Universal surveillance for methicillin-resistant Staphylococcus aureus in 3 affiliated hospitals.

BACKGROUND The effect of large-scale expanded surveillance for methicillin-resistant Staphylococcus aureus (MRSA) on health care-associated MRSA disease is not known. OBJECTIVE To examine the effect of 2 expanded surveillance interventions on MRSA disease. DESIGN Observational study comparing rates of MRSA clinical disease during and after hospital admission in 3 consecutive periods: baseline (12 months), MRSA surveillance for all admissions to the intensive care unit (ICU) (12 months), and universal MRSA surveillance for all hospital admissions (21 months). SETTING A 3-hospital, 850-bed organization with approximately 40,000 annual admissions. INTERVENTION Polymerase chain reaction-based nasal surveillance for MRSA followed by topical decolonization therapy and contact isolation of patients who tested positive for MRSA. MEASUREMENTS Poisson and segmented regression models were used to compare prevalence density of hospital-associated clinical MRSA disease (bloodstream, respiratory, urinary tract, and surgical site) in each period. Rates of bloodstream disease with methicillin-susceptible S. aureus were used as a control. RESULTS The prevalence density of aggregate hospital-associated MRSA disease (all body sites) per 10,000 patient-days at baseline, during ICU surveillance, and during universal surveillance was 8.9 (95% CI, 7.6 to 10.4), 7.4 (CI, 6.1 to 9.0; P = 0.15 compared with baseline), and 3.9 (CI, 3.2 to 4.7; P < 0.001 compared with baseline and ICU surveillance), respectively. During universal surveillance, the prevalence density of MRSA infection at each body site had a statistically significant decrease compared with baseline. The methicillin-susceptible S. aureus bacteremia rate did not statistically significantly change during the 3 periods. In a segmented regression model, the aggregate hospital-associated MRSA disease prevalence density changed by -36.2% (CI, -65.4% to 9.8%; P = 0.17) from baseline to ICU surveillance and by -69.6% (CI, -89.2% to -19.6%]; P = 0.03) from baseline to universal surveillance. During universal surveillance, the MRSA disease rate decreased during hospitalization and in the 30 days after discharge; no further reduction occurred thereafter. Surveillance with clinical cultures would have identified 17.8% of actual MRSA patient-days, and ICU-based surveillance with polymerase chain reaction would have identified 33.3%. LIMITATION The findings rely on observational data. CONCLUSION The introduction of universal admission surveillance for MRSA was associated with a large reduction in MRSA disease during admission and 30 days after discharge.