Epidemiology of nosocomial infections caused by methicillin-resistant Staphylococcus aureus

Area of Science:

• Infectious Diseases
• Hospital Epidemiology
• Microbiology

Background:

• Hospital-acquired infections (HAIs) caused by methicillin-resistant Staphylococcus aureus (MRSA) are increasingly prevalent in the US.
• Outbreaks are frequently concentrated in critical care units.
• MRSA is endemic in most hospitals, with infected/colonized patients as the reservoir and healthcare worker hands as the primary transmission route.

Purpose of the Study:

• To identify the primary reservoir of MRSA within a hospital.
• To implement and evaluate control measures for a widespread MRSA outbreak.
• To assess the impact of interventions on MRSA prevalence and acquisition.

Main Methods:

• Utilized three surveillance methods: daily clinical laboratory data, monthly high-risk inpatient microbiology surveys, and identification of previously infected patients.
• Implemented control measures targeting identified reservoirs and transmission routes.
• Monitored MRSA prevalence and acquisition rates over a 12-month period post-intervention.

Main Results:

• Surveillance identified colonized/infected inpatients as the main reservoir, contributing to 38%, 31%, and 31% of new cases respectively.
• Post-intervention, a statistically significant decline in MRSA prevalence (p < 0.001) was observed.
• A significant reduction in MRSA acquisitions (p < 0.002) was also documented over the 12-month study period.

Conclusions:

• Infected and colonized inpatients are the major reservoir for MRSA in hospitals.
• Targeted surveillance and control measures can effectively reduce MRSA outbreaks and endemicity.
• Hand hygiene and environmental controls are crucial for preventing patient-to-patient transmission.