MRSA colonization and the risk of MRSA bacteraemia in hospitalized patients with chronic ulcers

A cohort study of patients with chronic ulcers was performed to estimate the risk of methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia in a population colonized with MRSA. During a five-year period (January 1990-May 1995), 911 patients with chronic ulcers (CU), as determined by ICD9-CM code search, were admitted to an acute care hospital. Sixty percent (545/911) of these patients with CU had their CU cultured to detect MRSA and 30% (166/545) of these were colonized with MRSA. Among patients with surveillance cultures, those with MRSA colonization had significantly more days of hospitalization and were also more likely to have a central venous catheter during hospitalization compared with patients without MRSA colonization. MRSA bacteraemia occurred in 4% (36/911) of CU patients during the study period and in 6% (32/545) of cultured CU patients. Among the 545 patients who had surveillance cultures, the risk ratio for MRSA bacteraemia when there was MRSA colonization of their chronic ulcer was 16 (95% CI 6-45). Among patients with MRSA colonization, central venous catheter use was the only significant risk factor for MRSA bacteraemia. In 16 of the 28 patients with MRSA bacteraemia and MRSA colonization, the MRSA colonization was identified more than seven days before the bacteraemia. This cohort study identifies MRSA colonized CU patients in an acute care setting as a high-risk population for MRSA bacteraemia.