We use them all the time to clean our dishes and wipe our counter tops but did you ever stop to think what happens to all of that dirt you clean off?
Even if you give the sponge a good squeeze, little pieces of food and dirt will stay inside the sponge, stuck in all the gaps. Combine that with the heat from the warm water you just rinsed it under and you've got the best recipe for a bacteria magnet.
Worse yet is that scientists believe these little household essentials are even more of a bacteria hub than they originally thought.
A recent study published in Scientific Reports looked at the microbiome - or community - of bacteria in 28 samples from 14 different kitchen sponges.
What they discovered surprised them. They found that half of the ten most frequently detected types of bacteria (Acinetobacter johnsonii, Acinetobacter pittii, Acinetobacter ursingii, Chryseobacterium hominis and Moraxella osloensis) were linked to pathogens - those that cause sickness.
They also found smaller levels of the type of bacteria groups that can cause infection of strep.
The used sponges were compared to unused sponges, which had more or less no bacteria in them.
'Our work demonstrated that kitchen sponges harbor a higher bacterial diversity than previously thought,' the researchers said.
Moreover, the study found that most of the bacteria tended to colonize the surface layers of the sponge, rather than deep down below the surface, and that they were 'actively growing.'
A lot of people like to boil their kitchen cloths and sponges out of a belief that this will kill the bacteria and make them good as new.
But the study contradicted this common domestic practice as it found that microwaving or boiling sponges could eliminate around 60 per cent of the bacteria but not completely kill them all. And worse than that, the researchers believe that the ones that survive the heat are the strongest, most resistant types of bacteria so they only become harder to kill.
To get around this problem, the scientists recommended replacing the sponges altogether instead of trying to boil out the bacteria.
As the bacteria colonies grow, they suggested the kitchen sponges should be replaced on a weekly basis.
They said: 'We believe that in view of the high bacterial load of kitchen sponges, the dominance of bacteria closely related to species that clearly can cause infections in humans warrants attention and underlines the need for appropriate hygiene measures.
'Kitchen sponges are likely to collect, incubate and spread bacteria from and back onto kitchen surfaces, from where they might eventually find their way into the human body, e.g. via the human hands or contaminated food. In addition, direct contact of a sponge with food and/or the human hands might transfer bacteria in and onto the human body, where they might cause infections, depending on their pathogenic potential and the environmental conditions.'
