Impact of routine surgical ward and intensive care unit admission surveillance cultures on hospital-wide nosocomial methicillin-resistant Staphylococcus aureus infections in a university hospital: an interrupted time-series analysis.

OBJECTIVES To determine whether a routine admission screening in surgical wards and intensive care units (ICUs) was effective in reducing methicillin-resistant Staphylococcus aureus (MRSA) infections-particularly nosocomial MRSA infections-for the whole hospital. METHODS The study used a single-centre prospective quasi-experimental design to evaluate the effect of the MRSA screening policy on the incidence density of MRSA-infected/nosocomial MRSA-infected patients/1000 patient-days (pd) in the whole hospital. The effect on incidence density was calculated by a segmented regression analysis of interrupted time series with 30 months prior to and 24 months after a 6 month implementation period. RESULTS The MRSA screening policy had a highly significant hospital-wide effect on the incidence density of MRSA infections. It showed a significant change in both level [-0.163 MRSA-infected patients/1000 pd, 95% confidence interval (CI): -0.276 to -0.050] and slope (-0.01 MRSA-infected patients/1000 pd per month, 95% CI: -0.018 to -0.003) after the implementation of the MRSA screening policy. A decrease in the MRSA infections by 57% is a conservative estimate of the reduction between the last month before (0.417 MRSA-infected patients/1000 pd) and month 24 after the implementation of the MRSA screening policy (0.18 MRSA-infected patients/1000 pd). Equivalent results were found in the analysis of nosocomial MRSA-infected patients/1000 pd. CONCLUSIONS This is the first hospital-wide study that investigates the impact of introducing admission screening in ICUs and non-ICUs as a single intervention to prevent MRSA infections performed with a time-series regression analysis. Admission screening is a potent tool in controlling the spread of MRSA infections in hospitals.