What's the use of susceptibility testing?

The need for routine antibiotic susceptibility testing is not self-evident. Much infection, particularly that seen in domiciliary practice can be (and is) adequately treated on an empirical basis. Although the collection of susceptibility data for the purposes of monitoring antibiotic resistance trends is a useful by-product of routine testing, this could be effectively carried out by periodic surveys designed for the purpose. Nonetheless, there remain many circumstances in which laboratory testing of antibiotic susceptibility contributes directly to patient care, and some in which it is indispensable. An important additional consideration is that the activities and expertise of the microbiology laboratory can have a powerful influence on antibiotic usage, and hence on the pressures that facilitate the emergence of antimicrobial drug resistance.