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557 Vancomycin minimal inhibitory concentration and outcomes of MRSA bacteremia

Saturday, March 20, 2010
Grand Hall (Hyatt Regency Atlanta)
Hee-Chang Jang, M.D. , Seoul National University, College of Medicine, Seoul, South Korea
Koung Ho Song , Seoul National University, College of Medicine, Seoul, South Korea
Wan Beom Park , Seoul National University, College of Medicine, Seoul, South Korea
Eu Suk Kim, MD , Department of Infectious Diseases, Dongguk University International Hospital, Goyang, South Korea
Hong Bin Kim, MD, PhD , Seoul National University Bundang Hospital, Seongnam, Gyonggi-do, South Korea
Nam Joong Kim , Seoul National University, College of Medicine, Seoul, South Korea
Eui-Chong Kim, MD, PhD , Department of Laboratory Medicine, Seoul National University Hospital, Seoul, South Korea
Myoung-don Oh , Seoul National University, College of Medicine, Seoul, South Korea
Background: There is no conclusion about the relationship between vancomicin minimal inhibitory concentration (MIC)=2µg/mL and the outcomes in patients with MRSA bacteremia.  

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.

Characteristics

Persistent bacteremia
P value
30-day mortality
P value
S. aureus-related mortality
P value
Vancomycin
MIC
≤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)
h-VISA
screening test
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)