Emergence of the USA300 strain of methicillin-resistant Staphylococcus aureus in a burn-trauma unit.

Community-associated methicillin-resistant Staphylococcus aureus (MRSA), particularly USA300, is a major pathogen in the outpatient setting. We suspected that USA300 had been introduced into our burn-trauma unit (BTU) when three burn patients presented with numerous simultaneous abscesses. We did molecular typing on 206 MRSA isolates from all patients on the BTU who had MRSA isolated from either nares cultures or clinical specimens obtained between April 11, 2002 and October 24, 2006. We reviewed medical records for all patients who had USA300 and for 75 control patients. Twenty-five of 206 (12.1%) patients who were colonized (n = 3) or infected (n = 22) with MRSA had USA300. Thirteen patients had abscesses drained surgically and eight had necrotizing fasciitis excised. Seven patients had burns (mean burn size 11.8 +/- 3.4%), of who four (66.7%) acquired numerous simultaneous (3-33) abscesses. Fourteen patients acquired USA300 outside of the BTU, and three acquired this strain on the BTU. Cases were more likely to have been hospitalized or to have had an operation in the 6 months before they were hospitalized than were controls (P = .001 for both). To our knowledge, this is the first study to describe numerous simultaneous MRSA abscesses in burn patients. The MRSA strain USA300 may be introduced onto burn units from the community by patients admitted with skin and soft tissue infections, especially abscesses and necrotizing fasciitis. Burn patients may be at risk for numerous abscesses with USA300, because they have open wounds and their immune systems may be compromised.