Risk factors for acquisition of Methicillin-resistant Staphylococcus aureus among patients from a burn unit in Brazil

Methicillin-resistant Staphylococcus aureus (MRSA) is an important agent of colonization and infection in burn units. In order to identify risk factors for MRSA acquisition in a Brazilian burn unit, we performed two retrospective studies. In the first ("cohort" study), 175 patients who were not colonized with MRSA on admission were followed to assess risk factors for MRSA acquisition. In the second ("case-case-control" study), 143 individuals from the previous study who were negative for both MRSA and Methicillin-susceptible S. aureus (MSSA) on admission were followed. Case-control studies were performed to investigate risk factors for MRSA and MSSA acquisition. MRSA and MSSA were recovered from 75 and 23 patients, respectively. In the "cohort" study, only the number of wound excisions (Odds Ratio [OR]=1.55, 95% Confidence Interval [CI]=1.21-1.98, P=0.001) was associated with MRSA acquisition. In the "case-case-control" study, burns involving head (OR=3.43, 95%CI=1.50-7.81, P=0.003) and the number of wound excisions (OR=1.83, 95%CI=1.27-2.63, P=0.001) were significant risk factors for MRSA. Burns involving perineum were negatively associated with MSSA acquisition (OR=0.16, 95%CI=0.03-0.75, P=0.02). In conclusion, the acquisition of MRSA was related to the site of the burn and to the surgical manipulation of tissues, but not to the use of antimicrobials.