對vancomycin有高MIC 的 MRSA 血流感染，要用Daptomycin治療!

Consider Daptomycin for MRSA With High Vancomycin MICs

NEW YORK (Reuters Health) Dec 05 - Daptomycin is best for methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection when the vancomycin minimum inhibitory concentration (MIC) is high, researchers say.

Dr. Marcus J. Zervos and colleagues with Wayne State University and Henry Ford Hospital in Detroit, Michigan say that while the breakpoint for susceptibility of MRSA to vancomycin is supposedly an MIC of 2 mcg/mL, treatment failure has been reported in bloodstream infections with MICs below this threshold.

The researchers also say their findings support recent guidelines suggesting that doctors consider alternative agents when the isolate has a vancomycin MIC above 1 mcg/mL or when patients are not improving.

But, they point out, the guidelines don't have a lot of data behind them, which is why the team reviewed its own experience in patients hospitalized with a MRSA bloodstream infection and an MIC between 1 and 2 mcg/mL.

As reported online November 21 in Clinical Infectious Diseases, the authors compared 59 daptomycin-treated patients and 118 vancomycin-treated patients.

Rates of treatment failure (a composite of death, microbiologic failure or infection recurrence) were 17% in the daptomycin group and 31% in the vancomycin group, although this difference was not statistically significant (p=0.084).

The benefit was mainly driven by lower mortality with daptomycin vs vancomycin (9% vs 20%; p=0.048).

The results "provide the first clinical comparison of alternative therapy in patients with MRSA BSI (bloodstream infection) with a high vancomycin MIC and confirm that vancomycin-treated patients are at high risk for failure; however, this risk is mitigated by treatment with daptomycin," Dr. Zervos and colleagues conclude.

In an editorial, Drs. Adam Weston and Helen W. Boucher with Tufts University School of Medicine in Boston note that daptomycin is less successful in cases with moderate renal impairment.

That and other safety concerns, along with the cost of the drug, "preclude our recommending daptomycin for all patients with elevated vancomycin MICs," they write.

That said, they conclude, "We hope that future prospective studies will clarify the question of whether every patient with an elevated vancomycin MIC benefits from daptomycin therapy."

Clin Infect Dis 2011.