Study Shows Bacteria Present in Kids' Lunch Bag

Updated: 05/07/2013 9:53 AM By: Hannah Anderson

You wouldn't serve food on dirty plates or cook with dirty utensils. But every day parents send their kids off to school with lunch, often times packed in re-usable lunch bags that are dirty.

KSTP teamed up with University of Minnesota scientists to find out how dirty these bags are. We tested two dozen of bags from two area schools, including Stephanie Combey's son's bag, Allen, who's in preschool. Combey was curious about what would be found.

That's where Dr. Christian Mohr with the U of M Department of Microbiology comes in. Mohr and several of his students swabbed the inside and out, focusing on areas where kids would likely touch them: the handle, sides, top and bottom. Mohr's team then brought the samples back to the lab and plated them out in petri dishes.

"We did have some bags with significantly high numbers of bacteria on them," Mohr said, "bags that had very few on the outside but were loaded with bacteria on the inside."

Mohr grew bacteria from every single bag. Some of what was identified was bacteria found in nature and not typically harmful to healthy people.

However, the bacteria most often isolated on the bags, was what's called enteric bacteria.

"Examples of enteric bacteria would be e-coli, enterobacter, and klebsiella," Mohr said. "What is common among all of these bacteria is they're all common flora of the human intestine."

Mohr's team did not identify e-coli specifically, but said enteric bacteria, found in large numbers, can be an indicator of fecal contamination. Of all the bags tested, roughly 30 percent showed high levels of this type of bacteria. Mohr said 10 percent of the bags should probably be replaced. This means 60 percent were fairly clean, including Stephanie Combey's son Allen's bag.

Mohr described it as having moderate levels of bacteria on the outside, but very few on the inside.

"I don't focus on the outside, because the lunch bag gets carried, dropped everywhere," Combey said. "So I don't focus on that as much as I do on the inside and trying to clean that out regularly. It makes sense that the bacteria would transfer and things like that."

Mohr's recommended people should wash both inside and out of the bag for prevention.