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Nasty germs may be lurking in your coffee maker

Germs love to lurk in coffee machines
Is there bacteria in your coffee maker? 02:31

CHICAGO --So what's really brewing in that cup of coffee you make every day?

It turns out germs love to lurk.

Ten Chicago area families let CBS 2 swab their one-cup coffee makers. Then CBS 2 reporter Mary Kay Kleist took the samples to Loyola University, where experts tested them for germs. Microbiologist Roman Golash tested the cup containing coffee grounds, underneath where the coffee comes out and the water reservoir. He found bacteria including gram-positive strains like staphylococcus, streptococcus and bacillus cereus. He also discovered enteric bacteria, or bacteria of the intestines, like e-coli.

"I think the high amounts of fecal material or the enteric organisms I would probably be concerned about," Golash said.

Five of the machines sampled had bacteria either on the machine, in the water or in both places. Test results found bacteria in just the water samples of three other machines and no bacteria at all in the samples taken from two of the machines.

Bacteria found in a coffee machine WBBM

Stephanie Mathews' machine had 100,000 colony-forming units of bacteria in the water reservoir -- the highest number of bacteria in all the samples. "That's gross," Mathews said.

Another resident, Tess Kearns, had bacteria in the water reservoir and in the coffee outlet area. "I definitely need to clean that more often," Kearns said. "I'm very skeeved out right now."

These germs could cause gastrointestinal issues and stomach upset in people, especially if they have compromised immune systems.

"Any organism, given the right situation to the right person, can cause a problem," Golash said.

He recommends that you wash your hands before using the machine and flush the system with vinegar to clean it regularly. It is also important to use filtered water, change the water after each use, and let the pieces completely dry after cleaning them.

"You know I'm not a germaphobe, but it is important to know what you're being exposed to," Kearns said.

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