Susceptibility Test Methods: General Considerations

Abstract

Determination of the antimicrobial susceptibilities of significant bacterial isolates is one of the most important functions of the clinical microbiology laboratory. The main objective of susceptibility testing is to predict the likely outcome of treatment with the antimicrobial agents tested. Clinical microbiology laboratories can choose from among several conventional and novel methods for the performance of routine antibacterial susceptibility testing. A laboratory may choose to perform rapid detection of some resistance mechanisms by molecular testing or by rapid phenotypic testing. Breakpoints are the values that determine the categories of susceptibility. The approach to setting breakpoints varies by organization or regulatory body. Antimicrobial resistance is becoming widespread among a variety of clinically significant bacterial species. The advent of more readily available molecular techniques, especially whole‐genome sequencing, opens up the possibility of a major shift in the diagnostic laboratory, from phenotypic susceptibility testing to genotypic prediction of resistance.