Objective: To evaluate whether vancomycin MIC affects vancomycin treatment failure and mortalities in in patients with MRSA bacteremia.
Methods: We studied all patients with MRSA bacteremia (1st episode only) at Seoul National University Hospital during the period between Jan 2007 and Dec 2007. Vancomycin MIC was determined by Etest® (AB BIODISK, Solna, Sweden) using 0.5 McFarland inoculum on Muller-Hinton agar plate. Hetero-vancomycin -intermediate Staphylococcus aureus (hVISA) was detected by screening method with brain-heart infusion (BHI; BD Diagnostics, Sparks, MD) agar plate containing 4µg/mL vancomycin (BHIV4). Persistent bacteremia, vancomycin treatment failure, was defined as persistence of MRSA in blood for 5-days or more despite vancomycin administration.
Results: Total 91 patients were studied. Vancomycin MIC was 2µg/mL in 9(10%) MRSA isolates, 1.5µg/mL in 55(60%) and 1µg/mL in 27(30%). hVISA screening test was positive in 11(12%) MRSA isolates. Results were shown in Table.
Conclusions: Vancomycin MIC=2µg/mL or hVISA were not associated with vancomycin treatment failure or mortalities in patients with MRSA bacteremia. Table. vancomycin MIC and treatment outcome in 91 patients with MRSA bacteremia.
|Persistent bacteremia||P value||30-day mortality||P value||S. aureus-related mortality||P value|
|≤1 µg/mL||7/27 (25)||0.651||6/27 (22)||0.784||5/27 (19)||0.871|
|1.5 µg/mL||13/55 (24)||15/55 (27)||13/55 (24)|
|2 µg/mL||1/9 (11)||3/9 (33)||2/9 (22)|
|Negative||20/80 (25)||0.240||20/80 (25)||0.472||17/80 (21)||0.701|
|Positive||1/11 (9)||4/11 (36)||3/11 (27)|