Scientists have found a possibly harmful fungus that grows in dishwashers, surviving high temperatures, aggressive doses of detergents and rinsing salts and both acid and alkaline types of water.
A black yeast called Exophiala dermatitidis was found with a cousin fungus, E. phaeomuriformis, in samples taken from dishwasters in 189 homes in 101 cities in six continents.
Fifty-six percent of the dishwashers contained the fungi on the rubber seal on the appliance door.
Both species "are known to be able to cause systemic disease in humans and frequently colonize the lungs of patients with cystic fibrosis," says the study.
The fungi are "extremophile" organisms that are rarely encountered in nature. This suggests they have found an evolutionary benefit by occupying a household niche, thriving on warmth and moisture.
The study appears in the latest edition of the journal Fungal Biology, published by the British Mycological Society.
The probe did not focus on whether the dishwasher fungi had been any threat to health.
It says, though, "further search is imperative" given the risk of genetic mingling in this unusual environment.
"The co-existence of different genotypes of the same species possibly enables genetic recombination, resulting into new genotypes with unknown pathogenic potential," says the paper.
Other microscopic species found in the dishwashers were members of the Aspergillus, Candida, Magnusiomyces, Fusarium, Penicillium and Rhodotorula groups.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies