Mortality in patients with meticillin-resistant Staphylococcus aureus bacteraemia, England 2004-2005.

A population-based study was undertaken to determine the short term risk of death in English patients diagnosed with meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia. All patients with an MRSA-positive blood culture taken in 2004 and 2005 in England identified through routine surveillance were matched to the national registry of deaths. The study found an overall case fatality (all-cause) within 7 days of MRSA-positive blood culture diagnosis of 20%, rising to 38% within 30 days. Risk of death was highest on the day subsequent to the blood specimen being drawn (4%). Seven-day case fatality rates in women were 16% higher than for men (odds ratio: 1.16; 95% confidence interval: 1.04-1.29), although no significant difference was discernable by day 30. Risk of death increased with rising age, with 28% (425/1513) of patients aged ≥85 years dying within 7 days and 57% (859/1513) within 30 days. A seasonal pattern in case fatality rates was evident, highest in the winter and lowest in the summer. The age-standardised mortality ratios within the first week were 180 and 225 times as high for men and women, respectively, as for the general population. This declined rapidly after 10 weeks to approximately 9 for both sexes. An estimated 5.53 deaths per 100,000 population followed MRSA bacteraemia in 2004 and 2005, although no inference on causality or attributable mortality could be made through this study. The stable, elevated risk of death observable after 10 weeks compared with that in the general population gave an indication of the background risk of death unrelated to MRSA infection.