Each of us lives in a unique cloud of germs, and we carry it everywhere we go, a new study finds.
It settles into our homes and even hotel rooms, and a person’s particular germ fingerprint may be a better way to track them than real fingerprints or even DNA, the researchers report in the journal Science.
They sampled seven families, including 18 people, three dogs and a cat. Three of the families moved during the study, so the researchers tested two houses plus hotel rooms for each of them.
The volunteers swabbed their hands, noses and feet, as well as floors, counters and other surfaces in their homes.
The analysis confirmed what scientists have learned in recent years about the microbiome — the collection of bacteria, yeast and viruses that live in and on our bodies. Each person has a unique collection of these germs. What they also found was that everyone spreads this cloud around.
“We had a young couple that moved from a hotel into a new house,” Jack Gilbert, an environmental microbiologist at Argonne National Laboratories and the University of Chicago, told NBC News. “Their microbiomes overwhelmed the microbiome of the hotel room so their hotel room looked more like their new home, microbially speaking.” And it only took a day for it to happen.
This aura or cloud of germs defines who people are and who they spend time with.
“The microbiome is a combination of all your microbial interactions,” Gilbert said. Babies are born virtually sterile, but quickly acquire germs from their mothers.
“You acquire your mother’s microbiome and that kickstarts you into a progression that goes up to about the age of 2 years old,” Gilbert, who led the study team, said. “By the time you are 2, you have reached this stable unique fingerprint.”
The new study shows you carry this cloud of germs everywhere, leaving them in the places you hang out most, such as home. In turn, this affects your relatives and, especially, your children.
“The microbial diversity of the home likely affects immune defense and disease transmission among its residents, so that tracking how people microbially interact with the indoor environment may provide a ‘road map’ to defining the health in our homes,” the researchers wrote.
Since babies spend most of their time indoors, they are soaking up the cloud of microbes left by their parents, or whomever and whatever they live with.
Studies have shown that the bacteria living in and on people affect diseases from eczema to stomach ulcers, may affect weight gain and might help keep them healthy. Heavy use of antibiotics is linked to often deadly infections with Clostridium difficile, for instance, and doctors believe it’s because the drugs wipe out healthy bacteria that keep C. diff at bay.
The researchers tracked bacteria called Enterobacter, which can cause stomach upsets, from one person’s hands to the kitchen counter, and then to someone else’s hands. “This doesn’t mean that the countertop was definitely the mode of transmission between the two humans, but it’s certainly a smoking gun,” Gilbert said. “It’s also quite possible that we are routinely exposed to harmful bacteria — living on us and in our environment — but it only causes disease when our immune systems are otherwise disrupted.”
The same may happen with allergies. Earlier this week, Catherine Nagler and colleagues at the University of Chicago showed that in mice, having a certain family of bacteria living in the stomach protected them from peanut allergies.
The findings bring Gilbert back to the so-called hygiene hypothesis about allergies — that people who develop allergies may not have been exposed to enough germs when they were young. It might be that having a large diversity of germs living in and on you, rather than any one specific bacteria, is protective Gilbert says.
“They are essential for us to understand our health in the 21st century,” he said. Having pets affected the microbiome, and so did plants. It might be possible for police to use microbiomes to track people in a way they cannot use fingerprints or DNA.
“You could theoretically predict whether a person has lived in this location, and how recently, with very good accuracy,” Gilbert said.
And these germs likely explain why dogs can track people so well over fields and forest. “Bacteria living on your skin metabolize. They grow on your sweat and they release aromatic compounds from your sweat. Those aromatic compounds are released into the air,” Gilbert said.
“The dogs can smell your unique scent released by the bacteria unique to you. Interestingly, mosquitoes find you the same way. They detect the bacteria aromatic compounds released by your sweat.”
The findings may also help explain why some people’s houses smell funny — above and beyond the obvious smell of, say, litter boxes or cooking broccoli.
“The bacterial populations that do live in the house are going to be the ones that cause a lot of that smell,” Gilbert said.