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United States Department of Agriculture

Agricultural Research Service

Title: Molecular Genetic Variation in Emmonsia Crescens and E. Parva, Etiologica Agents of Adiaspiromycosis, and Their Phylogenetic Relationship to Blastomyces Dermatitidis and Other Systemic Fungal Pathogens

item Peterson, Stephen

Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 28, 1998
Publication Date: N/A

Interpretive Summary: The mold species Emmonsia parva and E. crescens are generally not human pathogens but have been found infecting patients suffering from AIDS or those with other conditions that weaken the immune system. These molds appear to be related to fungi that can cause death in humans, and we assessed the relationship of these molds to the human pathogens to see whether these are variants of the human pathogens or distinct species. We found that these molds are distinct species that lack fundamental abilities to cause serious disease in humans. The DNA sequence database will allow medical professionals to distinguish between potentially fatal and non-fatal mold infections with complete certainty.

Technical Abstract: Emmonsia crescens, agent of adiaspiromycosis, Blastomyces dermatitidis, agent of blastomycosis, and Histoplasma capsulatum, agent of histoplasmosis, are known to form meiotic (sexual) stages in the ascomycete genus Ajellomyces (Onygenaceae, Onygenales), but no sexual stage is known for E. parva, the type species of Emmonsia. To determine whether E. parva is a member of the Ajellomyces clade, sequences from ITS and large subunit ribosomal DNA from 33 isolates preliminarily identified as E. parva and E. crescens, as well as isolates of B. dermatitidis, H. capsulatum, and Paracoccidioides brasiliensis, were phylogenetically analyzed. The analyses showed that B. dermatitidis and E. parva are sister species and distinct from Emmonsia crescens. Isolates of E. crescens formed into two groups that correlate with their continent of origin: boreal Eurasian isolates form one phylogenetic branch, and North American strains form a separate phylogenetic branch. Both branches include sexually compatible and incompatible strains. Most isolates of E. parva are placed into two closely related groups. Significant variability occurs among remaining Emmonsia-like isolates, including some from human sources, and isolates are placed on several phylogenetic branches. Paracoccidioides brasiliensis and H. capsulatum are ancestral to most Emmonsia isolates, and P. brasiliensis, which has no known teleomorph, falls within the Ajellomyces clade.

Last Modified: 4/22/2015
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