Should I be worried if my wife has mrsa?

Usually Benign Bact. Probably not, hygiene. Staphylococcus aureus frequently present skin & respiratory tract, especially nose. Mrsa merely means resistant multiple abs. Control of bacteria, as with all, a function of immune system. Sa most commonly a commensal bacteria, but reality not good for marketing fear. Dietary choices, activities, emotions, any internal control affecting staph & immune function can change.
Can be serious. Mrsa (methicillin-resistant staph aureus) can range from mild and annoying (skin abscesses) to life threatening (pneumonia and sepsis). Many people are colonized with the bacteria (harboring it on their bodies) but never get sick. It can be transmitted from human contact, including at gyms and saunas.