How dirty is your cellphone?

Many of us slide our cellphones in our back pockets, charge them on our nightstands, set them on top of toilets when using a public restroom and near sinks when washing our hands. Germs live everywhere, and it's impossible to get rid of the bacte...


Many of us slide our cellphones in our back pockets, charge them on our nightstands, set them on top of toilets when using a public restroom and near sinks when washing our hands.

Germs live everywhere, and it's impossible to get rid of the bacteria that lives in every crevice of the human body, said Cindy Ault, associate professor of biology and chemistry at the University of Jamestown. But lucky for us, most bacteria aren't harmful.

So, just how dirty is your cellphone? Ault's microbiology class set out to answer that question.

"People these days are on their phones like 24/7, and just to see what is growing on there is kinda cool I think," said Jacob Olson, sophomore microbiology student at UJ.

This lab was optional for students, and almost the entire class, 31 students, showed up to participate.


"The most interesting thing to me was how interested the students were in it, I knew they liked to culture things, they always look their happiest when you give them a swab," Ault said. "It's just fun to see what grows from different places."

Experimental Process

On Nov. 17, students used sterile swabs dipped in saline solution to swipe the exterior surface of their cellphones, collecting any bacteria that were on the surface. They then rolled the swabs onto three different testing plates that would serve as a growth medium for bacteria.The plates were incubated aerobically at 37°C for two days, prior to refrigeration, until examination took place Dec. 2.

The plates held samples of three separate agars. An agar is a gelatinous substance derived from red algae or seaweed that can be used to solidify microbiological media. Agar can also be used as a thickener in foods, and is commonly found in Asian foods, including soups and jellies.

The first of the plates was a blood-agar plate, which serves as a "nutritious medium," for several kinds of bacteria to grow, Ault said.

The second, a mannitol-salt agar, tested for staphylococcus aureus, a major pathogen, meaning it can lead to infections. The third was a macConkey agar, which screened for E. coli.

The lab wasn't set up to culture for viruses, Ault said.

In between placing samples on separate plates, students would sterilize their tools using an open flame.


Ault said washing hands can help decrease the number of microbes that are on our skin, but even surgeons washing with a surgical scrub can't get rid of all bacteria.

"I think people underestimate how many microbes are on something you use all the time," said Christopher Peterson, sophomore microbiology student at UJ.

Ault said any bacteria that are transferred from the swab to the plate will continuously multiply, and eventually form a mass of cells called a colony. Colonies are visible to the human eye, and form in a range of colors.

Results of experiment

The experiment showed results of bacterial growth from organisms that would be commonly found on inanimate objects or on the hands, Ault said.

Out of 28 student summaries and 84 total plates, 17 blood-agar plates showed bacterial growth, while nine showed at least two separate spots of bacterial growth.

Fifteen mannitol-salt agar plates showed bacterial growth and five plates indicated two spots of growth, while none of the colonies tested positive for staphylococcus aureus.

One macConkey agar plate showed bacterial growth, but tested negative for E.coli.


"I'm happy to report no coliforms (a bacterial indicator, in this case for E. coli ), and as I would expect these students are all really good about washing their hands," Ault said. "You do a classroom of kids, you might not find the same thing."

Twenty-two total plates showed growth from at least two different species of bacteria, and three plates showed bacterial growth from five to six different bacterial species.

The bacterial growth colonies ranged in colors from white to yellow, and some green.

"The organisms on here are mostly organisms that you would find on the hands, or just on any dry, environmental surface," Ault said.

Morgan Martin, sophomore nursing student at UJ, had some bacterial growth from her cellphone, but was surprised there wasn't more.

"I thought there would be more growth to be honest, I was expecting it to just be disgusting," Martin said. "It was a lot better than I thought it was going to be."

Ault said that she anticipated respiratory-type organisms to form, which didn't show up in results.

"I should have tested my phone, because I talk instead of text," Ault said. "But on the other hand the respiratory organisms are the ones that normally live in the mouth are going to need a moist environment to survive, where some of the skin organisms can survive on drier surfaces."

Professional outlooks

Jennifer Schmidt, field epidemiologist in Jamestown, wasn't surprised by the results. Ault and Schmidt said a cellphone is a fomite, or any inanimate object capable of carrying bacteria from one individual to another. Schmidt said she wouldn't consider a cellphone a high-risk item for carrying infectious bacteria, because a cellphone is someone's personal equipment, and whatever is on your cellphone is usually also on your hands, unless someone else borrows your cellphone, which then you are exposed to a new set of germs, Schmidt said.

Jill Baber, Epidemiologist for the North Dakota Department of Health, said there is a variety of diseases that can be transferred by touching contaminated objects, such as cellphones, laptops, desks and keyboards. Baber said the timeline that bacteria can remain infectious depends on the virus, ranging from a couple of minutes to a couple of hours.

Individuals who contract norovirus, the most common food-borne illness, will shed the virus for up to 72 hours, Baber said. For influenza, the virus can be spread 24 hours before symptoms appear, and for five days after.

"(Cellphones) are a great place to pick something up if you're not washing your hands very well," she said.

Cleaning a cellphone

Washing a cellphone occasionally with a damp cloth is a good method for cleaning, while some recommend washing a cellphone with an alcohol-based solution, Ault said.

Ault also said to avoid using harsh chemicals on a phone, and for those who are interested, PhoneSoap, a Utah based manufacturer, has created a device that will charge and clean your cellphone using ultraviolet rays. The device can fit phones up to the size of an iPhone 6S Plus.

It's recommended to turn the phone off before washing. Also available are electronic wipes from brands including Windex and Pledge.


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