of freshwater and marine fishes.

Antifungal susceptibility patterns of opportunistic fungi in the genera Verruconis and Ochroconis

Species of Verruconis and species of Ochroconis are dematiaceous fungi generally found in the environment but having the ability to infect humans, dogs, cats, poultry, and fish. This study presents the antifungal susceptibility patterns of these fungi at the species level. Forty strains originating from clinical and environmental sources were phylogenetically identified at the species level by using sequences of the ribosomal DNA internal transcribed spacer (rDNA ITS). In vitro antifungal susceptibility testing was performed against eight antifungals, using the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method. The geometric mean MICs for amphotericin B (AMB), flucytosine (5FC), fluconazole (FLC), itraconazole (ITC), voriconazole (VRC), and posaconazole (POS) and minimum effective concentrations (MECs) for caspofungin (CAS) and anidulafungin (AFG) across the Ochroconis and Verruconis species were as follows, in increasing order. For Verruconis species, the values (μg/ml) were as follows: AFG, 0.04; POS, 0.25; ITC, 0.37; AMB, 0.50; CAS, 0.65; VRC, 0.96; 5FC, 10.45; and FLC, 47.25. For Ochroconis species, the values (μg/ml) were as follows: AFG, 0.06; POS, 0.11; CAS, 0.67; VRC, 2.76; ITC, 3.94; AMB, 5.68; 5FC, 34.48; and FLC, 61.33. Antifungal susceptibility of Ochroconis and Verruconis was linked with phylogenetic distance and thermotolerance. Echinocandins and POS showed the greatest in vitro activity, providing possible treatment options for Ochroconis and Verruconis infections.