Chaetomium-like fungi causing opportunistic infections in humans: a possible role for extremotolerance

Members of the family Chaetomiaceae are ubiquitous ascosporulating fungi commonly, which reside in soil enriched with manure or cellulosic materials. Their role as human pathogens is largely ignored. However, the ability of some species to grow at high temperature enables them to play an important role as opportunistic pathogens. The family contains several genera and species that have never been reported to cause human infection. Hereby, three new species are described; two belong to the genus Subramaniula and one represents a Chaetomium species. Subramaniula asteroides was isolated from various sources including eye and skin infections as well as from the natural environment, and S. obscura was isolated from a toe infection. Chaetomium anamorphosum was isolated from a kidney transplant patient suffering from fungal peritonitis. All species described were previously misidentified as Papulaspora spp. due to the formation of cellular clumps or bulbil-like structures, which are characteristic of Papulaspora. The isolates failed to form sexual fruit bodies and ascospores remained absent, which is an unusual feature for the generally ascosporulating genera Chaetomium and Subramaniula; minute conidia from phialides were sometimes observed.