如果不能仅根据生物体的特性预测细菌病原体对抗菌剂的敏感性，则可能需要对分离的生物体进行体外抗菌药物敏感性测试。在病原体属于已记录或可能产生对常用抗菌剂耐药性的细菌种类的情况下，药敏试验尤其必要。多种实验室技术可用于测量细菌对抗菌剂的体外敏感性。 临床和实验室标准协会文件M45——不经常分离或挑剔细菌的抗菌剂稀释和纸片敏感性测试方法描述了标准微量稀释和琼脂纸片扩散方法。它还包括一系列旨在标准化测试性能的程序。描述了当前CLSI推荐方法的性能、应用和局限性。

If a bacterial pathogen's susceptibility to antimicrobial agents cannot be predicted based on the identity of the organism alone, in vitro antimicrobial susceptibility testing of the isolated organism may be indicated. Susceptibility testing is particularly necessary in those situations in which the etiological agent belongs to a bacterial species for which resistance to commonly used antimicrobial agents has been documented, or could arise.A variety of laboratory techniques can be used to measure the in vitro susceptibility of bacteria to antimicrobial agents. Clinical and Laboratory Standards Institute document M45--Methods for Antimicrobial Dilution and Disk Susceptibility Testing of Infrequently Isolated or Fastidious Bacteria describes the standard microdilution and agar disk diffusion methods. It also includes a series of procedures designed to standardize test performance. The performance, applications, and limitations of the current CLSI-recommended methods are described.