Possibility of poor outcomes after treatment using teicoplanin at the minimum inhibitory concentration of ＞2 μg/mL in methicillin-resistant Staphylococcus aureus bacteremia

Only minimal information exists regarding the treatment outcomes of patients suffering from methicillin-resistant Staphylococcus aureus (MRSA) bacteremia treated with teicoplanin (TEIC) when the TEIC minimum inhibitory concentration (MIC) is close to the upper limit of the "susceptibility range" according to the Clinical Laboratory Standards Institute (CLSI). We investigated the outcome of TEIC-treated patients in MRSA bacteremia, focusing on TEIC MIC against MRSA. A retrospective cohort study was conducted on patients with MRSA bacteremia. TEIC treatment failure was defined as any of the following: (1) all-cause 60-day mortality, (2) persistent bacteremia until the end of TEIC treatment, or (3) 30-day recurrence of MRSA bacteremia. Nineteen patients were enrolled, of whom 15 exhibited TEIC MICs ≤2 μg/mL and the remaining 4 exhibited >2 μg/mL. The rate of treatment failure and all-cause 60-day mortality in patients with MIC >2 μg/mL were significantly higher than those in patients with MIC ≤2 μg/mL [4 patients (100%) versus 4 patients (26.7%) (p=0.018) and 4 patients (100%) versus 2 patients (13.3%) (p=0.004), respectively]. Three of four patients (75%) with MIC >2 μg/mL had persistent bacteremia, which was quantitatively higher than in patients with MIC ≤2 μg/mL (1 of 7 patients, 14.3%). Our finding suggests that TEIC MIC >2 μg/mL may be related to poor treatment outcome in MRSA bacteremia, and that TEIC should not be used in this case.