[Natsu]

The article gives this as the explanation of how it is supposed to work:

  BCS3-LI has four main genetic modifications:

  It produces a weak antibiotic, mutacin-1140, which kills competing oral bacteria.
  It’s immune to mutacin-1140, so it doesn’t kill itself.
  It metabolizes sugar through a different chemical pathway that ends in alcohol instead of lactic acid.
  It lacks a peptide that its species usually uses to arrange gene transfers with other bacteria.

  The antibiotic helps it win the Darwinian competition in your mouth to become King Of The Oral Bacteria. The alcohol metabolism means it won’t produce lactic acid (and so won’t cause tooth decay). The peptide knockout prevents it from transferring genes back and forth with other bacteria that might either inactivate it or leak its advantage.

[Retric]

> It produces a weak antibiotic, mutacin-1140, which kills competing oral bacteria.

That alone isn’t enough for long term colonization as it’s not the only bacteria resistant to mutacin-1140.

[Natsu]

There's also a graph claiming to show colonization results. I don't know how good it is, but it's supposedly actual experimental data.

[extraduder_ire]

> It metabolizes sugar through a different chemical pathway that ends in alcohol instead of lactic acid.

It'd be quite funny to live in a future where cavities don't exist, but breathalysers are useless. (without rinsing your mouth out first, I guess) Hopefully it doesn't dry out gums and cause gum disease.

[MostlyStable]

The article extensively talks about the amount produced. While it has not been tested against breathalyzers, it is producing so little alcohol that it seems unlikely to be a problem. The claim in the article is that, across 24 hours, you might consume a few miligrams of alcohol, as compared to "if you swallowed 1/10th of your mouthwash, that would be ~200 milligrams of alcohol". So across the entire day, you are producing a couple orders of magnitude less alcohol than is in 1/10th of a mouthwash treatment (or 1/5th I guess if you use it twice a day).