If you're a pet-owner who kisses your dog on the mouth, you might want to think twice.
A new study in the journal Archives of Oral Biology suggests that it's possible for disease-causing oral bacteria to be exchanged between dogs and their owners.
Japanese researchers examined dental plaque from 66 dogs, as well as dental plaque from 81 people from Japan who visited a dog-training school or animal clinic during 2011. They conducted analysis to find the presence of 11 disease-causing oral bacteria -- called "periodontopathic" species -- in the plaque.
They found that three kinds of disease-causing oral bacteria were especially prevalent in the dogs' dental plaque: Porphyromonas gulae, which was found in 71.2 percent of the dogs' samples; Tannerella forsythia, which was found in 77.3 percent of the dogs' samples; and Campylobacter rectus, which was found in 66.7 percent of the dogs' samples.
Meanwhile, those bacterial species were a little less common in humans, but present nonetheless: Porphyromonas gulae was found in 16 percent of the humans' samples; Tannerella forsythia was found in 30.9 percent of the humans' samples; and Campylobacter rectus was found in 21 percent of the humans' samples.
Porphyromonas gulae, in particular, was found in 13 of the humans, whose dogs also tested positive for this specific kind of bacteria, the researchers found. They also found a link between dogs and their human owners regarding the Eikenella corrodens and Treponema denticola kinds of bacteria.
"These results suggest that several periodontopathic species could be transmitted between humans and their companion dogs, though the distribution of periodontopathic species in both is generally different," the researchers wrote in the study.
However, Dr. Paul Maza, of the College of Veterinary Medicine at Cornell University, told Fox News last year that many of the bacteria in dogs' and cats' mouths are similar to that in humans' mouths.
"Because most of the bacteria and viruses in a dog's mouth are the same as in a person's mouth, it is safe to kiss a dog, just like a person. You can probably catch more from kissing a human than a dog or cat," Maza told Fox News.