Treatment of Scalp Infection with Staphylococcus aureus and Staphylococcus lugdunensis
For a scalp infection with drainage growing both S. aureus and S. lugdunensis, perform incision and drainage if an abscess is present, and initiate empiric antibiotic therapy covering methicillin-resistant S. aureus (MRSA) with either oral clindamycin, trimethoprim-sulfamethoxazole (TMP-SMX), or doxycycline, then narrow therapy based on culture susceptibilities. 1
Initial Management Approach
Surgical intervention is the priority. If the scalp drainage represents an abscess or purulent collection, incision and drainage is the primary treatment and may be sufficient alone for simple abscesses 1. However, antibiotic therapy is indicated when any of the following are present:
- Multiple sites of infection or extensive disease 1
- Systemic signs (fever >38°C, tachycardia >90 bpm, elevated WBC >12,000 or <4,000) 1
- Surrounding cellulitis beyond the abscess 1
- Difficult to drain location (scalp qualifies as this may involve hair-bearing areas) 1
- Immunocompromised state 1
Empiric Antibiotic Selection
Start with MRSA coverage empirically because community-associated MRSA is now prevalent in purulent skin infections, and you cannot distinguish methicillin-susceptible from methicillin-resistant strains clinically 1.
Oral Options for Outpatient Treatment:
- Clindamycin 300-450 mg three times daily (covers both MRSA and streptococci, though local resistance rates should be <10%) 1
- TMP-SMX 1-2 double-strength tablets twice daily (excellent MRSA coverage but does NOT cover streptococci—add a beta-lactam if concerned about strep) 1
- Doxycycline 100 mg twice daily (good MRSA coverage, avoid in children <8 years) 1
Intravenous Options if Hospitalization Required:
- Vancomycin 15-20 mg/kg IV every 8-12 hours (first-line for severe MRSA infections) 1
- Linezolid 600 mg IV/PO twice daily 1
- Daptomycin 4 mg/kg IV once daily 1
Tailoring Therapy Based on Culture Results
If Methicillin-Susceptible S. aureus (MSSA):
Switch to cephalexin 500 mg four times daily or dicloxacillin 500 mg four times daily 1. These beta-lactams are superior to vancomycin for MSSA 1.
If S. lugdunensis is Penicillin-Susceptible:
Penicillin G or a penicillinase-resistant penicillin (oxacillin/flucloxacillin) is optimal 2. S. lugdunensis remains susceptible to most antibiotics with 74.6% susceptible to penicillin G in recent studies, and penicillin G shows threefold lower MICs than oxacillin for susceptible strains 2. Methicillin resistance in S. lugdunensis is rare but does occur 2.
If MRSA Confirmed:
Continue the empiric MRSA-active agent selected above based on susceptibilities 1. Do not use TMP-SMX as monotherapy if any concern for streptococcal co-infection exists, as streptococci are intrinsically resistant 1.
Duration of Therapy
Treat for 5-7 days for uncomplicated skin and soft tissue infections after adequate drainage, adjusting based on clinical response 1. Longer courses (7-14 days) are warranted if:
- Deep tissue involvement is present 1
- Systemic illness persists 1
- Inadequate source control was achieved 1
Critical Pitfalls to Avoid
Do not use TMP-SMX alone if there is surrounding cellulitis without purulence, as this may represent streptococcal infection which is intrinsically resistant to TMP-SMX 1. In nonpurulent cellulitis, beta-lactam therapy (cephalexin or dicloxacillin) targeting streptococci is preferred 1.
Reassess at 48-72 hours. If the patient worsens or fails to improve despite appropriate drainage and antibiotics, consider 1:
- Deeper infection (osteomyelitis of skull if overlying bone involvement)
- Resistant organism
- Inadequate source control
- Alternative diagnosis
S. lugdunensis behaves more aggressively than typical coagulase-negative staphylococci, with virulence similar to S. aureus, particularly in causing endocarditis 1, 2. If bacteremia develops, evaluate for endocarditis and treat accordingly with prolonged therapy 1.