Posted on Jul 11, 2011, 6 a.m.
Exophiala species black yeast fungi show remarkable tolerance to heat, high salt concentrations, aggressive detergents, and to both acid and alkaline water.
Modern living comes with an increasing need for electrical household equipment such as dishwashers, washing machines and coffee machines. A characteristic of these appliances is a moist and hot environment. In the case of dishwashers, high temperatures between 60º to 80ºC are intermittently produced and aggressive detergents and high concentrations of salt are used in each washing cycle. P. Zalar, from the University of Ljubljana (Slovenia), and colleagues have discovered that a potentially pathogenic fungus has found a home living in such extreme conditions. The team sampled private homes from 101 cities on 6 continents: 62% of the dishwashers contained fungi on the rubber band in door, 56% of which accommodated the polyextremotolerant black yeasts Exophiala dermatitidis and E. phaeomuriformis. Both Exophiala species showed remarkable tolerance to heat, high salt concentrations, aggressive detergents, and to both acid and alkaline water. This is a combination of extreme properties not previously observed in fungi. Exophiala dermatitidis is rarely isolated from nature, but is frequently encountered as an agent of human disease, both in compromised and healthy people. It is also known to be involved in pulmonary colonization of patients with cystic fibrosis, and also occasionally causes fatal infections in healthy humans. The researchers warn that: “We conclude that high temperature, high moisture and alkaline pH values typically occurring in dishwashers can provide an alternative habitat for species also known to be pathogenic to humans.”
P. Zalar, M. Novak, G.S. de Hoog, N. Gunde-Cimerman. “Dishwashers – A man-made ecological niche accommodating human opportunistic fungal pathogens .” Fungal Biology, 7 May 2011.