Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
MRSA colonisation and infection
Infectious diseases, microbiology and sexual health · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
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Severe MRSA infection
Shock, rapidly progressive skin necrosis, haemoptysis with cavitating pneumonia, persistent bacteraemia, prosthetic infection or a new murmur can indicate toxin-mediated or deep invasive MRSA.
Action: Use ABCDE and sepsis care, obtain blood and source cultures without delaying active intravenous treatment, involve microbiology and the relevant surgical team, drain or debride promptly, and institute IPC precautions.
Synopsis
Distinguish meticillin-resistant Staphylococcus aureus carriage from infection, secure cultures and source control, select site- and susceptibility-directed therapy, clear bloodstream infection rigorously, and apply proportionate decolonisation and infection prevention.
MRSA carries mecA or mecC-mediated altered penicillin-binding protein, making standard anti-staphylococcal beta-lactams ineffective despite otherwise typical S. aureus virulence.
Colonisation means MRSA is present on nose, throat, perineum, skin or a wound without attributable inflammation or systemic disease; systemic antibiotics are not used to sterilise carriage.
Culture blood and the true infection focus before antimicrobials when safe, then request full susceptibility because MRSA resistance beyond beta-lactams is variable.
An abscess needs incision and drainage; antibiotics are not routinely necessary after complete drainage of a small lesion below 5 cm without cellulitis, systemic response or immunodeficiency.
First-line treatment for severe MRSA skin and soft-tissue infection is intravenous vancomycin or teicoplanin with concentration-guided dosing; linezolid or daptomycin is an alternative.
MRSA pneumonia can be treated with intravenous vancomycin or linezolid 600 mg orally or intravenously every 12 hours; daptomycin must not be used because lung surfactant inactivates it.
MRSA bacteraemia needs repeat blood cultures to clearance, line and source review, echocardiography when indicated, at least 14 days for rigorously uncomplicated disease and longer for deep infection.
Decolonisation is an IPC-directed intervention, commonly nasal mupirocin 2% three times daily plus chlorhexidine 4% body wash daily for five days, with resistance and skin tolerance considered.
Key red flags
Persistent positive blood cultures beyond 48 to 72 hours on active therapy suggests uncontrolled source, endocarditis, infected thrombosis, prosthetic material or inadequate drug exposure.
Severe pain, bullae, skin anaesthesia, systemic toxicity or rapidly spreading necrosis requires immediate surgical exploration for necrotising soft-tissue infection.
Haemoptysis, leucopenia, shock and multilobar cavitating pneumonia after influenza can indicate Panton-Valentine leucocidin-associated disease and needs toxin-suppressing specialist therapy.
Back pain, focal bone or joint pain, new neurology or implanted hardware during bacteraemia suggests metastatic osteomyelitis, epidural abscess or prosthetic infection.
MRSA in urine without a urinary explanation should prompt blood cultures and evaluation for bacteraemia rather than reflex treatment as simple cystitis.
Severe immediate glycopeptide reaction, renal failure, thrombocytopenia or serotonergic interactions can change the safest anti-MRSA agent and require pharmacy review.
Bloodstream infection
Fever, rigors, hypotension or an otherwise unexplained inflammatory syndrome with MRSA in blood is always clinically significant.
Necrotising pneumonia
Rapid respiratory failure, haemoptysis, shock and cavitation, often after influenza in a younger person, suggests toxin-mediated severe disease.
Investigation priorities
01
First-line culture and susceptibilityFirst stepFirst line
Confirm MRSA at the infection focus and identify active oral and intravenous options.
Management branches
CULTURE FIRSTAssess colonisation versus infection
MRSA is detected from screening or a clinical specimen.
Identify the exact specimen and examine for pain, erythema, purulence, systemic illness or organ dysfunction; do not infer disease from the organism name.
Before antibiotics, obtain blood cultures when systemically unwell and a deep or sterile-site specimen from the focus when sampling is safe.
Review prior MRSA, antimicrobial exposure, devices, implants, surgery and healthcare contacts and notify the local IPC team.
Treat clinical infection according to site and severity; use decolonisation and screening only under the IPC or perioperative pathway.
Key medicines
VancomycinUse an intravenous weight-based loading and maintenance regimen from the local AUC or concentration protocol, commonly beginning around 15 to 20 mg/kg every eight to twelve hours with renal adjustment.Measure exposure early, monitor renal function and infusion reaction, review MIC and source control with persistent bacteraemia, and do not use oral vancomycin for systemic MRSA.
TeicoplaninFor severe infection, a common regimen is 12 mg/kg intravenously every 12 hours for three to five loading doses, then 12 mg/kg once daily with level-guided renal adjustment.Adequate loading is essential; monitor pre-dose levels, renal function, blood count and liver tests, and avoid underdosing deep or bloodstream infection.
Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.