Over 50 billion bacteria! This kitchen tool that every household uses should really be replaced! (Recommendations included)

Where do you think your home is most likely to breed microorganisms? Is it the toilet that hasn't been cleaned for a long time, or the dirty clothes that haven't been washed for a week, or... the garbage that has been accumulated in the trash can for several days?

You probably won’t guess the real answer - the dishwashing sponge that you use almost every day may be the petri dish with the most microorganisms in your home .

The structure of a kitchen sponge

A dishwashing sponge that has been used in the kitchen for a long time may be home to hundreds of species of bacteria, and up to 54 billion bacteria may be hidden in every cubic centimeter.

A wide variety of bacteria are distributed almost everywhere in the sponge; the red in the picture represents bacterial colonies, and the cyan is the sponge's autofluorescence.

Many studies have shown that used kitchen sponges are the items with the highest number of bacteria in the entire home environment . In other words, if you are used to wiping the dishes and stoves with a sponge every time you wash the dishes, although it looks clean to the naked eye, in fact... you are likely to evenly spread bacteria on the surface of everything .

Note : This comparison scope is all inanimate objects in the home, and does not include living animals or humans themselves - after all, there are more than 100 trillion microorganisms on and in our bodies. In particular, the microorganisms in the intestines are an important part of our human body and play an important role.

So why does the seemingly harmless dishwashing sponge become a petri dish for microorganisms?

All this is thanks to its unique loose and porous structure - this structure not only helps us absorb and squeeze out water quickly when using it, but also can quickly foam when using detergent, creating excellent conditions for the survival of bacteria.

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This loose and porous structure is like building a "livable community" for bacteria . Bacteria of the same kind or those who prefer to live together can live in close areas; while those microorganisms that may have an inhibitory effect on each other or those who prefer to live alone can also live in relatively distant areas. In short, bacteria E and bacteria I can find their own suitable growth environment, live in peace with each other, and vigorously expand their own families.

The number of microorganisms in dishwashing sponges is not only huge, but also rich in variety. In just one dishwashing sponge, there are more than 118 genera and 362 species of bacteria.

This is because the dishwashing sponge is a loose and porous environment with its own space division effect , which can also prevent the extinction of one side caused by vicious competition among microbial populations . Everyone can find a small corner in the "huge" space to reproduce and thrive.

According to relevant research, environments with moderate spatial divisions, such as sponges, can grow the richest and most diverse bacterial communities. Compared with the pure and single agar culture dish in the laboratory, this multi-level distribution environment can be said to be a true "God-chosen culture dish".

Frequency of use and suitable environment for bacterial growth

In addition to the structure itself being very suitable for bacterial life, our frequent use of dishwashing sponges also allows the bacteria inside them to obtain a steady supply of "food and water" .

Even if we squeeze the dishwashing sponge again and again, some water will still remain inside. This slightly moist condition is perfect for bacteria to thrive . Every time we wash dishes, some food residue will enter the sponge when we wipe and scrub, becoming food for bacteria.

The "terrain" is suitable for growth, and the "survival resources" are quite abundant. It is no wonder that dishwashing sponges can become the base camp of kitchen bacteria. Once a dishwashing sponge is contaminated during use, microorganisms will multiply rapidly on its surface and inside. Wait, if an unused dishwashing sponge must be clean, then where does the contamination come from?

The answer may make you uncomfortable - you and the various foods you handle in your kitchen are the sources .

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We are exposed to a large number of microorganisms in the environment every day. They will attach to the surface of our skin and be transferred to various places we touch through contact. Especially in the kitchen environment, raw meat and fresh food that are constantly coming in and out will also introduce a lot of microorganisms . When we touch these items and then touch the dishwashing sponge, we will transfer the microorganisms to it.

For example, if you hold a raw egg in your hand, the salmonella on it may be transferred to your hands. When you pick up a kitchen sponge to wipe the countertop, the salmonella may penetrate into the sponge and establish its own large family in a small space inside.

In addition, when we wash various foods and utensils that are attached with microorganisms, the splashing water droplets will spread the microorganisms to the entire kitchen environment . The dishwashing sponge is usually placed next to the sink, and the splashing droplets will often fall on it, adding another resident to the bacterial community inside.

So, the place with the largest amount of microorganisms in our home is not the bathroom as you think, but... the kitchen.

When a kitchen sponge becomes a haven for microbes, it not only creates odors, but also transfers microbes to kitchen surfaces every time you use it. Fortunately, most of the bacteria in a dishwashing sponge are not pathogenic.

However, in the rich and huge microbial community, there are inevitably some guys who may do bad things, such as Salmonella, Escherichia coli, Pseudomonas aeruginosa and other harmful bacteria that may affect our health . If the dishwashing sponge is used improperly, these microorganisms may be transferred to the surface of food, and if there are pregnant women, the elderly, and children with cross-immunity in the family, foodborne diseases may occur.

Does it really help to clean your dish sponge regularly?

