Clinical Manifestations of MRSA on the Skin
MRSA skin infections typically present as abscesses characterized by marked tissue necrosis and little or no purulent exudate, often accompanied by surrounding cellulitis. 1, 2
Common Presentations of MRSA Skin Infections
Primary Manifestations
Abscesses: The most common presentation of MRSA on the skin 1, 3
- Often appear as erythematous, tender, fluctuant nodules
- Characterized by significant tissue necrosis
- May have minimal purulent drainage when incised 2
- Frequently surrounded by cellulitis
Furuncles and Carbuncles: 1
- Furuncles (boils): Inflammatory nodules with overlying pustules through which hair emerges
- Carbuncles: Coalescent inflammatory masses with pus draining from multiple follicular orifices
- Commonly develop on the back of the neck, especially in individuals with diabetes
Cellulitis: 1
- Diffuse, spreading infection of the dermis and subcutaneous tissue
- Presents with erythema, warmth, tenderness, and induration
- MRSA cellulitis is typically more localized compared to streptococcal cellulitis
- May have accompanying systemic symptoms (fever, tachycardia)
Impetigo: 1
- Highly contagious infection of superficial epidermis
- Characterized by discrete purulent lesions
- CA-MRSA is increasingly identified as a causative agent
Distinguishing Features of MRSA Skin Infections
- Tissue Necrosis: More pronounced than in methicillin-sensitive S. aureus infections 2
- Resistance to Initial Treatment: Often fails to respond to beta-lactam antibiotics 2, 3
- Rapid Progression: Can quickly evolve from small lesions to larger abscesses 4
- Recurrence: Higher tendency to recur compared to other skin infections 1
- Multiple Lesions: May present with multiple sites of infection 4
High-Risk Populations
- Young, healthy individuals, particularly athletes 4
- Children in daycare settings 5
- Individuals in crowded living conditions 1
- Participants in contact sports 4
- Individuals with prior MRSA infections 1
Warning Signs of Invasive MRSA Infection
- Systemic inflammatory response syndrome (SIRS) 1, 6
- Altered mental status 1
- Hemodynamic instability 1
- Rapidly spreading erythema or induration 1
- Crepitus or bullae formation (suggesting deeper infection) 1
- Failure to improve within 48-72 hours of initial treatment 6
Common Locations
- Axillary regions 4
- Buttocks 4
- Thighs 4
- Areas subject to friction, shaving, or minor trauma 1
- Nasal passages (colonization rather than infection) 1
Diagnostic Considerations
- Physical examination typically reveals erythema, tenderness, and induration 1
- Cultures should be obtained from purulent drainage to confirm MRSA and determine antibiotic susceptibility 1, 4
- Blood cultures are recommended for patients with severe systemic features 1
Potential Complications
MRSA skin infections can progress to more serious conditions if not properly treated:
- Invasive infections including bacteremia 7
- Necrotizing fasciitis 1
- Osteomyelitis or septic arthritis 7
- Necrotizing pneumonia 7
- Infective endocarditis 7
Clinical Pearls
- The presence of marked tissue necrosis with minimal purulent drainage in an abscess should raise suspicion for MRSA 2
- Failure to respond to beta-lactam antibiotics is a key clinical clue for MRSA infection 2, 3
- Adequate incision and drainage is critical for successful treatment of MRSA abscesses 3
- Early recognition and appropriate treatment are essential to prevent progression to invasive disease 7
- Consider MRSA in recurrent skin infections, especially in athletes or those in close-contact environments 4
Remember that proper identification of MRSA skin infections is crucial for appropriate management and prevention of transmission to others.