Dog Owner Homes Are Bacteria-Ridden – And That’s Not Necessarily A Bad Thing

Peter Suciu for — Your Universe Online

Man´s best friend could be his immune system´s worst enemy, suggests a new report in the journal PLOS ONE. Or maybe not.

According to a recently published study from researchers at North Carolina State University and the University of Colorado, Boulder, people who live with a pet dog harbor more types of bacteria in their homes than those who do not — and that includes species of bacteria that are rarely found in dog-free households.

“We wanted to know what variables influence the microbial ecosystems in our homes, and the biggest difference we’ve found so far is whether you own a dog,” said co-author Rob Dunn, an associate professor of biology at NC State.

“We can tell whether you own a dog based on the bacteria we find on your television screen or pillow case,” Dunn said. “For example, there are bacteria normally found in soil that are 700 times more common in dog-owning households than in those without dogs.”

While a massive influx of bacteria may seem like a nightmare to the compulsive cleaners among us, some research suggests that it may actually hold benefits for canine lovers. For example, pregnant women who have a pet dog are less likely to have children with allergies. This phenomenon hasn´t been proven as a cause-and-effect relationship, but some researchers speculate that it may be due to the pregnant woman’s exposure to a wider range of microbes.

In the study, 40 volunteers sampled nine common surfaces in their home using sterile swabs: a television screen, kitchen counter, refrigerator, toilet seat, cutting board, pillow case, an exterior door handle, and the door frames on both interior and exterior doors. The team then used DNA sequencing techniques on the swabs to determine which microorganisms were present.

After finding over 7,700 types of bacteria in the homes, researchers grouped the sampled surfaces into three categories: surfaces we touch, food surfaces and places that gather dust. Each category tended to have its own specific set of bacteria. For example, refrigerators, kitchen counters and cutting boards all had similar food-related bacteria species, while doorknobs, pillow cases and toilet seats had microorganisms more closely related to human skin.

“We leave a microbial ‘fingerprint’ on everything we touch,” Dunn explained. “Sometimes those microbes come from our skin, sometimes they’re oral bacteria and — as often as not — they’re human fecal bacteria.”

According to the authors´ conclusion, the different ℠habitat´ categories showed much more variation than different homes.

“This makes sense,” Dunn said. “Humans have been living in houses for thousands of years, which is sufficient time for organisms to adapt to living in particular parts of houses.”

“We know, for example, that there is a species that only lives in hot-water heaters,” he added. “We deposit these bacterial hitchhikers in different ways in different places, and they thrive or fail depending on their adaptations.”

The team is currently processing another 40 homes and preparing for a national survey of 1,300 homes across the United States.

“The larger sample size will help us better understand the range of variables that influence these microbial ecosystems,” Dunn said. “Does it matter if you have kids or live in an apartment? We expect the microbial populations of homes in deserts to be different from the populations of homes in Manhattan, but no one knows if that’s true. We want to find out.”