So can regular cleaning of dishwashing sponges effectively reduce the amount of microorganisms in them? The only thing we can say is that the effect is better than nothing.

Researchers once conducted a series of experiments on used kitchen sponges using common dishwashing detergents on the market that claim to have antibacterial effects. The results found that...if dishwashing detergent is applied to the surface of the dishwashing sponge regularly as recommended by the merchant, it cannot effectively reduce the amount of microorganisms in the dishwashing sponge .

The porous structure of the sponge not only provides a good environment for bacteria to attach and grow, but also becomes a natural "safe haven". In particular, a long-term dishwashing sponge will form a biofilm on its surface when regularly replenished with food residues, which inactivates the antibacterial components .

In addition, even if we can persist in using high-concentration detergent or alcohol for long-term soaking and disinfection, or use hot water or microwave ovens for high-temperature disinfection, it is difficult to reduce the amount of microorganisms in the dishwashing sponge to less than half. Once the dishwashing sponge returns to a normal environment and is used again, replenishing some water and food residues from time to time, the remaining microorganisms in it will quickly grow and develop again.

Do we have to coexist with these annoying and potentially dangerous microorganisms? Can our dishes and chopsticks not be "cleaned"?

The simplest and most effective method is to use a dishwasher directly, so that you no longer need to use dishwashing sponges in the kitchen, solving the problem from the root. The high-temperature washing and drying process of the dishwasher can effectively remove stains and sterilize efficiently.

But if conditions do not permit, or you just don't like using it, you can replace it with the following cleaning products that are relatively less prone to breeding bacteria.

① A dishwashing brush is a good choice. The structure of a dishwashing brush is simple, it is not easy for microorganisms to attach, and it is easier to spin dry and clean. In comparison, it is not so friendly to the reproduction of microorganisms. A comparative experiment found that the bacteria level observed in used brushes was lower than that in sponges, and Salmonella died faster in brushes.

②Disposable kitchen rags are also good. They are clean every time and thrown away after use, so there is no cross infection. Forget about traditional cotton rags. Although their structure is not as complex as dishwashing sponges, they are still good at breeding microorganisms.

③ There is also a wood pulp sponge that looks similar to a dishwashing sponge, but is relatively more complicated to use. This sponge can be dried very quickly after each use - it dries directly into a hard lump. Its large pores and quick-drying properties make it difficult for microorganisms to breed in it. Even if it is just laid flat, the wood pulp sponge will dry much faster than an ordinary sponge.

But no matter what, when it comes to reusable cleaning products, no matter how powerful they are, the most important thing is to change them frequently .

References

[1]Cardinale, M., Kaiser, D., Lueders, T., Schnell, S., & Egert, M. (2017). Microbiome analysis and confocal microscopy of used kitchen sponges reveal massive colonization by Acinetobacter, Moraxella and Chryseobacterium species. Scientific reports, 7(1), 5791.

[2]Flores, GE, Bates, ST, Caporaso, JG, Lauber, CL, Leff, JW, Knight, R., & Fierer, N. (2013). Diversity, distribution and sources of bacteria in residential kitchens. Environmental microbiology, 15(2), 588-596.

[3]Flores, GE, Bates, ST, Caporaso, JG, Lauber, CL, Leff, JW, Knight, R., & Fierer, N. (2013). Diversity, distribution and sources of bacteria in residential kitchens. Environmental microbiology, 15(2), 588-596.

[4]Ogunrinola, GA, Oyewale, JO, Oshamika, OO, & Olasehinde, GI (2020). The human microbiome and its impacts on health. International journal of microbiology, 2020.

[5]Zhu, B., Wang, X., & Li, L. (2010). Human gut microbiome: the second genome of human body. Protein & cell, 1(8), 718-725.

[6]Structure, function and diversity of the healthy human microbiome[J]. nature, 2012, 486(7402): 207-214.

[7]Wu, F., Ha, Y., Weiss, A., Wang, M., Letourneau, J., Wang, S., ... & You, L. (2022). Modulation of microbial community dynamics by spatial partitioning. Nature chemical biology, 18(4), 394-402.

[8]Kusumaningrum, HD, Van Putten, MM, Rombouts, FM, & Beumer, RR (2002). Effects of antibacterial dishwashing liquid on foodborne pathogens and competitive microorganisms in kitchen sponges. Journal of food protection, 65(1), 61-65.

[9]Møretrø, T., Ferreira, VB, Moen, B., Almli, VL, Teixeira, P., Kasbo, IM, & Langsrud, S. (2022). Bacterial levels and diversity in kitchen sponges and dishwashing brushes used by consumers. Journal of Applied Microbiology, 133(3), 1378-1391.

Planning and production

This article is a work of Science Popularization China-Starry Sky Project

Produced by: Science Popularization Department of China Association for Science and Technology

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.

Author: Science Popularization Team of Xinshi Science Popularization Studio

Review | Zhong Kai, Researcher at the National Food Safety Risk Assessment Center

Planning丨Yinuo

Editor: Yinuo