Evaluation of the treatment of methicillin-resistant Staphylococcus aureus bacteremia

Bloodstream infections are a leading cause of death in the United States. Methicillin-resistant Staphylococcus aureus (MRSA) encompasses >50% of all S aureus strains in infected hospitalized patients and increases mortality, length of stay and healthcare costs. The objective of this study was to evaluate the treatment of MRSA bacteremia with daptomycin, linezolid and vancomycin.

Patients with MRSA bacteremia between June 2008 and November 2010 were reviewed retrospectively. A microbiology laboratory report identified patients with ≥ 1 positive MRSA blood culture. Patients ≥ 18 years receiving daptomycin, linezolid or vancomycin for ≥ 7 consecutive days were included. Polymicrobial blood cultures and patients treated concomitantly with >1 anti-MRSA agent were excluded.

Of 122 patients included, 53 received daptomycin, 15 received linezolid and 54 received vancomycin. Clinical and microbiologic cure rates were similar between daptomycin, linezolid and vancomycin (58.5% versus 60% versus 61.1%; 93.6% versus 100% versus 90%, respectively). Thirteen patients (daptomycin 4/24 versus linezolid 1/9 versus vancomycin 8/49, P = 0.5960) had recurrence while 12 patients had re-infection (daptomycin 5/42 versus linezolid 0/9 versus vancomycin 7/49, P = 0.4755). Treatment failure occurred in 11 patients treated with daptomycin, 4 with linezolid and 9 with vancomycin (P = 0.662). Compared with daptomycin and vancomycin, linezolid-treated patients had higher mortality (P = 0.0186).

No difference in clinical or microbiologic cure rates was observed between groups. Daptomycin and vancomycin appear equally efficacious for MRSA bacteremia, whereas linezolid therapy was associated with higher mortality.