Tuesday, September 17, 2013

Adding Microbial Friends to My Network - Part One

According to a recent survey, 91% of Americans own a cell phone. These phones accompany us everywhere. Cars, workplaces, malls, parks...even the bathroom. All of these places are teeming with microbial life, and our phones serve as a surface for microbial colonization. Surf the internet on the subway, take a couple photos at a pumpkin farm, or check Facebook on the toilet (...ew...), and you will likely acquire some microbial souvenirs on your phone.

Although most of these microbial hitchhikers won't cause you any harm, there are concerns about the spread of disease-causing or antibiotic-resistant bacteria on phones. For example, researchers in Scotland found 84% of hospital patients' phones were colonized by microbes, including pathogenic bacteria such as Staphylococcus aureus.

Most studies investigating microbial colonization of phones examine a single time point. But how does microbial colonization of phones proceed over time? I recently got a chance to find out! Two weeks ago, my cell phone of 6 years suffered a fatal fall (i.e., I dropped it). I dutifully reported to my local wireless store and left with a brand new smartphone. That night, I realized my old phone's misfortune was a golden opportunity for a longitudinal study of microbial colonization of mobile phones! 

With a little more foresight, I would have tromped into the store with sterile cotton swabs to sample my new phone straight out of the box. Alas, I didn't think of it until later. But I did sample my phone within 24 hours, so the results can serve as a good "baseline" for future comparisons.

The details
Awesome lab tech Lari and I used two kinds of agar plates: (1) lysogeny broth (LB) agar and (2) trypticase soy agar (TSA) with 5% sheep's blood. We used sterile cotton swabs soaked in phosphate-buffered saline to swab the front and back of the phone (in halves). We then spread the swabs over the agar and incubated the plates at 37 degrees Celsius (98.6 degrees Fahrenheit, which is internal body temperature).

The results
Here are the plates after about 36 hours of incubation.
LB agar - front of phone