DAVID GREENE, HOST:
For the first time, scientists have figured out just how many tiny critters are living inside your kitchen sponge. Now, don't fear. NPR's Michaeleen Doucleff says there is something you can do about this.
MICHAELEEN DOUCLEFF, BYLINE: Imagine for a moment if we could see the bacteria around us, that there were special goggles you could put on that make the bacteria light up like fireflies. If you put these goggles on and then look around the house, there would be one thing that would light up like gangbusters.
MARKUS EGERT: Your kitchen sponge.
DOUCLEFF: Your kitchen sponge. That's Markus Egert at Furtwangen University in Germany. He recently used DNA technology to find all the bacteria living in 14 used sponges. When he estimated how many were there, he was blown away.
EGERT: Locally, the density of bacteria reached up to 45 billion per square centimeter.
DOUCLEFF: Forty-five billion bacteria in each square centimeter. That sounds like a huge number.
EGERT: That's a very huge number. Actually, there's hardly any habitat on Earth where you'll find similar densities of bacteria.
DOUCLEFF: In fact, sponges can have just as high concentrations of bacteria as your toilet, which sounds really unappetizing. But remember that just because something has a lot of bacteria in it doesn't mean it's dangerous. There are just a handful of species that cause almost all foodborne illnesses, like E. coli and salmonella. So what matters is which bacteria are there. So did Egert find any of these pathogens in the sponges?
EGERT: No, we did not find pathogens. There might have been some pathogens, but they were - they were just very rare.
DOUCLEFF: Actually, this fits with a previous study. A few years ago, Jennifer Quinlan at Drexel University went into the kitchens of a hundred families in Philadelphia and tested their sponges specifically for foodborne pathogens.
JENNIFER QUINLAN: We were able to find them, but they were rare. One or 2 percent had them.
DOUCLEFF: So do you think that this is a real risk to families? Do you think there - I mean, is there any data showing that a person gets sick from their sponge?
QUINLAN: Unfortunately, you know, that's the big mystery of foodborne illness. Where do we actually get it, right? It's really hard to track back. So what we do is just try to minimize the risk.
DOUCLEFF: Quinlan says there are a few easy things you can do. First off, keep the sponge away from raw meat.
QUINLAN: I would never recommend using a sponge on raw meat juice, for instance. If you're dealing with raw juices from meat or poultry, you should be using paper that can be disposed of.
DOUCLEFF: Second, don't keep sponges around for too long. Replace them every one to two weeks.
QUINLAN: That's reasonable to me.
DOUCLEFF: Finally, clean the sponge every few days. The USDA recommends putting it in the dishwasher with a heated dry cycle, or wet the sponge and then put it in the microwave for one minute.
QUINLAN: It doesn't sterilize it. But remember, the ones we want to kill are the E. coli, the salmonella, and those tend to be pretty heat-labile. So if you're sufficiently heating it then you are likely to get rid of those pathogens.
DOUCLEFF: And at the end of the day, Quinlan says, there's no reason to be afraid of your sponge. It's really not dangerous, and you're much more likely to catch a bug from a sick person at home or work than you are from doing your dishes. Michaeleen Doucleff, NPR News.
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