Epidemiology and risk factors for hospital-acquired methicillin-resistant Staphylococcus aureus among burn patients

Methicillin-resistant Staphylococcus aureus (MRSA) is a substantial source of morbidity among burn patients. The objectives of this study were to determine the feasibility and efficacy of surveillance cultures and isolation precautions on limiting the transmission of MRSA among burn patients and to determine risk factors for the development of hospital-acquired MRSA (HA-MRSA). All patients admitted to the burn service from January 2007 to June 2009 were screened by nasal swab culture on admission and weekly thereafter. Other sites were cultured based on clinical suspicion. Patients with MRSA were immediately placed on isolation precautions. Community-acquired MRSA (CA-MRSA) and HA-MRSA were defined as identification of the organism <72 hours from admission (CA-MRSA) or ≥72 hours after admission (HA-MRSA). Charts were retrospectively analyzed to identify risk factors for development of HA. Screening compliance was 100%. Seventy MRSA cases were identified in 752 admissions (9% incidence), including 30 cases of CA-MRSA and 40 cases of HA-MRSA. Over the 30-month study period, HA-MRSA incidence decreased according to a significant linear trend. Independent risk factors for the development of HA-MRSA on multivariate analysis included length of stay >7 days (odds ratio [OR] 12.0, 95% confidence interval [CI] 1.6-91), TBSA affected >10% (OR 6.1, CI 2.6-14.2), age >30 years (OR 4.9, CI 2.0-12.0), and inhalation injury (OR 3.5, CI 1.0-11.7). Surveillance cultures with isolation precautions are practical and effective for preventing HA-MRSA among burn patients. Older patients with prolonged hospital stays, large wounds, and inhalation injury are at greatest risk.