A couple kisses during sunset by the island of Koh Tao September 20, 2014.Reuters

A 10-second kiss may give you 80 million bacteria, a new study says.

There is no dispute over the fact that kissing promotes transmission of bacteria.

Making the point clearer, a team of researchers from Netherlands initiated to calculate the total number of bacteria exchanged during a single kissing episode and found that kissing at least nine times a day was enough to make composition of oral bacteria in couples similar.

For the study, Remco Kort and colleagues from Micropia and TNO studied at 21 couples. As part of the research, the couples completed a questionnaire on kissing. They answered questions related to their kissing frequency and intimacy involved in it. Swab samples collected from the participants were used to determine oral bacteria composition in saliva and on their tongues.

To provide more evidence, the researchers assigned one couple from each group to drink a probiotic drink with Lactobacillus and Bifidobacteria and kiss their partner. After the intimate kissing episode, researchers found higher levels of the probiotic bacteria in partners who did not take the probiotic drink.

"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 cultures," lead author of the study, Kort from TNO, who is an adviser to the Micropia museum of microbes, said in a news release.

"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."

Additionally, according to the researchers, sharing the same lifestyle, diet and personal habits also can lead to similar oral bacteria composition on tongue. Proving this, partners had the same tongue microbiota which didn't change with kissing.

Findings of the study have been reported in journal Microbiome.