Novel taxa of thermally dimorphic systemic pathogens in the Ajellomycetaceae (Onygenales)

Abstract

Summary Recent discoveries of novel systemic fungal pathogens with thermally dimorphic yeast-like phases have challenged the current taxonomy of the Ajellomycetaceae, a family currently comprising the genera Blastomyces, Emmonsia, Emmonsiellopsis, Helicocarpus, Histoplasma, Lacazia and Paracoccidioides. Our morphological, phylogenetic and phylogenomic analyses demonstrated species relationships and their specific phenotypes, clarified generic boundaries and provided the first annotated genome assemblies to support the description of two new species. A new genus, Emergomyces, accommodates Emmonsia pasteuriana as type species, and the new species Emergomyces africanus, the etiological agent of case series of disseminated infections in South Africa. Both species produce small yeast cells that bud at a narrow base at 37 °C and lack adiaspores classically associated with the genus Emmonsia. Another novel dimorphic pathogen, producing broad-based budding cells at 37 °C and occurring outside North America, proved to belong to the genus Blastomyces, and is described as Blastomyces percursus.

In Vitro Antifungal Susceptibility of Yeast and Mold Phases of Isolates of Dimorphic Fungal Pathogen Emergomycesafricanus (Formerly Emmonsia sp.) from HIV-Infected South African Patients

“…The first case of E. pasteurianus was described in an Italian patient with AIDS (8). Thereafter, several reports followed from Spain, China, India, and more recently, a single case from South Africa (2,(9)(10)(11)(12). E. orientalis has been reported only from a single immunocompetent Chinese patient (7).…”

“…In addition, Emergomyces differs from classic Emmonsia species by producing budding yeasts in vivo rather than adiaspores (5,6). Currently, the genus Emergomyces includes at least three species: the type species, Emergomyces pasteurianus, which appears to have a cosmopolitan distribution; a rarer species, Emergomyces orientalis, reported from China; and Emergomyces africanus, a species endemic to southern Africa (2,7). The first case of E. pasteurianus was described in an Italian patient with AIDS (8).…”

“…E. orientalis has been reported only from a single immunocompetent Chinese patient (7). At least two other unnamed species exist within Emergomyces, including a strain isolated from lung tissue of a man with rheumatoid arthritis in Germany and two isolates from immunocompromised patients in Canada (2).…”

“…Patients with disseminated emmonsiosis often present with a syndrome of fever, widespread skin lesions of various morphologies, pneumonia, anemia, elevated liver enzymes, and weight loss (2,13,15). Misdiagnosis is common (15).…”

“…dress the polyphyletic nature of fungi previously included in the Emmonsia genus (2,3). Unlike Emmonsia parva and Emmonsia crescens, which cause adiaspiromycosis, fungi within the genus Emergomyces cause disseminated emmonsiosis (or emergomycosis), a multisystem disease with a high case fatality rate (4,5).…”