Volume 13, Number 3—March 2007
Dispatch
Intermediate Vancomycin Susceptibility in a Community-associated MRSA Clone
Christopher J. Graber*
, Margaret K. Wong*, Heather A. Carleton*, Françoise Perdreau-Remington*, Barbara L. Haller*, and Henry F. Chambers*
, Margaret K. Wong*, Heather A. Carleton*, Françoise Perdreau-Remington*, Barbara L. Haller*, and Henry F. Chambers*Table
Antimicrobial susceptibility profiles of blood isolate from November 2005, blood isolate from February 2006, and lumbar isolate from April 2006*
| Antimicrobial drug | MIC (μg/mL) and CLSI interpretation | ||
|---|---|---|---|
| November | February | April | |
| Nafcillin | >2 R | 16 R | >2 R |
| Clindamycin | 2 I | ≤0.25 S | <0.25 S |
| Erythromycin | 4 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 R | ND | >4 R |
| Gentamicin | <1 S | ≤0.5 S | 2 S |
| Vancomycin | <2 S | 2 S | 8 I 4–6 I‡ |
| Daptomycin | ND | 1 S | 2§ |
| Linezolid | ND | 2 S | 2 S |
| Tigecycline | ND | 0.125 S | 0.125 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.
