Risk and outcomes of methicillin-resistant Staphylococcus aureus (MRSA) bacteremia among patients admitted with and without MRSA nares colonization

Abstract

Background: The risk of nosocomial methicillin-sensitive Staphylococcus aureus bacteremia in patients with nasal colonization on admission is 3-fold higher than in patients who are not colonized. Limited data on this question have been reported for methicillin-resistant S aureus (MRSA).

Methods: This is an observational cohort study of patients admitted to a tertiary care medical center from October 1, 2007-September 30, 2013, who underwent active screening for nasal colonization with MRSA.

Results: There were 29,371 patients who underwent screening for nasal MRSA colonization; 3,262 (11%) were colonized with MRSA. There were 32 cases of MRSA bacteremia among colonized patients, for an incidence of 1%. Thirteen cases of bacteremia occurred in non-MRSA-colonized patients, for an incidence of 0.05%. The odds of developing MRSA bacteremia for patients who were nasally colonized with MRSA compared with those who were not colonized were 19.89. There was no difference between colonized and noncolonized subjects with bacteremia in all-cause mortality at 30 days or 1 year.

Conclusions: In a setting with active screening for MRSA, the risk of MRSA bacteremia is 19.89-fold higher among colonized than noncolonized patients.

Keywords: Staphylococcus aureus; bacteremia; carrier state; methicillin-resistant S aureus.