Mortality after Staphylococcus aureus bacteraemia in two hospitals in Oxfordshire, 1997-2003: cohort study

Abstract

Objective To determine the incidence of methicillin resistant and methicillin sensitive Staphylococcus aureus (MRSA and MSSA) bacteraemia in inpatients and associated mortality within 30 days after diagnosis. Design Anonymised record linkage study of data from hospital information systems and microbiology databases. Setting Teaching hospital and district general hospital in Oxfordshire. Participants Inpatients aged 18 or over admitted to a teaching hospital between 1 April 1997 and 31 March 2004 and to a district general hospital between 1 April 1999 and 31 March 2004. The main part of the study comprised 216 644 inpatients; patients admitted to haematology, nephrology, or oncology services were not included because most were managed as outpatients. Outcome measures Nosocomial MSSA and MRSA bacteraemia; death in hospital within 30 days after bacteraemia. Results Rates of S aureus bacteraemia rose between 1997 and 2003, and MRSA was responsible for this increase. Overall mortality 30 days after bacteraemia was 29%. The crude odds ratio for death after MRSA bacteraemia compared with MSSA bacteraemia was 1.49 (95% confidence interval 0.99 to 2.26). Conclusion The spread of MRSA has greatly increased the overall number of cases of S aureus bacteraemia and has contributed to short term mortality after S aureus bacteraemia.