What's "private" about your DNA? You spread it everywhere daily. Anyhow these tests are basically pseudo-science. If you like pseudo-science, like probiotics and so, go for it.
"To this aim, we conducted a prospective longitudinal interventional study in 21 healthy human volunteers not consuming probiotics"
Out of 21 they selected 15 for the study.
A) they don't identify which bacteria is in the Yogurt. B) Lab testing has shown that yogurt is a terrible medium for supporting probiotics so most or all of them are dead by the time you eat it. C) Probiotics in foods don't typically establish themselves in your gut, it already is saturated with bacteria ideally suited to the environment. You would need frequent and high concentrations to disrupt that.