I heard about a guy who got injured around his toenail in a beach. People didn't know what to do and did something wrong (and it got infected) which lead to amputations, of his toe first, then foot, then his leg below the knee and then above the knee. I was very young when I heard this and it scared the shit out of me.
ETA: can some medfag explain what are MRSA and staph?
If a real question: MRSA is a staph infection, but not all staph infections are MRSA.
Staph infections are anything involving staphylococcus bacteria. This is a group of bacteria including many species (just named for being round clusters), so any of those species could be a staph infection, but the most common culprit in humans is staphylococcus aureus (s. aureus).
A good percentage of us have s. aureus on us constantly, and in it's garden variety form it is usually harmless. It happens to be an adaptive bacteria able to survive with or without oxygen (facultative anaerobe), so it can grow in unique places. Normally they are only an issue in mass or in immunocompromised people.
Bacteria can pick up little extra traits by a few means, and those can add features that make the bacteria more damaging, more infectious, or antibiotic resistant. These added traits can cause things like simple sinusitis, pimples, or food poisoning (what most people would call a staph infection). Bacteria can also pass their traits to other bacteria.
When it picks up antibiotic resistance as one of those bonus traits it becomes MRSA (methicillin resistant s. aureus). Normal staph can get nuked by basics like penicillin (meth is similar), but now you have unstoppable growth. It's pretty common in medical settings, with livestock, and a good number of people even carry MRSA without symptoms in the general population too.
This means a munch could pick it up pretty easily when hospital surfing, demanding immunosuppressants, etc. Hand washing, gloves, sterile technique, etc can be damned good at preventing it, so when they play fast and loose and prod around in open wounds they increase risk. Play with medical waste for a bonus guarantee.