What is the evidence for routine screening of hospitalized patients for Methicillin-resistant Staphylococcus aureus (MRSA) and Vancomycin-resistant Enterococcus (VRE)?

Evidence for Routine Screening of Hospitalized Patients for MRSA and VRE

Targeted screening of high-risk patients for MRSA and VRE is recommended rather than universal screening of all hospitalized patients, with screening particularly indicated for ICU patients, oncology patients, transplant recipients, and those hospitalized for >5-7 days. 1

Rationale for Screening

• Screening helps identify colonized patients early, allowing for prompt implementation of infection control measures to prevent transmission
• Environmental contamination with MRSA and VRE occurs during patient care and increases transmission risk to subsequent room occupants 2
• Prior room occupancy by MRSA or VRE-positive patients increases acquisition risk by approximately 40% for subsequent patients 2

Recommended Screening Approach

Who to Screen

• High-risk patients:
  • ICU patients
  • Oncology patients
  • Transplant recipients
  • Patients hospitalized >5-7 days
  • Patients transferred from facilities with known MRSA/VRE presence 3, 1
• Roommates of newly identified MRSA/VRE-positive patients 1

Screening Methods

• For VRE:

  • Stool or rectal swab cultures are recommended as intestinal colonization is common 3, 1
  • Use selective media containing vancomycin to improve detection efficiency 3

• For MRSA:

  • Direct inoculation of pooled nose, throat, and perineal swabs on MRSA-selective chromogenic agar 4
  • Confirmation of presumptive colonies by latex agglutination for penicillin-binding protein 2a 4
  • PCR methods are available for same-day results but are more costly 4

Frequency of Screening

• For hospitals where MRSA/VRE have not been detected:

  • Periodic susceptibility testing on samples of enterococcal isolates, especially from high-risk patients 3
  • Hospitals processing many specimens may test only 10% of isolates every 1-2 months 3
  • Hospitals processing fewer specimens may need to test all isolates during survey periods 3

• After MRSA/VRE detection:

  • All enterococcal isolates should be routinely screened for vancomycin resistance 3
  • Intensified screening to identify colonized patients earlier 3, 1

Management After Positive Screening

1. Immediate notification of:

   • Patient's primary caregiver
   • Patient-care personnel
   • Infection control personnel 3

2. Implementation of infection control measures:

   • Patient isolation in private rooms or cohorting with other positive patients
   • Contact precautions (gloves, gowns)
   • Strict hand hygiene with antiseptic soap or waterless antiseptic agent
   • Dedicated medical equipment or proper cleaning between patients 1

3. Environmental considerations:

   • Verify adequate cleaning and disinfection procedures
   • Consider environmental cultures before and after room cleaning 1

Impact of Screening Programs

• Routine MRSA screening in vascular surgery has been associated with significant reductions in:

  • Wound infection rates (from 55.6% to 22.4% in elective admissions)
  • Amputation rates (from 27.8% to 9% in elective admissions)
  • Mortality (from 16.7% to 9% in elective admissions) 5

• Over 100 studies have reported successful control of MRSA infection and 38 have reported controlling VRE infection through active surveillance and isolation measures 6

Common Pitfalls and Caveats

• Fully automated methods of testing enterococci for vancomycin resistance can be unreliable 3
• PCR tests, while rapid, have relatively high false-positivity rates and lack definitive evidence of clinical cost-effectiveness 4
• Eradication becomes increasingly difficult and costly once MRSA/VRE become endemic on a ward or spread to multiple wards 3
• Discontinuing isolation precautions should follow stringent criteria (e.g., at least three consecutive negative results ≥1 week apart from multiple body sites) 1
• Medical records of previously colonized patients should be flagged to ensure prompt isolation upon readmission 1

Institutional Approach

• Successful control requires a collaborative, institution-wide, multidisciplinary effort
• Quality assurance/improvement departments should be involved to identify and address systemic issues
• Establish monitoring systems for both process measures (compliance with precautions) and outcome measures (colonization rates) 3, 1