June 21, 2011

Dishwashers Could Harbor Harmful Fungus

Scientists have found that harmful fungal pathogens are enduring high temperatures, aggressive doses of detergents and rinsing salts, and both acid and alkaline types of water to take residency in dishwashers.

The scientists took samples of the fungi in 189 homes in 101 cities on six continents.

They said 56 percent of the dishwashers contained the black yeasts called Exophiala dermatitis along with its cousin fungus E. phaeomuriformis on the rubber seal on the appliance door.

The study said both species "are known to be able to cause systemic disease in humans and frequently colonize the lungs of patients with cystic fibrosis,"

According to the scientists, the fungi are "extremophile" organisms that are rarely found in nature.  This suggests they have found an evolutionary benefit by occupying a dishwasher, which provides a warm and moist home.

The study did not focus on whether the dishwasher fungi had been any threat to health.

It said "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," the paper, which was published in the latest edition of the journal Fungal Biology, said.

The scientists also found other microscopic species in the dishwashers, including:  Aspergillus, Candida, Magnusiomyces, Fusarium, Penicillium and Rhodotorula groups.

"The discovery of this widespread presence of extremophilic fungi in some of our common household appliances suggests that these organisms have embarked on an extraordinary evolutionary process that could pose a significant risk to human health in the future," the paper said.

The paper is published in the British Mycological Society journal, Fungal Biology, published by Elsevier


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