Hospital-wide infection control practice and Meticillin-resistant Staphylococcus aureus (MRSA) in the intensive care unit (ICU): an observational study

OBJECTIVES To estimate trends in infection/colonisation with meticillin-resistant Staphylococcus aureus (MRSA) in an intensive care unit (ICU). DESIGN Observational study of results of ICU admission and weekly screens for MRSA. SETTING AND PARTICIPANTS All ICU admissions in 2001-2012. INTERVENTIONS ICU admissions were screened for MRSA throughout. In late 2006, screening was extended to the whole hospital and extra measures taken in ICU. MAIN OUTCOME MEASURES Prevalence of MRSA in ICU admissions and number acquiring MRSA therein. RESULTS In all, 366 of 6565 admissions to ICU were MRSA positive, including 270 of 4466 coming from within the hospital in which prevalence increased with time prior to transfer to ICU. Prevalence in this group was 9.4% (8.2-10.6) in 2001-2006, decreasing to 3.4% (2.3-4.5) in 2007-2009 and 1.3% (0.6-2.0) in 2010-2012, p < 0.001, due to decreased prevalence in those spending >5 days on wards before ICU admission: 18.9% (15.6-22.2) in 2001-2006, 7.1% (4.0-10.2) in 2007-2009 and 1.6% (0.1-3.1) in 2010-2012, p < 0.001. In addition, 201 patients acquired MRSA within ICU, the relative risk being greater when known positives present: 4.34 (3.98-4.70), p < 0.001. Acquisition rate/1000 bed days decreased from 13.3 (11.2-15.4) in 2001-2006 to 3.6 (2.6-4.6) in 2007-2012, p < 0.0001. Of 41 ICU-acquired MRSA bacteraemias, 38 were in 2001-2006. The risk of bacteraemia in those acquiring MRSA decreased from 25% (18.1-31.9) in 2001-2006 to 6.1% (0-12.8) thereafter, p = 0.022. CONCLUSIONS Following better hospital-wide infection control, fewer MRSA-positive patients were admitted to ICU with a parallel decrease in acquisition therein. Better practice there reduced the risk of bacteraemia.