A previous report published in Fungal Biology showcased how a group of researchers from institutions in Slovenia, the Netherlands and China took samples from the rubber seals inside 189 dishwashers from 18 countries and found that 62 percent of them tested positive for fungi.
The dishwasher would seem a nice place for fungi to dwell: it is moist and warm, and it has abundant organic matter to feed on in the form of food scraps. But dishwasher-dwelling fungi have to be of a hardy sort to handle the occasional burst of extreme heat as well as the alkalinity and salt content of dish detergents. In laboratory tests on the dishwasher-dwelling Exophiala dermatitidis and Exophiala phaeomuriformis, the researchers reported in Medical Mycology that the fungi are tolerant to a wide range of temperatures, pH levels and salt concentrations, a degree of so-called polyextremotolerance that had not been found before in fungi.
In that sense, the dishwasher fungi are something like domestic extremophiles, the life-forms that occupy seemingly inhospitable niches across the globe, from scorching hydrothermal vents in the deep ocean to frigid high deserts. Extremophiles are a popular subject for study because they demonstrate just how adaptable life is and offer hope that other planets, even those a bit different than Earth, could be inhabited.
If inhaled, these fungi can colonise the lungs and cause infections that can be difficult to treat. Breathing in spores from these fungi can cause persistent lung infections, particularly in people with compromised health.
"We were surprised to find some fungi that are extremely rare in nature but had really high numbers in dishwashers," says Nina Gunde-Cimerman, a professor of microbiology at the University of Ljubljana in Slovenia.
Fungi can survive almost anywhere and under extreme conditions, showing remarkable tolerance to cold, high concentrations of salt, harsh detergents, and high temperatures.
The Exophiala fungi, for instance, were mostly found in places with hard or medium-hard water--that is, water high in dissolved minerals such as calcium and magnesium. Beyond that, the researchers do not go into much detail about why dishwashers in certain countries seem to be more hospitable than others. For whatever reason, North America was especially fungi-friendly, with all six U.S. dishwashers sampled testing positive for fungi, along with six of seven Canadian dishwashers. Many European countries faired much better: only one of 10 Italian dishwashers was infested, whereas all five Spanish appliances got a clean bill of health.
Bacterial Growth Occurs After Stacking Partially Wet Dishes From Dishwashers
In one study, researchers identified bacteria on dishes (prior to washing) that had been used to serve meals to patients at a medical center. They then put half the plates through a full cycle of a dishwasher, stacking the plates after placing small amounts of water on each dish surface. The other 50 plates were machine-washed and then allowed to air dry for 24 hours.
Twenty-four hours after washing, the investigators found no apparent difference in bacterial growth between those stacked wet and those fully air-dried. However, after 48 hours a significantly higher amount of various bacteria were evident on the wet-stacked dishes.
Although the researchers did not determine exactly what types of bacteria had grown on the plates, they conclude that there is a risk of bacterial growth and food contamination if dishes are stacked wet after being run through an improperly working dishwasher or insufficiently dried after being hand washed.
Researchers warn that "the invasion of black yeasts into our homes represent a potential health risk." Their presence on plates or forks, for example, may spread infections even though none were reported in the sampled households. Only further study can determine if these dishwasher fungi can be dangerous to human health.
People who are taking antibiotics, those with poor immune systems, people with diabetes, and those with cystic fibrosis are particularly at risk of lung and skin infections caused by the fungi.
There are, however, things that you can do to reduce the amount of fungi in your dishwasher.
Fungus is a minute organism that is single-celled and can include yeasts, molds and mushrooms. It thrives by soaking up organic matter and the result is its decomposition. One effective avenue to combat the side effects of fungus is by using certain types of vinegar that can kill the bacterial and fungal growth.
Baking soda and vinegar will help to kill mold, mildew, and fungi growing on the inside surfaces of your dishwasher. This cleaning regimen should be done once per month to prevent fungi from taking hold.
Start by removing all racks and washing them by hand in hot soapy water. Use a soapy sponge to wipe down the dishwasher's interior surfaces and around the rubber door seal. Let everything air dry thoroughly.
Combine a half cup of white vinegar with 2 cups of hot water in a spray bottle. Spray all surfaces thoroughly and scrub with an old toothbrush around the crevices and seal. Use a scrub brush for large surfaces.
Put the racks back into the dishwasher. Fill a small glass bowl with vinegar and place it on the top rack. Run the washer on the hottest setting. Sprinkle 1 cup of baking soda on the dishwasher floor and run the machine a second time on high heat.
Alternative To A Dishwasher - Green Cleaning
You can save a lot of money, destress and experience a physical activity if you just take a bit of time to wash your dishes after every meal. There are countless benefits:
- Less Physical Clutter. How often were dirty plates, bowls, and glassware left on your kitchen counter following a meal just waiting to be loaded in the dishwasher? Each time, physical clutter is left on your kitchen counter, table, and sink.
- Save Energy. Because most dishwashers use the same amount of energy and water regardless of how full they are, you're always consuming energy if you wash 10 plates or 20.
- Less Mental Clutter. An unfinished project clutters the mind...always. Even when we were not in the kitchen, the pending responsibility of needing to clean the dishes was always hanging over our evening events. And you are specifically reminded every time we walked into (or even past) your kitchen.
- Seamlessly Transition Between Activities. Once the mind clutter of dirty dishes has been removed, you are free to move from activity to activity, event to event, and room to room. There is no need to return to the past and finish the duties of your meal.
- Dishes are Always Clean. Ever need that one mixing bowl, pot, or cooking utensil, only to find out that it’s still dirty sitting in the dishwasher? Washing dishes after every meal means the dishes and cooking utensils are always clean and in their drawer.
- Dishes get Cleaner. Don't you always hate pulling a bowl or plate out of the dishwasher that didn’t quite get all the way clean. Clean manually and dishes are cleaned fully, everytime.
- It Takes Less Time. Washing dishes after every meal will take less time than loading/running/unloading the dishwasher. After most meals, it takes only 2-3 minutes to handwash each item. Cups are a snap. And most plates are a breeze to clean immediately following a meal.
- Great Example for Kids. Kids will see parents who finish what they start, and they aren’t afraid to put in a little effort, and leave a room cleaner than they found it. And those are life disciplines they may embrace every day of their lives as they get older.
- It Brings Personal Satisfaction. There is a level of satisfaction in life that accompanies working with our hands and accomplishing a task without the need for mechanical intervention. There is a simple satisfaction in reminding ourselves that we can still live joyfully without machines.
April McCarthy is a community journalist playing an active role reporting and analyzing world events to advance our health and eco-friendly initiatives.