What are the risk factors for Methicillin-resistant Staphylococcus aureus (MRSA) infections?

Risk Factors for MRSA Infection

Prior MRSA infection or colonization is the single strongest risk factor for developing MRSA infection, followed by recent hospitalization, nursing home residence, and recent antibiotic use. 1

Healthcare-Associated Risk Factors

Healthcare settings represent the most significant environment for MRSA acquisition and transmission. Key healthcare-associated risk factors include:

• Recent hospitalization (within previous 1-24 months) 1
• Nursing home or long-term care facility residence 1
• Recent antibiotic exposure (particularly beta-lactams, fluoroquinolones, or macrolides within past 3 months) 1
• Prolonged hospital stay (current duration >16 days) 1
• Presence of invasive devices, especially central venous catheters 1, 2
• Dialysis, particularly hemodialysis with central venous catheter access 1, 3, 4
• Prior surgery 4
• ICU admission 2

Among dialysis patients specifically, risk factors include:

• Temporary dialysis access (vs. permanent access) 3
• Lower serum albumin levels 3
• Chronic lung disease 3

Patient-Specific Risk Factors

Certain patient characteristics increase the likelihood of MRSA acquisition:

• Advanced age (≥75 years) 1
• Chronic comorbidities 1:
  • Diabetes mellitus
  • Chronic obstructive pulmonary disease
  • Immunosuppression
  • HIV infection
  • Chronic kidney disease 4
  • Hemiplegia 4
• Charlson score >5 points 1

Community-Associated Risk Factors

Community-associated MRSA (CA-MRSA) has distinct risk factors:

• Close contact with MRSA-colonized individuals 1
• Living in crowded conditions (correctional facilities, military barracks, homeless shelters) 1, 5
• Participation in contact sports 1
• Injection drug use 1
• Men who have sex with men 1
• Children <2 years old 1

Clinical Presentations Associated with Higher MRSA Risk

Certain clinical scenarios should raise suspicion for MRSA:

• Severe infection requiring ICU admission 1
• Septic shock 1
• Post-influenza-like illness 1
• Concurrent skin and soft tissue infection 1
• Presence of chronic skin lesions 6

Local Epidemiology Considerations

The local prevalence of MRSA significantly impacts the risk assessment:

• High local prevalence of MRSA is a risk factor itself 6
• Empiric MRSA coverage is recommended when local prevalence exceeds 20% of S. aureus isolates 1
• Presence of multiple MRSA-colonized patients in the same hospital unit increases risk for other patients 2

Prevention Strategies

For patients with identified risk factors, prevention strategies include:

• Appropriate hand hygiene
• Contact precautions for known MRSA carriers
• Decolonization in high-risk settings (e.g., pre-surgical, dialysis)
• Antimicrobial stewardship to reduce unnecessary antibiotic use
• Improved vascular access for hemodialysis patients to avoid central venous catheters 7

Common Pitfalls to Avoid

1. Failing to identify MRSA carriers: Screening high-risk patients (especially those with previous MRSA history) is crucial
2. Overuse of broad-spectrum antibiotics: This contributes to resistance development
3. Inadequate attention to central venous catheter care: Proper insertion and maintenance protocols are essential
4. Neglecting local epidemiology: MRSA prevalence varies significantly by region and facility
5. Focusing only on healthcare-associated risk factors: Community-associated MRSA has distinct risk factors that should not be overlooked

Understanding these risk factors allows for targeted screening, prevention strategies, and appropriate empiric antibiotic selection when MRSA infection is suspected.