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Dirty dogs: Homes with pooches loaded with bacteria

A dog may not only fill a home with joy, it fills a home with a whole lot of bacteria, new research suggests.  But that doesn't mean you have to kick your pooch out of the bed.

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This adorable puppy is loaded with bacteria, but those germs may actually be beneficial.

Research from North Carolina State University published Wednesday in the journal PLoS ONE found homes with dogs have both a greater number of bacteria and more types of bacteria than homes without dogs. 

The findings were part of a larger study that analyzed the types of microbes living in 40 homes in the Raleigh-Durham area of N.C.  Participants swabbed nine areas of their homes and informed researchers about aspects that could influence bacterial life, such as whether there were dogs or cats and how many people lived in the home. 

“The project was a first step toward making an atlas of microbes found in the entire home and how they may affect our health and well-being” said Holly Menninger, a co-author and director of public science at NC State’s Your Wild Life program.

Of the places where household bacteria were found, pillowcases and television screens had the most detectable dog-related microbes.

“Some of the microbes we know come from dogs themselves,” said Menninger. “Some of these bacteria come from the outdoor environment, such as dogs bringing bacteria from the soil and into homes.” 

The researchers were able to identify a few classes of bacteria linked to dogs, and certain microbial classes that may cause disease in humans, such as gingivitis and pneumonia.  However, genetic testing of the bacteria was not specific enough to determine whether any harmful strains were there.

All those germs tracked in on dirty paws don’t mean dog-free homes are necessarily healthier, though. While the researchers did not identify the specific species of bacteria living in each household, they were able to say that most of the organisms they found are not disease-causing – and may actually provide some benefits.

“We co-exist with bacteria and healthy, small exposures to bacteria do not pose any risk and might, on the other hand, be beneficial, as long as we keep a good hygienic environment,” said Dr. Rani Gereige, director of medical education at Miami Children's Hospital.  Gereige was not involved in the research.

A recent study found that exposure to a microorganisms from a pet during a child’s first year of life of life may help ramp up the immune system, lowering the risk of developing allergies later. 

“Research has actually shown that mothers who live with dogs while pregnant are less likely to have children with conditions like atopic dermatitis or to develop allergies,” said veterinarian Dr. Andy Roark of Greenville, S.C. 

Certain bacteria from dogs – such as salmonella and listeria -- can cause infections in humans, however, so it is important to be vigilant, he cautions.

“It is always a good idea for both adults and children to wash hands after playing with pets, especially before eating,” said Roark.

The study did not control for certain factors that could affect bacterial growth, such as household climate and cleanliness, and there were not enough homes with cats to accurately analyze the feline contribution to residential bacteria.  The researchers did not analyze whether certain dog breeds harbor more bacteria than others.

The microbes found throughout the different homes fell into three general groups: those that come from skin and live on surfaces we touch, such as door knobs and toilet seats; bacteria linked to food found in kitchens; and organisms found in places where dust gathers, such as television screens and moldings.

Menninger added that the research team is in the process of analyzing samples and other data from a total of 1,300 homes across the United States. 

“We know we have all these bacteria in our home,” said Menninger.  “Let’s learn to live with them.” 

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