What determines if one of the “flesh-eating” bacteria inflicts toxins that eat up muscle?
smithese
I mean a lot of the bacteria strains capable of this are common bacteria that cause other diseases but don’t cause flesh eating syndrome most of the time. What sets off the bacteria in rare instances to release toxins to destroy muscle tissue?

almost any of the flesh eating bacteria are capable of producing toxins that destroy muscle (along with other) tissue. what keeps the bacteria in check is the location of the infection and the immune response, and toxin clearing capabilities of the body. In immunodeficient, or otherwise impaired individuals, the body cannot mitigate the bacterial damage.