Black yeast-like fungi in skin and nail: it probably matters

Black yeast-like fungi are rarely reported from superficial infections. We noticed a consistent prevalence of these organisms as single isolations from mycological routine specimens. To investigate the prevalence of black yeast-like fungi in skin, hair and nail specimens and to discuss the probability of these species to be involved in disease. Slow-growing black yeast-like fungi in routine specimens were prospectively collected and identified. A questionnaire regarding patient information was sent to physicians regarding black yeast-like fungus positive patients. A total of 20 746 dermatological specimens were examined by culture. Black yeast-like fungi accounted for 2.2% (n = 108) of the positive cultures. Only 31.0% of the samples, culture positive for black yeast-like fungi were direct microscopy positive when compared with overall 68.8% of the culture positive specimens. The most prevalent species were Phialophora europaea (n = 29), Coniosporium epidermidis (n = 12), Ochroconis cf. humicola (n = 6) and Cladophialophora boppii (n = 4). These are not common saprobes and thus less likely to be coincidental colonizers. In 10/30 cases, discolouration of nail/skin had been noticed. A limited number of black yeast-like fungi were repeatedly isolated from routine specimens suggesting that they may play a role in superficial infections or as colonizers. Keywords: Black yeast; melanised fungi; mycology; nail; skin; superficia