Forensic scientists could soon use hand germs to help identify criminals and victims, according to a study.
Researchers led by Noah Fierer of the University of Colorado at Boulder swabbed individual keys on three personal computer keyboards, extracted bacterial DNA from the swabs and compared the results with bacteria on the fingertips of the keyboards' users.
They also lifted germs from an unspecified number of other private and public computer keyboards that the three individuals did not use to see if there was a cross-over between the bacteria on an individual's hands and bacteria on keyboards that had never been touched by that individual.
The bacteria on each person's fingers were "personal" and gave a much closer match to the germs on the keyboard they used than to bacteria found on keyboards they had never touched, the researchers said.
The researchers also swabbed nine personal computer mice that had not been touched for at least 12 hours and took bacteria samples from the palms of their owners.
The bacteria on each mouse were "significantly more similar" to those found on the owner's hand than to bacteria taken from 270 other hands, which were on record from previous studies.
"Each one of us leaves a unique trail of bugs behind as we travel through our daily lives," said Fierer, a professor at the University of Colorado's ecology and evolutionary biology department, adding that hand bugs could "become a valuable new item in the toolbox of forensic scientists".
Hand germs are abundant, can be lifted from small areas and are remarkably hardy. The re-searchers found that colonies of hand bacteria remain essentially unchanged after two weeks at room temperature, and recovered within hours of handwashing.
Fingerprints, however, can be smudged or impossible to obtain, such as on fabric.
And unless there is blood, tissue, semen or saliva on an object, it is often difficult to obtain enough human DNA for forensic identification, said the study published in the Proceedings of the National Academy of Sciences.
"Given the abundance of bacterial cells on the skin surface... it may be easier to recover bacterial DNA than human DNA from touched surfaces although additional studies are needed to confirm that this is actually true," the study said.