KCBD Investigates: What bacteria is lurking on the lid of your soda can?

Published: Oct. 4, 2016 at 8:37 PM CDT|Updated: Oct. 6, 2016 at 11:06 PM CDT
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Bacteria found on the lids of cans
Bacteria found on the lids of cans
Bacteria found on the lids of cans
Bacteria found on the lids of cans

LUBBOCK, TX (KCBD) - Soda cans, iced coffee, flavored water, you can buy a variety of drinks that conveniently come in cans.

We know what those cans are carrying on the inside, but what is lurking on the lid?

We bought cans from vending machines, gas stations and grocery stores that came in all sorts of packaging. We even snagged a can from the vending machine in the KCBD break room.

We then labeled each can, specifying not only where we bought it, but how it was packaged.

Then we took those cans to Dr. Michael San Francisco at Texas Tech University. Dr. San Francisco is Dean of the Honors College and a professor in the Department of Biological Sciences.

"Ninety-nine percent of the microbes we encounter in the environment are generally innocuous," Dr. San Francisco said.

"We have a large amount of microbes in and on our bodies. Most of these microbes are good and they are playing a role in protecting us."

However, if someone's immune system is weakened, they could be sensitized to the microbes, like the ones we tested for on the lids of the cans.

It did not take long for a variety of microorganisms and fungi to grow.

"Here is a very prolific growing fungus and I don't know what it is, but I wouldn't open this plate either, because each of those tips has spores that will puff out and spread into the environment," Dr. San Francisco said.

As scary as some of the bacteria looked, Dr. San Francisco said he was happily surprised by what he did not find.

"I was expecting to see more bacteria related to the E-coli and salmonella types and I didn't see those at all, which is a good thing," Dr. San Francisco said.

However, he did find something else.

"The medium is originally reddish in color and it has a sugar in it and it has a dye. When the microorganism uses that sugar and makes an acid then it will turn the dye from red to yellow as you see here. Often times that is diagnostics of certain gram positive bacteria such as Staphylococcus aureus," Dr. San Francisco said.

Dr. San Francisco said he was impressed with what he did not find on the can from the KCBD vending machine.

"I would think that because of the human handling, the extra human handling, would have more microbes and a greater variety of microbes. I was surprised that we didn't see that."

However, he said he did find enough bacteria on the cans to advise someone with a weakened immune system to take extra precautions.

"If you just wipe it down with a paper towel, you are not going to do anything, you are just spreading it around. So, if you are going to wipe it down, you may want to use something with a mild alcohol," Dr. San Francisco said.

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