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Volume 13, Number 3—March 2007

Dispatch

Intermediate Vancomycin Susceptibility in a Community-associated MRSA Clone

Christopher J. Graber*Comments to Author , Margaret K. Wong*, Heather A. Carleton*, Françoise Perdreau-Remington*, Barbara L. Haller*, and Henry F. Chambers*
Author affiliations: *San Francisco General Hospital, University of California, San Francisco, California, USA;

Main Article

Table

Antimicrobial susceptibility profiles of blood isolate from November 2005, blood isolate from February 2006, and lumbar isolate from April 2006*

Antimicrobial drugMIC (μg/mL) and CLSI interpretation
NovemberFebruaryApril
Nafcillin>2 R16 R>2 R
Clindamycin2 I≤0.25 S<0.25 S
Erythromycin4 I>8 R>4 R
Trimethoprim-sulfamethoxazole<0.5/9.5 S≤0.25/5 S<0.5/9.5 S
Tetracycline<1 S≤0.5 S†<1 S
Rifampin<1 S≤0.25 S<1 S
Ciprofloxacin>2 R>4 R>2 R
Levofloxacin>4 RND>4 R
Gentamicin<1 S≤0.5 S2 S
Vancomycin<2 S2 S8 I
4–6 I‡
DaptomycinND1 S
LinezolidND2 S2 S
TigecyclineND0.125 S0.125 S

*CLSI, Clinical and Laboratory Standards Institute; R, resistant; I, intermediately resistant; S, susceptible; ND, not done.
†Susceptibility to doxycycline performed instead of to tetracycline.
‡Confirmatory susceptibility by E-test and growth on vancomycin (6 µg/mL) agar screen plates.
§Interpreted as nonsusceptible by the Centers for Disease Control and Prevention. Formal CLSI breakpoints for daptomycin resistance have not been established.

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