Trends in sources of meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia: data from the national mandatory surveillance of MRSA bacteraemia in England, 2006-2009.

The national mandatory surveillance system for reporting meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia in England has captured data on the source of reported bacteraemias since 2006. This study analysed episodes of MRSA bacteraemia (N=4404) where a probable source of infection was reported between 2006 and 2009. In 2009, this information was available for one-third of reported episodes of MRSA bacteraemia. Of these, 20% were attributed to intravascular devices and 28% were attributed to skin and soft tissue infection. Sixty-four percent of the patients were male, and urinary tract infection was a significantly more common source of MRSA bacteraemia in males compared with females (12% vs 3%). Detection of bacteraemia within two days of hospital admission does not reliably discriminate between community- and hospital-associated MRSA bacteraemia as community cases are frequently associated with an invasive procedure/device. Between 2006 and 2009, there was a significant decline in the proportion of episodes of MRSA bacteraemia associated with central vascular catheters [incidence rate ratio (IRR) 0.42, 95% confidence interval (CI) 0.29-0.61; P<0.001], peripheral vascular catheters (IRR 0.69, 95% CI 0.48-0.99; P=0.042) and surgical site infection (IRR 0.42, 95% CI 0.25-0.72; P=0.001), and a significant increase in the proportion of episodes of MRSA bacteraemia associated with skin and soft tissue infection (IRR 1.33, 95% CI 1.05-1.69; P=0.017) and attributed to contamination of the specimen (IRR 1.96, 95% CI 1.25-3.06; P=0.003). Since data were not available for all cases, the generalizability of these trends depends on the assumption that records with source data reflect a reasonably random sample of cases in each year. These changes have occurred in the context of a general decline in the rate of MRSA bacteraemia in England since 2006.