Question: Is Streptococcus pyogenes really a life threatening bacteria? Also, how does it eat your flesh without a digestive tract?

Hey there Pneumo.
S. pyogenes is a pretty nasty little guy. When it rocks up it is there to make you very sick and if it causes an invasive infection (i.e. gets into your body, specifically into your blood) then there is a 1 in 4 chance that you will die.
This is one of a few different flesh-eating bacteria but they all use relatively similar mechanisms to eat their way through. Bacteria do not have digestive tracts, they are only single cells, where would they put them? Instead they make toxins and enzymes that they export into the environment which break down the environment. The bacteria then soak up all that goodness. It would be like if you vomited stomach acid onto your burger, let it breakdown then suck the whole lot up with a straw.
In the case of S. pyogenes they make a toxin called a ‘beta-heamolysin’. This type of toxin looks like an upside down capital L. Several ‘Ls’ join together to make a ring with a lip that then finds a human cell to bind to. Once bound the ring punches down on the human cell like a hole-punch on the side of a balloon and all the stuff inside the cell leaks out like the water from the balloon. S. pyogenes then absorbs all the goodies from inside the popped cell.