Identifying the risk factors for hospital-acquired methicillin-resistant Staphylococcus aureus (MRSA) infection among patients colonized with MRSA on admission.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen in hospital-acquired infections. MRSA-colonized inpatients who may benefit from undergoing decolonization have not been identified.

OBJECTIVE: To identify risk factors for MRSA infection among patients who are colonized with MRSA at hospital admission.

DESIGN: A case-control study.

SETTING: A 146-bed Veterans Affairs hospital.

PARTICIPANTS: Case patients were those patients admitted from January 2003 to August 2011 who were found to be colonized with MRSA on admission and then developed MRSA infection. Control subjects were those patients admitted during the same period who were found to be colonized with MRSA on admission but who did not develop MRSA infection.

METHODS: A retrospective review.

RESULTS: A total of 75 case patients and 150 control subjects were identified. A stay in the intensive care unit (ICU) was the significant risk factor in univariate analysis (P<.001). Prior history of MRSA (P=.03), transfer from a nursing home (P=.002), experiencing respiratory failure (P<.001), and receipt of transfusion (P=.001) remained significant variables in multivariate analysis. Prior history of MRSA colonization or infection (P=.02]), difficulty swallowing (P=.04), presence of an open wound (P=.02), and placement of a central line (P=.02) were identified as risk factors for developing MRSA infection for patients in the ICU. Duration of hospitalization, readmission rate, and mortality rate were significantly higher in case patients than in control subjects (P < .001, .001, and <.001, respectively).

CONCLUSIONS: MRSA-colonized patients admitted to the ICU or admitted from nursing homes have a high risk of developing MRSA infection. These patients may benefit from undergoing decolonization.