Up to 33% of the population carry Staphylococcus aureus at any time (nose, axilla, groin, skin).
A proportion are MRSA (methicillin-resistant strains), which pose a major challenge in healthcare due to limited antibiotic options and increased morbidity/mortality in vulnerable patients.
📖 About
- MRSA = S. aureus resistant to all beta-lactams (flucloxacillin, co-amoxiclav, carbapenems, methicillin).
- 💡 Resistance complicates therapy in hospitalised or immunocompromised patients.
- 👩⚕️ Healthcare workers may carry MRSA transiently → infection control is critical.
- Colonisation alone is harmless, but a reservoir for cross-infection.
🧬 Aetiology & Resistance Mechanism
- mecA gene → encodes altered penicillin-binding protein (PBP2a) with low affinity for beta-lactams.
- MRSA often carries additional resistance genes → macrolides, aminoglycosides, quinolones.
- Multidrug resistance → narrows therapy to glycopeptides, linezolid, daptomycin, ceftaroline.
👥 Patients at Risk
- 👵 Frail elderly, chronic disease
- 🏥 Long-stay/ICU patients
- 💉 Patients with invasive devices (lines, catheters, prostheses)
- 🩺 Surgical/orthopaedic patients with wounds
- 🛡️ Immunocompromised (chemo, HIV, steroids)
🧴 Suppression (Decolonisation) Regimen
- Body/Hair Wash: Daily antibacterial wash × 5 days (Octenisan®/Prontoderm®; Hibiscrub less well tolerated).
- Nasal Therapy: Mupirocin 2% ointment (Bactroban® nasal) TDS × 5 days.
➡️ If mupirocin-resistant → Naseptin® cream QDS × 10 days.
- Rationale: Reduce carriage pre-op or during admission → prevent invasive infection & nosocomial spread.
💉 Management of Active Infection
- Empirical substitution: Suspected MRSA infection → replace flucloxacillin with IV Teicoplanin (400 mg daily; 600 mg if >100 kg).
- Bacteraemia/Sepsis: IV Vancomycin (e.g., 15–20 mg/kg; ~1 g BD) infused over ≥100 min. Dose based on renal function & trough monitoring (target 15–20 mg/L for bacteraemia/endocarditis).
- Complicated infections:
- Endocarditis → Vancomycin + Rifampicin ± Gentamicin (microbiology guided).
- Bone/joint/prosthetic → prolonged IV therapy, surgical source control.
- Alternatives: Linezolid (oral/IV, good tissue penetration), Daptomycin (not for pneumonia), Ceftaroline (MRSA-active cephalosporin).
⚠️ Clinical Contexts
- 🫁 MRSA pneumonia: Severe, often post-influenza. Treat with Linezolid (better lung penetration than Vancomycin).
- 💔 Endocarditis: High mortality; prolonged IV Vancomycin ± surgery for valve involvement.
- 🦴 Osteomyelitis/Prosthetic joint infection: Biofilm formation → need prolonged therapy + surgical debridement/prosthesis revision.
Clinical Pearl:
Always distinguish colonisation (positive swab, no infection) from infection (systemic signs ± positive cultures).
Colonisation → suppression/decolonisation.
Infection → systemic antibiotics + source control.
🧼 Rigorous hand hygiene, barrier precautions, and patient screening underpin MRSA control in UK hospitals.
📚 References
- Public Health England (UKHSA) MRSA Screening & Management Guidance
- NICE Antimicrobial Prescribing Guidelines
- BTS & IDSA Guidelines on MRSA pneumonia/endocarditis
