High rate of decreasing daptomycin susceptibility during the treatment of persistent Staphylococcus aureus bacteremia
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Daptomycin is bactericidal against Staphylococcus aureus, with susceptibility defined as a minimal inhibitory concentration (MIC) ≤1 μg/ml. Higher MIC developed in a few cases during therapy. The frequency of MIC rise in persistent bacteremia is unknown. We evaluated all patients with S. aureus bacteremia (SAB) treated with daptomycin (≥2 days) from 1 April 2004 to 30 October 2006. All patients with post-daptomycin-exposure saved isolates were studied. Daptomycin susceptibility was determined (in duplicate) on all pre- and post-daptomycin-exposure isolates by the broth (Mueller-Hinton) microdilution method. Among 74 treatment courses in 67 patients, 18 were for SAB. Ten had persistent bacteremia (median = 11 days; range = 1–21) and post-daptomycin-exposure saved isolates. The patient age was 29–84 years (median = 57.5 years). Intravascular catheter was the most common source (50%). Most patients (90%) failed therapy prior to starting daptomycin. The initial daptomycin dose was 4 mg/kg in four (40%) cases. The pre-exposure MIC was 0.125–0.5 μg/ml. The post-exposure MIC increased in four cases and was elevated in two cases (60%), to 2 μg/ml in five and 4 μg/ml in one. MIC rise was noted within 5–15 days of exposure and persisted up to 247 days after stopping daptomycin. Pulse-field gel electrophoresis (PFGE) band pattern of isolates with increased MIC revealed 1–3-band differences, implying genetic relatedness. All patients with non-susceptible isolates relapsed or failed therapy. These findings illustrate that daptomycin susceptibility often decreases during the treatment of persistent SAB. Therefore, susceptibility should be closely monitored during therapy.
- 2.Clinical and Laboratory Standards Institute (CLSI) (2006) Performance standards for antimicrobial susceptibility testing: 16th information supplement. CLSI document M100–S16, National Committee for Clinical Laboratory Standards (NCCLS), Wayne, PAGoogle Scholar
- 3.Fowler VG Jr, Boucher HW, Corey GR, Abrutyn E, Karchmer AW, Rupp ME, Levine DP, Chambers HF, Tally FP, Vigliani GA, Cabell CH, Link AS, DeMeyer I, Filler SG, Zervos M, Cook P, Parsonnet J, Bernstein JM, Price CS, Forrest GN, Fätkenheuer G, Gareca M, Rehm SJ, Brodt HR, Tice A, Cosgrove SE; S. aureus Endocarditis and Bacteremia Study Group (2006) Daptomycin versus standard therapy for bacteremia and endocarditis caused by Staphylococcus aureus. N Engl J Med 355:653–665PubMedCrossRefGoogle Scholar
- 7.Marty FM, Yeh WW, Wennersten CB, Venkataraman L, Albano E, Alyea EP, Gold HS, Baden LR, Pillai SK (2006) Emergence of a clinical daptomycin-resistant Staphylococcus aureus isolate during treatment of methicillin-resistant Staphylococcus aureus bacteremia and osteomyelitis. J Clin Microbiol 44:595–597PubMedCrossRefGoogle Scholar