What are the symptoms and treatment options for Methicillin-resistant Staphylococcus aureus (MRSA) infections?

MRSA Symptoms and Treatment

MRSA causes a wide spectrum of infections ranging from simple skin abscesses and cellulitis to life-threatening invasive disease including bacteremia, endocarditis, necrotizing pneumonia, bone and joint infections, and sepsis syndromes. 1

Clinical Manifestations

Skin and Soft Tissue Infections (Most Common)

• Simple purulent lesions present as abscesses, boils, or furuncles with localized warmth, erythema, pain, and purulent drainage—these are the most frequent presentation of community-acquired MRSA 1
• Cellulitis manifests as acute inflammation of the dermis and subcutaneous tissue with warmth, erythema, pain, lymphangitis, and frequently systemic symptoms including fever and elevated white blood cell count 1
• Complicated soft tissue infections can progress to pyomyositis, necrotizing fasciitis, or mediastinitis as complications of deeper infections 1

Invasive Disease (High Mortality)

• Bacteremia accompanies 75% of invasive MRSA cases and can seed multiple organs 1
• Endocarditis with myocardial, perinephric, hepatic, and splenic abscesses 1
• Necrotizing pneumonia with cavitary lesions, often arising from hematogenous spread 1, 2
• Bone and joint infections including osteomyelitis with subperiosteal abscesses, venous thrombosis, and sustained bacteremia 1
• Severe ocular infections including endophthalmitis 1
• Sepsis syndromes including toxic shock, purpura fulminans, and Waterhouse-Friderichsen syndrome 1

Treatment Approach

For Simple Skin Abscesses

• Incision and drainage is the primary treatment—antibiotics are not needed if induration and erythema are limited only to the defined abscess area without extension beyond borders or into deeper tissues 1
• For small purulent lesions in healthy patients, drainage alone may be sufficient 3

For Cellulitis Without Abscess

Mild, early cellulitis in patients without comorbidities:

• Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets twice daily for 5-10 days is the preferred first-line oral agent in MRSA-prevalent areas 4
• Critical limitation: TMP-SMX lacks activity against β-hemolytic streptococci, so it should NOT be used for non-purulent cellulitis where streptococcal coverage is essential 4

Alternative oral options:

• Clindamycin 300-450 mg three times daily provides dual coverage for both MRSA and streptococci as a single agent, making it ideal when both pathogens are suspected 5, 4
• Doxycycline 100 mg twice daily or minocycline 200 mg initially, then 100 mg twice daily are effective alternatives with 83-100% clinical cure rates 4

For Severe or Complicated Infections Requiring Hospitalization

• Vancomycin IV is the drug of choice due to low cost, efficacy, and safety for complicated skin and soft tissue infections, bacteremia, and endocarditis 3
• Daptomycin 6 mg/kg IV once daily (some experts recommend 8-10 mg/kg for severe infections) is an alternative for bacteremia and endocarditis 1
• Linezolid, tigecycline, telavancin are additional options for severe infections 1, 3

For Bacteremia and Endocarditis

• Uncomplicated bacteremia: Vancomycin or daptomycin for at least 2 weeks, with documented clearance of bacteremia on repeat cultures 2-4 days after initial positive cultures 1
• Complicated bacteremia or endocarditis: 4-6 weeks of IV vancomycin or daptomycin (6-10 mg/kg daily), with transesophageal echocardiography recommended for all adult patients 1
• Do NOT add gentamicin or rifampin to vancomycin for bacteremia or native valve endocarditis 1

For Pneumonia with Empyema

• Antimicrobial therapy against MRSA must be combined with drainage procedures 1

For Neonates

• Localized disease in full-term neonates: Topical mupirocin may be adequate 1
• Premature/very low-birthweight infants or extensive disease: IV vancomycin or clindamycin initially until bacteremia is excluded 1

Management of Recurrent Infections

Personal Hygiene Measures

• Maintain regular bathing and hand cleaning with soap and water or alcohol-based gel, particularly after touching infected skin 1
• Avoid reusing or sharing personal items (razors, linens, towels) that contacted infected skin 1

Environmental Hygiene

• Focus cleaning on high-touch surfaces (counters, door knobs, bathtubs, toilet seats) using commercially available cleaners according to label instructions 1

Decolonization Strategies (When Hygiene Measures Fail)

• Nasal decolonization: Mupirocin twice daily for 5-10 days 1
• Combined approach: Mupirocin nasal decolonization PLUS topical body decolonization with chlorhexidine for 5-14 days or dilute bleach baths 1
• Evaluate and potentially decolonize symptomatic household contacts; consider decolonization of asymptomatic contacts if ongoing transmission occurs 1

Critical Pitfalls to Avoid

• Never use beta-lactam antibiotics alone (penicillins, cephalosporins)—they are completely ineffective against MRSA 4
• Never use rifampin as monotherapy or adjunctive therapy for skin infections due to rapid resistance development 5, 4
• Never use fluoroquinolones for MRSA infections—they are not adequate despite approval for uncomplicated cellulitis 1
• Avoid clindamycin if local resistance rates are high or if inducible resistance (D-test positive) is present, and be aware of increased Clostridioides difficile infection risk 4
• Failure to drain abscesses leads to treatment failure regardless of antibiotic choice 4
• Always obtain cultures from purulent drainage before starting antibiotics to confirm MRSA and guide therapy 5, 4
• Reassess within 48-72 hours—if no improvement occurs, consider alternative antibiotics or drainage 5