We all have our own germ fingerprint

This article was originally published in the San Francisco Chronicle on September 10, 2014.

It’s no secret that we carry germs and transmit them to the surfaces inside our homes and the people who occupy them with us. But when it comes to bacteria, a new study finds no two houses are alike, and the microbes say a lot about you and whom you live with.

Scientists from the U.S. Department of Energy and the University of Chicago followed seven households for six weeks, swabbing occupants’ hands, feet and noses, doorknobs, light switches, floors, countertops and other surfaces. They found that each person and pet in those homes carried a distinct blend of bacteria, or a “microbial fingerprint,” and they left traces of their fingerprints throughout their homes.

Occupants also shared their bacteria with one another. Not surprisingly, those with the most physical contact, like spouses or parents and young children, had the most bacteria in common, especially on their hands.

The study’s lead author, microbiologist Dr. Jack Gilbert, said this knowledge could be useful in forensic science. Given a bacteria sample from an unidentified home in the study “we could easily predict which family it came from,” he said in a statement.

During the study, three families moved, and their microbial fingerprints permeated the new houses in less than a day. The data suggests bacterial levels in a house will change if even one person stops living there.

“You could theoretically predict whether a person has lived in this location, and how recently, with very good accuracy,” Gilbert said.