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Your kitchen sponge comes in contact with all sorts of unsanitary items in the sink, which is why it quickly becomes home to harmful bacteria. But can that sponge be properly cleaned or disinfected? Yes, it's possible—but it's only a temporary solution.
The Headline: Study Finds That Cleaning a Sponge Only Targets Its Worst Bacteria (New York Times)
The Story: A group of German researchers examined the bacteria present on 14 kitchen sponges, some that were regularly cleaned and others that weren't. The findings may be of interest to microbiologists, but not surprising for your typical sponge user. Here's the summary:
Kitchen sponges harbor a significant amount of bacteria
But none of them are likely to pose a deadly threat
Once you clean a sponge, it will inevitably get dirty again.
When you eliminate most or all of the bacteria in a contaminated area, the bacteria often return, though sometimes the mix of species may be slightly altered: more of one kind, fewer of another. This is what the researchers discovered in their study (though it's important to note they examined only 14 out of the countless kitchen sponges around the globe).
There's no reason to worry about these bacteria: even the ones deemed the 'worst' in the New York Times article are relatively harmless. None of them cause illnesses in healthy individuals. Even Moraxella osloensis, which was specifically mentioned, can coexist peacefully on your skin without any issues.
It’s quite normal to find skin bacteria on objects touched by your hands, and this certainly doesn't imply that cleaning is ineffective.
“Please note: we did not conduct our own tests on any sponge-cleaning techniques,” said Markus Egert, the senior author of the study, in an email. He doesn't have data yet on which cleaning method is superior, but he still believes in the importance of cleaning sponges and personally favors tossing them in the washing machine with detergent and bleach.
According to the Michigan State University extension, three other methods that are effective at killing bacteria include:
Microwave a wet sponge for one minute on high
Place it in the dishwasher on its longest and hottest cycle, including the drying phase
Soak it in diluted bleach for a minute
Since the bacterial composition in the sponge evolves over time, Egert suggests it may be wise to repurpose your kitchen sponge for other cleaning tasks (like using it in the bathroom) after a certain period. However, there is no data on exactly when a sponge becomes too old for kitchen use, so no firm guidelines exist.
The Takeaway: While clean sponges will eventually get dirty again, it's still worthwhile to clean them.
