Antimicrobial susceptibility testing is an important tool for guiding rational use of antimicrobial agents in clinical settings.Proper use of antimicrobial susceptibility testing results requires clinicians and clinical microbiologists to have the knowledge of antimicrobial susceptibility testing and breakpoints,and have the ability to use pharmacokinetic and pharmacodynamic (PK/PD) principles to optimize antimicrobial therapy regimen.(Chin J Lab Med,2013,36:289-291)