Study: Many More Microbes Found in Homes With Dogs Than Without

New research from North Carolina State University and the University of Colorado shows that households with dogs are home to more types of bacteria - including those rarely found in households without dogs.

The study found an overall 7,726 different kinds of bacteria existing within three general of areas of the canine homes ---  places humans touch, places food touches and places that usually don't get touched, where dust collects, according to a report by Science Codex.

"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 Dr. Rob Dunn, an associate professor of biology at NC State and co-author of a paper describing the work.

"We can tell whether you own a dog based on the bacteria we find on your television screen or pillow case," he 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."

Researchers determined the types of bacteria found in refrigerators, on kitchen counters and on cutting boards tended to be similar, because they were mainly linked to food.

The bacteria found on doorknobs, pillow cases and toilet seats, meanwhile, were also similar, as they came from humans.

The study also found that each of the locations sampled maintain its own unique population of bacteria.

Research assistants in 40 homes sampled nine common types of surfaces to help researchers determine what kinds of bacteria lived there, and to what extent.

The nine surfaces --- including television screens, kitchen counters, refrigerators, toilet seats, cutting boards, pillow cases, exterior door handles, trim around interior doors and trim around exterior doors --- were wiped with sterile swabs, from which researchers collected DNA to study which organisms were living where.

"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. We deposit these bacterial hitchhikers in different ways in different places, and they thrive or fail depending on their adaptations."

Humans --- and their pets --- leave microbial fingerprints, or, paw prints, as the case may be, on everything they touch, Dunn said. "Sometimes those microbes come from our skin, sometimes they're oral bacteria and, as often as not," they're fecal bacteria.

The researches indicted the household microbial differences are important because they could help explain differences in individual health.

For example, it's been known for some time that women who live around dogs while pregnant are less likely to have children with allergies.

Although a direct causal link between dog habitats and a lack of allergies has still not been found, more than a few researchers have hypothesized that the greater childhood resilience is at least aided by the mothers' exposure to a wider variety of microbes introduced by their four-legged family members.

Researchers are currently processing samples from another 40 homes and are preparing to analyze samples from a survey of 1,300 homes across the United States, which sampled four sites in each home, representing the various habitat categories.