Methicillin-resistant Staphylococcus aureus (MRSA) infections can be difficult to treat. We evaluated the rate of clinical failure in appropriately-treated patients and determined risk factors for failure.

We retrospectively studied a cohort of patients with invasive MRSA infections who completed recommended therapy at one hospital over a 7year period.

Two-hundred and fifteen cases were included. Vancomycin monotherapy was given in 73%. Failure rates by infection site were as follows: osteomyelitis 37/81 (46%), epidural abscess five/18 (28%), surgical wound four/15 (27%), pneumonia eight/45 (18%), endocarditis five/32 (16%), bloodstream five/42 (12%), joint one/23 (4%), and meningitis zero/one (0%). In multivariate analysis, only a diagnosis of osteomyelitis was independently associated with relapse (p<0.001).

We found a high rate of treatment failure in an urban population among patients who completed recommended therapy, largely with vancomycin alone. Failure in osteomyelitis was particularly common. High quality comparative studies of antibiotic regimens for MRSA infections, particularly osteomyelitis, are needed.