Can Concerns: The germs you're drinking

HUNTSVILLE, AL (WAFF) - You might be drinking more than just soda when you take a sip out of that can.

Studies have shown that a variety of germs can grow on the surfaces of canned beverages, which explains why one instinct is to rinse the can before drinking out of it.

"If cans are left out and different things could run across it, there could be interesting things on it," said Nikki Mertz, a biology graduate student and PhD candidate at the University of Alabama, Huntsville.

A WAFF 48 investigation sought to determine what sort of microorganisms could potentially grow on these cans, and whether the germs will make the drinker sick.

A similar study at the Baylor University Medical Center in Dallas, Texas found traces of enterobacter cloacae, a strain of bacteria that lives in the digestive tracts of humans and animals.

Mertz, who teaches microbiology lab at UAH, often assigns similar tests for her students in order to identify unknown bacteria found on everyday surfaces -- from elevator buttons to staircase rails.

In this instance, Mertz tested three different soda cans. Two came from a vending machine -- once rinsed, and one not rinsed. She also swabbed the surface of a soda can purchased from a gas station convenience store.

"We're going to do a swab with the mouth of the cans that we'll be drinking from. I'll be putting it on a plate that should grow just about anything," Mertz said.

72 hours later, the results showed several types of bacteria were was present on the cans, but none are dangerous for most people's health, if consumed.

The cultures revealed two types of staphylococcus on the unrinsed vending machine can, which according to Mertz, are harmless.

"These are all bacteria that are really common in the environment, everywhere from soil, water, air, dust, to just the normal flora found on our skin," Mertz said.

One of the staph strains, Staphylococcus arlettae, even serves a good purpose, Mertz said.

"They do use it in the textile industry to help reduce the toxicity of the dyes," she said.

Cultures from the rinsed can produced one type of bacteria.

"The most likely candidate for ours is Alcaligenes faecalis, which has been found in all bodily fluids," Mertz said.

For the most part, this genus of bacteria is harmless but Mertz said it can cause infections for those with compromised immune systems.

The third soda can from the gas station showed no evidence of bacteria.

"That one was completely clean. I even let it grow for up to 72 hours just in case there was a really slow grower in there; nothing at all," Mertz said.

While evidence of bacteria were found on these cans, the tests show one cannot completely avoid all bacteria.

"If you're a healthy individual, you're coming into contact with this bacteria on a daily basis anyway, not just on soda cans but on everything else,"  Mertz said.

Mertz also tested the surface of the vending machine buttons and found similar types of bacteria, leading Mertz to believe the germs come from the can's surrounding environment and possibly from hands.

"As long as you wash your hands regularly throughout the day, you'll probably be fine," Mertz said.

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