The "short course of IV antibiotics" can be 16 weeks with an intravenous PIC line, which requires great care, since it itself is a delivery device to your heart and bloodstream and comes into contact with additional bacteria.
Yes the bacteria can be common. The problem, as others have mentioned, is that once in the bloodstream, since it is resistant to common antibiotics, it is tough to get rid of and easy to spread. This is different than "flesh-eating bacteria" in that it might not eat your arm, but it's much harder to kill.
This can be especially dangerous for anyone with any metal in the body - a screw in the ankle, a plate in the arm. The bacteria tends to stick to metal really well, and can create a tough membrane. Since there isn't a blood supply in the metal, it is much harder for white blood cells or antibiotics in the bloodstream to get to it. It can hunker down while you go through the antibiotic treatment, and then when you look out the second floor window it's gotten up out of the bushes and walked away, sharpening its knives.