Environmental siblings of black agents of human chromoblastomycosis

Abstract

Agents of human chromoblastomycosis, a skin disease almost exclusively caused by members of the order Chaetothyriales, are assumed to be traumatically inoculated into the skin with sharp environmental materials such as plant thorns or wooden splinters carrying the respective opportunist. In the supposition that such fungi should have their main habitat in the environment, we investigated the occurrence of black fungi in living areas of patients with chromoblastomycosis. In South America Fonsecaea agents are prevalent as agents of the disease, while also related Cladophialophora species, known from other types of skin infections, are known from the continent. Ninety environmental isolates were preliminarily selected as possible agents of chromoblastomycosis, based on morphology. Judging from ITS sequence data isolates were attributed to the genera Cladophialophora, Cyphellophora, Exophiala, Fonsecaea, Phialophora, and Veronaea. A total of 45 fungi morphologically identified as Fonsecaea or Cladophialophora isolated from debris and thorns of living prickly plants in Brazil were processed for taxonomic studies. Phylogenetic analysis revealed that the isolates indeed belonged to the Chaetothyriales, but only rarely an agent of chromoblastomycosis was concerned; only two strains of F. pedrosoi and one F. monophora were isolated from debris plants. The remaining isolates belonged to hitherto unknown molecular siblings of Fonsecaea. Two novel taxa are introduced.