Glycopeptide minimum inhibitory concentration creep among meticillin-resistant Staphylococcus aureus from 2006–2011 in China

Abstract Vancomycin minimum inhibitory concentration (MIC) creep has recently been demonstrated by many countries but is rarely reported in China. In this study, a total of 1411 meticillin-resistant Staphylococcus aureus (MRSA) isolates were collected from six hospitals in China during the period 2006–2011 and the MICs of vancomycin, teicoplanin and linezolid were determined by broth microdilution according to Clinical and Laboratory Standards Institute (CLSI) guidelines. MIC 50 and MIC 90 values (MICs required to inhibit the growth of 50% and 90% of organisms, respectively) as well as geometric mean (GM) MICs were calculated for all isolates in each year, and MIC creep for the drugs was evaluated. All of the MRSA isolates were susceptible to vancomycin and linezolid. Overall, the vancomycin GM MIC of MRSA isolates was 0.906, 0.952, 0.956, 0.947, 1.013 and 1.040mg/L, with a significantly increasing trend over the years ( P 1μg/mL) were 26.0%, 23.5%, 21.6%, 27.8%, 30.6% and 42.8% from 2006–2011, respectively, and increased over time ( P P >0.05). In conclusion, a tendency towards decreasing susceptibility to glycopeptides in MRSA has emerged in China.