405nm will actually kill MRSA in vivo, but it does not penetrate deeply enough to get to a colony that is located more than 0.1mm or so into the skin, less for pigmented skin. A 470nm laser will go further in, and thus be more useful.
However, you can use 405nm to clean out a superficial pseudomonas colony, as well as sterilizing surfaces that harbor such colonies (typically found in the kitchen, in bathrooms and a few other places). They tend to end up in your ear if you do get a colony, and that can be painful. After a few rounds of topical treatments, I decided to try it with a recurring outer ear colony. Worked like a charm. The doctor wishes he had a medical use approved unit. Make sure it's set to flashlight spread, though.
Incidentally, pseudomonas produces fluorescin, which is used in dye lasers. It is readily pumped by a bluray diode, but homebrew folks usually pump it with a nitrogen TEA laser instead, due to the higher power output. You can buy fluorescin at a chemistry supply store. Don't grow your own. For low powers, I think a Venturi pump, a capillary glass, a small tube, the mirrors and a marker pen should be sufficient to see some action.
I'm taking the article to extremes but it sounds good at least for one type of bacteria.
