Most probably it is infection by bacteria as it is filled by puss. If it does not contain puss then it will not be a infection. The MRSA is a resistant strain of staphylococcus. It can cause infections on skin especially on cuts and wounds. To treat it first have a incision on the blister and let the fluid come out. Then have bandage of topical antibiotic and take some oral antibiotic. I advise you to visit a doctor for incision and treatment. The outlook of MRSA and other infections is not different.
