Infectious and Rare Diseases

Bacterial Susceptibility & Resistance

When a microorganism is isolated from a patient, the microbiology lab will often perform susceptibility testing. There is often confusion about what these results mean and how it can be used by the clinician to guide the treatment of the patient. The goal of antimicrobial susceptibility testing is to predict the in vivo success or failure of antibiotic therapy. Tests are performed in vitro, and measure the growth response of an isolated organism to a particular drug or drugs. The tests are performed under standardized conditions so that the results are reproducible. The test results should be used to guide antibiotic choice. The results of antimicrobial susceptibility testing should be combined with clinical information and experience when selecting the most appropriate antibiotic for your patient.