I am involved with both. Primarily Staph aureus at the moment, but the I’ve worked with the cells of both (which was a little scary but entirely safe) and proteins from regular Staph aureus so far. Methicllin resistant strains (called MRSA – the media and scientists LOVE acronyms) are of interest because they withstand mankind’s best drugs, the penicillins, including methicillin, which was a drug made to beat regular penicillin resistance.
Outside of penicillin drugs, there’s not much else! Vancomycin is a different drug and can be used, but it’s great, with some awful side effects. On top of that, now vancomycin resistant strains are appearing – called VRSA.