MRSA: What the Word Actually Means, and What It Does Not

Being told a culture grew MRSA lands badly. The word has been attached to “superbug” headlines for twenty years, and people reasonably assume they have caught something exotic and dangerous.

What MRSA actually describes is narrower and less frightening than that. It is ordinary staph, a bacterium that lives harmlessly on the skin and in the nose of roughly a third of people, which happens to be resistant to one family of antibiotics. The infection is the same infection. The list of drugs that will treat it is shorter.

What the letters mean

Methicillin-resistant Staphylococcus aureus. Methicillin is an old antibiotic no longer used, and it survives in the name as shorthand for a whole family: the penicillins and the related drugs that would normally be first choice for a staph infection. Resistance to one predicts resistance to the others.

That is the entire meaning of the word. It says which antibiotics will not work. It says nothing about how aggressive the infection is, how deep it has gone, or how worried anyone should be, all of which come from examining the patient rather than reading the report.

What a MRSA result changes, and what it does not

	Ordinary staph	MRSA
Which antibiotic	Penicillin family, usually oral	A different class; sometimes intravenous
Whether drainage is needed	Often, for an abscess	Equally often; unchanged
How long treatment runs	Depends on the site	Depends on the site; unchanged
How dangerous it is	Depends where it is	Depends where it is; broadly similar
Precautions in hospital	Standard	Contact precautions may be added
What it means for your household	Basic hygiene	Basic hygiene, applied more carefully

The row people expect to differ is the fourth one. For a skin infection treated with the right drug, MRSA is not meaningfully more dangerous than ordinary staph. What makes staph dangerous is reaching the bloodstream, a joint or a heart valve, and that is true of both.

Two quite different MRSA stories

The distinction that matters clinically is where it was acquired, because the two behave differently and turn up in different people.

• Community-associated MRSA typically causes skin and soft-tissue infections in otherwise healthy people. It often presents as a boil or abscess that someone is convinced is a spider bite.
• Healthcare-associated MRSA occurs in people with recent hospital stays, surgery, catheters or dialysis, and shows up in wounds, the bloodstream and around implanted devices.

The spider-bite conviction is worth naming. A painful, rapidly growing lump with a central point is far more often a staph abscess than a bite. Our article on animal and human bites covers what genuine bites actually look like, and cellulitis covers the spreading redness that sometimes accompanies it.

Treatment, and the part antibiotics do not do

For a skin abscess, the single most important treatment is drainage. That is not a preliminary step before the real treatment; for many abscesses it is the treatment, and antibiotics are an adjunct. An abscess that is not drained will not reliably resolve on antibiotics however carefully they are chosen.

Where antibiotics are needed, several oral options work against community-associated MRSA. Deeper infections, and anything involving the bloodstream, bone or a prosthesis, are treated intravenously and for considerably longer, which is often arranged through outpatient IV antibiotics rather than in hospital.

• Do not squeeze or dig at an abscess; it pushes infection deeper
• Keep it covered with a clean dry dressing until it has healed
• Finish the course you were given, for the reasons in our article on antibiotic resistance
• Go back if the redness is spreading, not shrinking, after 48 hours
• Deep infections in bone or joints are a different undertaking; see bone and joint infections

Why resistance happened here in the first place

Staph acquired this resistance the way bacteria usually do: it was exposed to the antibiotic repeatedly, and the strains that could survive it were the ones left to multiply. That process began within a few years of the drug being introduced, and it has been going on ever since.

This is the practical case for not taking antibiotics that cannot help you. Every unnecessary course applies the same selective pressure, in your own body and in the community, and MRSA is simply the most familiar name for the result. Our article on antibiotic resistance sets out how that works in more detail.

Carrying it is not the same as being infected

A significant number of people carry MRSA in their nose or on their skin without any infection at all. Colonization is not illness, does not cause symptoms, and is not treated in most circumstances.

Decolonization, usually a nasal ointment and antiseptic washes, is used in specific situations: before certain operations, or when someone has repeated infections. It is not routine, it does not always hold, and using it indiscriminately breeds resistance to the very treatments it relies on.

What actually prevents spread

MRSA spreads by contact, most often through hands and shared items rather than through the air. The measures that work are unglamorous and effective.

• Wash hands properly, and use sanitizer when soap is not available
• Keep any wound covered until it has healed
• Do not share towels, razors, or bar soap
• Wash towels and bed linen in hot water and dry them thoroughly
• Wipe down shared gym equipment before and after use
• Cover cuts before training or playing contact sports

Households where one person has a MRSA infection do not need to be disinfected top to bottom. Routine cleaning of surfaces that hands touch, plus the list above, is what is actually recommended.

When it warrants a specialist

• Infections that keep coming back despite correct treatment
• Any MRSA found in the bloodstream, which is always a serious matter
• Infection around a joint replacement, pacemaker or other implanted device
• Wounds that are not healing, which our article on why some wounds do not heal covers
• Infections in people with diabetes, particularly foot ulcers
• A reported penicillin allergy narrowing the options further

Resistant organisms are a large part of what an infectious disease practice does, from choosing the drug to arranging the monitoring. Our article on when to see an infectious disease specialist sets out what that assessment adds, and you can reach us through the contact page.

Frequently asked questions