Lack of increase in vancomycin resistance of pediatric methicillin-resistant Staphylococcus aureus Isolates from 2000 to 2007.

We retrospectively studied 306 pediatric methicillin-resistant Staphylococcus aureus isolates collected in 2000/2001, 2003, 2005, and 2007 for possible vancomycin minimum inhibitory concentration (MIC) change over time using Etest, agar dilution, and broth microdilution (MicroScan) methods. Vancomycin MICs did not increase. Inducible clindamycin resistance declined significantly (53%-0%, P < 0.001). Considerably different proportions of isolates with vancomycin MIC = 2 microg/mL were identified by different laboratory methodologies, suggesting the need for caution in their interpretation and in comparing published data. During this period the proportion of USA300 strains increased dramatically.