GPAtlas🧭 When to suspect
Meticillin-resistant Staphylococcus aureus (MRSA) is a strain of S. aureus resistant to the beta-lactam antibiotics – including the penicillins (such as flucloxacillin) and the cephalosporins – which makes it harder to treat than ordinary staphylococcal infection. The single most important distinction in primary care is colonisation versus infection: around one in thirty people carry MRSA harmlessly on the skin or in the nose, and carriage alone does not warrant systemic antibiotics.
Suspect MRSA in any skin or soft tissue infection (SSTI) – redness, swelling, warmth, pus, a boil or an abscess – that fails to respond to standard empirical antibiotics. Risk is higher with recent contact with a healthcare facility (hospital or care home), chronic wounds or leg ulcers, indwelling devices (urinary catheters, intravenous (IV) lines, percutaneous endoscopic gastrostomy (PEG) tubes), recent antibiotics, immunosuppression, or known close contact with MRSA.
Recurrent or multiple boils and abscesses – particularly in otherwise fit, young people, those in close-contact sports, or household clusters – should prompt consideration of Panton-Valentine leucocidin (PVL)-associated S. aureus, which may be meticillin-sensitive (MSSA) or MRSA.
| Feature | Colonisation (carriage) | Infection |
|---|---|---|
| Clinical picture | No symptoms – bacteria present without harm | Local signs (redness, pus, abscess) ± systemic features |
| Systemic antibiotics | Not indicated | Indicated for genuine infection, guided by sensitivities |
| Primary action | Selective topical decolonisation and IPC where appropriate | Drain and swab, treat per sensitivities, safety-net |
|
🧠 Clinical pearl Think PVL when boils and abscesses recur or appear in several sites, especially in a fit young adult, a wrestler or rugby player, or where a household member or teammate has the same problem. PVL is a toxin carried by fewer than 2% of S. aureus isolates and can sit on either MSSA or MRSA – so request PVL testing specifically on the form, because the laboratory will not look for it routinely. |
Source: BSAC/BIA · UKHSA
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