High prevalence of the neurotrope Exophiala dermatitidis and related oligotrophic black yeasts in sauna facilities.

The black yeast Exophiala dermatitidis, an agent of fatal brain infections in East Asia, is common in European steam baths. The related fungi Sarcinomyces phaeomuriformis and Exophiala mesophila were isolated from locations in these complexes with lower ambient temperature and/or moisture. The latter two species had dry, rather than slimy, colonies and lower maximum growth temperatures (38 degrees C, 32 degrees C) than E. dermatitidis (42 degrees C). Exophiala dermatitidis produces abundant extracellular polysaccharide (EPS). The only E. dermatitidis strains lacking EPS were found outside the steam baths. Therefore it is likely that the extracellular polysaccharides commonly produced by E. dermatitidis are significant to survival under hot and moist conditions. Substrates sampled as controls, such as fruit surfaces and human faeces, yielded Exophiala dermatitidis at very low frequency.