BACKGROUND: Linezolid resistance in methicillin-resistant METHODS: The in vitro susceptibility of 1032 MRSA clinical isolates to linezolid was detected using commercial VITEK-2 equipment via broth microdilution. MRSA isolates with different minimum inhibitory concentration (MIC) values for linezolid were randomly selected to perform the assay of adaptive laboratory evolution with sub-inhibitory concentrations of linezolid. Polymerase chain reaction assays and sequencing techniques were performed to detect well-known molecular determinants related to linezolid resistance, including the expression of RESULTS: After induction with sequentially increasing concentrations of linezolid, all four MRSA strains (L914, L860, L1096, and L2875) evolved into linezolid-resistant strains over various induction times (480, 384, 288, and 240 h) and universally formed small colony variants. A new mutation in the domain V region of CONCLUSION: Strain-specific evolution of resistance to linezolid among MRSA clinical isolates was firstly identified in this study. MRSA isolates with higher MICs for linezolid evolved more easily into resistant ones, which calls for precise monitoring of linezolid resistance levels in patients receiving treatment for MRSA infections with linezolid.