Osculum Obscenum: One kiss can transfer 80 million bacteria


A kiss can be deadly if you mean it, said the Batman to the Catwoman. Maybe not deadly, but you won’t think a kiss is just a kiss anymore. A Dutch research team concluded that “French kissing is a great example of exposure to a gigantic number of bacteria in a short time.” Professor Remco Kort and colleagues from the Netherlands Organisation for Applied Scientific Research compiled data on the kissing behavior of 21 couples, including how often they kissed in the previous year and when they last kissed – hopefully not after they were out on a date in his daddy’s car, and they hadn’t driven very far.

Additionally, the researchers collected bacterial swab samples from the tongues and saliva of the volunteers before they kissed for 10 chronographed seconds. One of the couple’s members then drank a probiotic drink with an identifiable mix of bacteria. The coupled kissed again for another 10 seconds after which the scientists measured the volume of microorganisms transferred from one partner to the other; an average of 80 million in a single kiss. Studies have indicated more than 700 types of bacteria live in the mouth, but this research shows some are easier to transfer than others. Moreover, “only some bacteria transferred from a kiss seemed to take hold on the tongue,” said Kort, while saliva bugs appeared to change more quickly. It’s not all bad news, though. Experts say these populations may promote health, prevent disease, and build resistance.

“Intimate kissing involving full tongue contact and saliva exchange appears to be a courtship behavior unique to humans and is common in over 90% of known culture,” Kort said. “Interestingly, the current explanations for the function of intimate kissing in humans include an important role for the microbiota present in the oral cavity, although to our knowledge, the exact effects of intimate kissing on the oral microbiota have never been studied. We wanted to find out the extent to which partners share their oral microbiota, and it turns out, the more a couple kiss, the more similar they are.”

You know how couples who spend too much time together start acting alike? Well, “apparently, being with somebody for an extended amount of time and having a relationship leads to a similar collection of bacteria on the tongue,” Kort explained. The researchers collaborated with Micropia, the world's first museum of microbes in Amsterdam – not related to The Theatre of Small Convenience in England. The museum is currently holding the kiss-o-meter interactive exhibit. An increasing number of scientists are investigating the microbiome, a 100 trillion microorganism ecosystem in and on the human body. “Further research should look at the properties of the bacteria and the tongue that contribute to this sticking power,” Kort said. “These types of investigations may help us design future bacterial therapies and help people with troublesome bacterial problems.”

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