The researchers analyzed the rubber seal on 24 dishwashers, according to the study published Jan. 12 in "Applied and Environmental Microbiology."
"Bacterial genera such as pseudomonas, escherichia and acinetobacter, known to include opportunistic pathogens, were represented in most samples," the researchers wrote.
"The most frequently encountered fungal genera in these samples belonged to candida, cryptococcus and rhodotorula, also known to include opportunistic pathogenic representatives."
The age of the dishwasher, how often the dishwasher is used, and the hardness of incoming tap water had "significant impact on bacterial and fungal composition," the researchers said.
Don't burn your dishwasher yet
Opportunistic pathogens are capable of causing disease only when a host's resistance is lowered, such as someone with a compromised immune system, a prior infection, or the elderly, according to the National Center for Biotechnology Information.
"The risk is probably in the realm of a shark attack," Erica Hartmann, an assistant professor at Northwestern University, told HealthDay.
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But while most people face little to no risk, those with conditions that weaken their immune systems may face a higher risk, HealthDay added.
And, as the study researchers noted, "Worldwide demand for household appliances, such as dishwashers and washing machines, is increasing, as well as the number of immune-compromised individuals."
Bacteria and fungi
Escherichia covers strains such as E. coli, which can be life-threatening, The Daily Mail reports. Pseudomonas can cause chest infections, and acinetobacter is linked to urinary tract, skin and inner heart lining infections, The Daily Mail said.
The fungus candida (which was found in 100 per cent of the dishwashers in the study) can cause thrush, according to the Public Health Agency of Canada. In very rare cases, those with a genetic defect to the immune system's response to thrush can experience chronic thrush infections that lead to death, the agency said.
Dishwashers are artificial extreme environments, study researcher Nina Gunde-Cimerman said in a press release. It's suspected that bacteria and fungus get into the dishwashers via food, tap water, people and pets, she told HealthDay.
To keep the microbes contained, don't open the dishwasher before it's cooled down, she said.
In October, Health Canada recalled 61,000 dishwashers due to a risk that they could catch fire.
(See? We told you that you didn't need to burn yours. It might just happen, anyway).