By Mary Kay Kleist

(CBS) — So what’s really brewing in that cup of coffee you make every day?

It turns out germs love to lurk.

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Ten Chicago area families let CBS 2 swab their one-cup coffee makers, and reporter Mary Kay Kleist took the samples to Loyola, where experts tested them for germs.

Your morning brew may contain more than caffeine. You could be getting a splash of bacteria along with your morning Joe.

Tested were these spots on the machines: the cup containing coffee grounds; underneath, where the coffee comes out; and the water reservoir.

Microbiologist Roman Golash at Loyola’s lab found bacteria including gram-positive strains like staphylococcus, streptococcus and bacillus cereus. He also discovered enterics, like e-coli.

The latter type of bacteria “I would probably be concerned about,” Golash says.

Naperville mom Claire Evans was shocked to hear her machine was heavy in levels of enteric organisms, meaning bacteria from the intestinal tract.

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

“That’s gross,” says Stephanie Mathews, whose machine had bacillus where the coffee pod goes.

Her machine also had the highest number of bacteria in the water reservoir: 100,000 colony forming units.

Tess Kearns also had bacteria in the water reservoir and in the coffee outlet area.

“I definitely need to clean that more often. I’m very skeeved out right now. Yikes,” Kearns says.

These germs could cause gastro-intestinal issues and stomach upsets in people, especially if they have compromised immune systems.

“Any organism, given the right situation to the right person, can cause a problem,” Golash says.

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He recommends that you wash your hands before using the machine and to flush the system with vinegar regularly. Use filtered water. Change the water after each use. Let the pieces completely dry after cleaning them.

The good news: These one-cup machines heat the water to about 192 degrees. So, if your machine is working properly, the intense heat will kill some of the bacteria.

Below are statements from manufacturers.



As with any kitchen appliance, we recommend regular cleaning of our machines. FLAVIA® brewers are designed to be quick and easy to clean. Drinks are dispensed directly into the cup, so there is no dispensing funnel to clean, and simply wiping down the machine on a regular basis with an antibacterial wipe will keep the machine and the drink in your cup clean.



Keurig is committed to creating brewers and packs in a way that brews the perfect cup of coffee, tea and other beverages while maintaining the highest safety standards.

Similar to other household appliances, Keurig brewers require basic maintenance in order to keep them clean and functioning properly.  For best results, we recommend descaling every 3-6 months using our descaling solution to keep the brewer free from scale or lime build up.  Vinegar may also be used.  We recommend consulting the brewer user manual or visiting our website at for video instructions or to purchase the descaling solution.  The water reservoir should be cleaned weekly by wiping it with a damp, soapy, lint-free, non-abrasive cloth and rinsing thoroughly. It should not be placed in the dishwasher.

If the brewer is not used for several days, we recommend running several cleansing brews through to remove any internal standing water.  If the brewer is stored for a length of time, we also suggest descaling prior to use.



Nespresso coffee machines are state of the art, and like any appliance, regular cleaning is essential. To make this process easy, Nespresso provides clear and detailed care and cleaning instructions with every machine and offers a kit to descale the machine to remove the effects of calcium build up. We encourage our consumers to remain diligent about cleaning to ensure the best coffee experience possible.

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Mary Kay Kleist