No Evidence of Vancomycin Minimal Inhibitory Concentration Creep or Heteroresistance Identified in Pediatric Staphylococcus aureus Blood Isolates

We evaluated vancomycin minimum inhibitory concentration (MIC) trends by 3 methods (broth microdilution, Etest and Vitek 2) in 208 Staphylococcus aureus blood isolates from 2006 to 2009 and assessed for heteroresistance. Vancomycin MICs did not increase nor was heteroresistance identified. Etest yielded higher MIC results than the other 2 methods. No MIC was >2 µg/mL by any testing method.