The Antibiogram: From MIC to Breakpoints

The phenotypic antimicrobial susceptibility testing (AST) of bacteria depends on minimal inhibitory concentration breakpoints issued by international breakpoint committees. These breakpoints affect clinical decision-making by determining whether an antibiotic is reported as susceptible or not. An “interpretative reading” of an antibiogram by clinicians aims to analyze the overall susceptibility pattern, not just the result for an individual antibiotic, and so to predict the likely underlying resistance mechanisms. Clinicians should know these interpretative rules and update their knowledge continuously. The purpose of this work is to guide physicians in reading and understanding antibiogram through an attempt of phenotypic interpretation.