Antimicrobial susceptibility testing: a primer for clinicians

Appropriate use of antimicrobials in health care continues to be a challenge. Reliable and reproducible antimicrobial susceptibility testing methods are necessary to provide the clinician with valuable information that can be translated into positive clinical outcomes at the bedside. However, there are nuances with these testing methods that, if unrecognized, could lead to misinterpretation of results and inappropriate antibiotic selection. This primer describes the common antimicrobial susceptibility tests used in the clinical microbiology laboratory and reviews how subtle differences in testing methods and technique can influence reported results. Clinicians who have a thorough understanding of qualitative and quantitative methods, automated susceptibility testing systems, and commonly used screening and confirmatory tests for antibiotic-resistant organisms can strengthen institutional antibiotic stewardship programs and improve patient outcomes.