While the infections that cause it vary, the pathogens don’t literally eat the flesh but rather excrete toxins that destroy tissue, causing the condition. Fortunately, not all cases of staph and MRSA turn into flesh-eating necrosis, but doctors can’t actually tell which strains and cases will eventually turn into a condition that eats away at the flesh, so it’s better to treat all situations involving these bacteria as if they were about to become necrotic. Even more terrifying than having this bacterium secrete toxins which eat away at your flesh while you wait helplessly for it to go away, or for your treatments to work, is that beyond just skin, ligament, muscle, and other soft tissues, the disease can eventually spread down to the bone and begin to eat away at that, too.