A recent study by researchers at Duke University revealed that kitchen sponges with both large and small holes promote the greatest microbial growth. Biologist Lingchong You examined the complex environment of kitchen sponges and found that varying sizes of porous material encourage bacterial proliferation.
The findings confirm the hidden risks associated with everyday kitchen sponges. The tool we use to clean our plates and cups is full of microbial life. Sponges are warm, moist, and come into contact with food residues, creating the perfect environment for bacteria to thrive.
In 2017, microbiologist Dr. Markus Egert from the University of Furtwangen in Germany published data on the bacterial microbiome of used kitchen sponges after sequencing the genetic material found in them. He discovered 362 species of microorganisms in these sponges.
“Our work shows that kitchen sponges harbor a much greater diversity of bacteria than was previously thought,” said Massimiliano Cardinale from the Institute of Applied Microbiology at Justus Liebig University in Giessen.
Among the bacteria found was Moraxella osloensis, which can cause infections in people with weakened immune systems and is responsible for the bad smell in dirty clothes. The bacterium could explain the unpleasant aroma of used kitchen sponges that are used repeatedly.
Although the bacteria discovered in the sponges are not associated with food poisoning or serious diseases, there may be a risk of infection for people with compromised immune systems, such as the elderly or children.
“Kitchen sponges are a paradise for bacteria because they are warm, moist, and full of nutritious food crumbs,” said Egert. “For most healthy people, the bacteria in kitchen sponges are not harmful. They were bad bacteria for the elderly or children with weak immune systems.”
Experts recommend disinfection measures to mitigate these risks. After use, it is advisable to remove as much moisture as possible, squeeze out water, and remove food particles. Disinfecting sponges with boiling water or by microwaving them is recommended, and it is advisable to replace them every one to two weeks.
“Using the high-temperature wash function of a dishwasher is effective for disinfecting sponges,” and studies showed that this method can be more effective than soaking in bleach.
However, traditional cleaning methods may not effectively eliminate bacteria over time. “Special cleaning measures like heating in the microwave or rinsing with hot water and soap did not achieve the desired effect; while some bacteria die, more resistant strains thrive,” according to studies.
“Our hypothesis is that cleaning measures may lead to a kind of selection process, where the few survivors can grow in large numbers again,” said Egert. He added, “If you do this a few times, it may lead to a selection of bacteria that are better adapted to the cleaning.”
Some experts suggest that brushes may be a better alternative. “A brush is much better because it contains fewer bacteria and dries more easily. It's also easier to clean,” said Egert.
In a study by Solveig Langsrud, when researchers introduced Salmonella into kitchen sponges, the pathogen thrived, but it died when placed in brushes.
“That makes sense because, for microbes, you have individualists, [like] bacteria that like to grow on their own, and you have bacteria that need the company of others. Within a sponge, you have so many different structures or niches that all are happy,” explained Egert.
While the level of bacteria found in kitchen sponges can be similar to that found in human fecal samples, the real issue is whether these bacteria are harmful to health. Bacteria exist everywhere: on our skin, in the soil, and in the air around us, and not all of them are harmful; many perform vital functions.
“The vast majority of the bacteria in sponges do not cause disease; they will just cause a bad odor, making their use unpleasant over time,” said Jennifer Quinlan from the Department of Food Safety at Prairie View A&M University. However, she warns, “There is a possibility that if you use a sponge to clean raw meat or raw chicken, you may have some of those pathogenic bacteria there, and studies have found that pathogens can be isolated from kitchen sponges.”
Therefore, experts emphasize the importance of maintaining the overall hygiene of the kitchen, which includes managing sponges and overall kitchen cleanliness.
From a hygiene perspective, it is ideal to replace sponges once a week, as using an old sponge can spread germs to dishes, cutlery, and hands, increasing the risk of food contamination.
The article was written with the assistance of a news analysis system.