Does xylitol kill all kinds of bacteria?
Xylitol does not kill any bacteria.

Xylitol is a sugar alcohol that bacteria happen to not be able to use as an energy source. In the absence of other sugars, bacterial growth slows. Therefore, its antimicrobial mechanism is bacteriostatic rather than bactericidal.

No antibiotic exists, or will ever exist, that kills or inhibits all kinds of bacteria.

One thing xylitol can kill is a dog – keep xylitol-containing products such as gum well out of their reach.