Is a dog’s mouth really cleaner that a human’s? Some say yes. Most experts believe you’ll be no worse for the wear from a smooch from your pooch. Some recent studies show that saliva from a dog’s mouth can actually kill certain types of bacteria. Researchers found that dog saliva killed E. coli and streptococcus canis, which are both harmful bacteria, that can make us sick. (Dog Science Review, 2005) When Bow-Wow Newsletter asked a veterinarian about the cleanliness of a dog’s mouth, he suggested that we must keep in min that a dog’s tongue serves as both a washcloth and toilet paper. (Bow-Wow Newsletter, 2003). As gross as this may seem, mounting evidence shows that dog saliva may have the ability to kill bacteria. In numerous studies, it has been shown that the infection rate for human bites was higher than for the infection for dog bites. The question remains – can dog saliva kill bacteria?
This means that if a person was bitten by another person, the chance of that wound getting infected is much greater than if the person was bitten by a dog. One possibility that might explain why human bites are more serious, and get infected more often than dog bites is that the bacteria that live in a dog’s mouth is specific to a dog, and specifically adapted to living in dogs and not in people. there are not too many species of bacteria that can live in more that one species. (Publication of Mammals, 2004) Still, can dog saliva kill bacteria?
Most dog germs are just dog germs and usually don’t cause harm to humans. Another possibility that may explain why a dog bite is less infectious that a human bite, is that the dog’s saliva might contain a specific chemical or enzyme that might kill bacteria or make it less dangerous. In a 1990 study that was done at the University of California, Davis, researchers found that when mother dogs licked their puppies’ mouths, and where the puppies nursed from, it kept the puppies free from disease, and that when dogs licked their own wounds, it did the same thing. Researchers are also exploring the idea that dog saliva might contain a form of antibiotic such as penicillin. A form of the streptococcus bacteria is one that has shown to have been killed after it came in contact with dog saliva. Could their saliva contain penicillin or a form of antibiotic that deactivates or kills certain bacteria? A person is much more likely to get sick or even get a serious illness from kissing a person than a dog. As a registered nurse, I have seen more that my share of infected bites that were caused by humans. I’ve seen few dog bites become infected. Yes, dogs can transmit some illness to humans, but this usually happens as a result of their vaccinations and medications not being current and up to date.
Anyway, for my daughters school science fair experiment, we set out to find out if dog saliva could actually kill bacteria, and this is what we found. First we collected 2 samples of bacteria from a library computer keyboard with 2 sterile cotton tipped applicators and placed the contaminated swabs back into their original wrappers. Next, we swabbed the inside of 2 sterile agar petri dishes. We then collected saliva from our male St. Bernard dog, Jeff and placed it into a sterile test tube. We then took another cotton tipped applicator and collected a sample of the dog saliva and placed it into one of the petri dishes that was contaminated with the computer keyboard bacteria. We closed the lid on both petri dishes and placed them in a warm environment for 2-3 days until bacteria started to grow. After 2-3 days, we checked the bacteria growth and compared the 2 samples to see if the one with the dog saliva contained the least amount of bacteria. Can dog saliva prevent bacteria? We were extremely surprised with the results of the experiment. No bacteria colonies grew in the agar plate petri dish that had been swabbed with the library keyboard bacteria to which the dog saliva was added. The petri dish that did not contain the dog saliva grew many bacterial colonies – 4 1.27 cm round circles, 1 .25 cm round circle, 8 .32 cm round circles and 72 circles that were too small to measure. Can dog saliva prevent bacteria? You be the judge.
I would like to acknowledge by beautiful and intelligent daughter, Stephanie for her work in conducting this fascinating experiment which won her a 1st place award at her school’s science fair and a special award and savings bond from the Illinois Professional Society of Microbiologists. Congratulations Steph!
Sources – University Of California, Davis – 1990 Study of Dogs Licking Their Own Wounds Keeps Them Free
VCA Animal Hospital
Vanderbilt University, 2001 Study – A Form Of Strep Bacteria Killed After Coming In Contact With Dog