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

Sarah A Ahmed,A Alastruey-Izquierdo,Deanna A Sutton,Anne Van Diepeningen,Ziauddin Khan,G Sybren De Hoog,Tarek A A Moussa,S Ahmad,Johannes Z Groenewald,Oliver Cornely,Pedro W Crous,M J Najafzadeh,A J Kindo,Axel Hamprecht,Omar A Almaghrabi,Xue-Wei Wang,S B J Menken,Maria J G T Vehreschild,Hassan S Al-Zahrani

doi:10.1007/s13225-015-0338-5

Abstract

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.

Highlights

Melanized fungi are important causes of human infection
Based on phenotypic features the isolates were identified as Papulaspora species because of the formation of clumps or bulbil-like structures (Vinod Mootha et al 2012)
With molecular and phylogenetic analysis of six loci, the strains were found to belong to three new species which are described in the present study

Summary

Introduction

Melanized fungi are important causes of human infection. About 70 genera representing hundreds of species have been implicated in human disease (de Hoog et al 2013a; Guppy et al 1998; Revankar and Sutton 2010; Revankar et al 2002). Members of Chaetothyriales exhibit pronounced virulence and cause deep and systemic infections in immunocompetent humans, e.g. chromoblastomycosis or brain infection (Badali et al 2009; Revankar and Sutton 2010). Members of Pleosporales are preponderantly found as degraders of plants debris or as mild opportunistic pathogens; human infections mostly comprise traumatic inoculation of contaminated materials (Revankar and Sutton 2010). The significance of Sordariales was underlined (Badali et al 2011; de Hoog et al 2013b), the Chaetomiaceae whose prevalence has been underestimated because of diagnostic problems

Methods

Results

Conclusion