How soon after a boil happens will you get a staph infection or mrsa?

Staph/MRSA: are the causes of boils/abscesses, if that helps answer your question.

Already infected.: A boil IS an infection. You may already have staph (whether it is MRSA or regular staph) which could have caused it. There are other causes. Staph is present on everyone's skin. You can get MRSA from others if you don't have it now. You could have a non-MRSA staph causing your boil, and if it is open or draining can catch MRSA if you do not keep it covered and clean & safe from more germs.

It is infected: If it wasn't, you would not have the immune & inflammatory response to create the boil (/abscess). Depending on your health and personal susceptibility, it can stay local, or migrate and enter the bloodstream and cause systemic infection (/sepsis).

Cause: It is usually the cause of the boil so it is already present. Hope this helps. A culture can be taken from the boil which may need to be drained.

Boils: These are infections of the skin and subcutaneous tissue and more often than not, due to Staphylococcus aureus, the strains of which may or may not be resistant to methiciillin (or oxacillin). Occasionally there may be other pathogens involved, but this is very uncommon.

You already have it!: The boil itself is the result of the infection, it doesn't "get infected with the bugs you mentioned. The boil is a fancy name for an abscess- a puss-filled pocket that is the result of an ingrown hair that has become infected with bacteria- usually something like staph and in some cases, community-acquired methicillin resistant Staphyloccocus aureus (CA-MRSA). Hope this answers your question.