How to interpret an antibiotic susceptibility test

摘要

Antibiotic susceptibility testing (AST) is crucial for treating bacterial infections and choosing the mostappropriate antibiotics. The interpretation rules change, but every physician should be aware of themost important ones. In this article we describe the main phenotypes of the most common bacterialspecies, from wild-types strains to strains having acquired resistance mechanisms. Testing thesusceptibility of a few antibiotics allows for the identification of the resistance mechanisms of Staphy-lococcus aureus to beta-lactams (penicillinase or PLP2a acquisition), macrolides, or aminoglycosides.Although streptococci and enterococci exhibit similarities in their susceptibility and resistance pheno-types, some specificities should be noted. Enterobacterales exhibit more complex mechanisms ofresistance, and a systematic and careful analysis of AST is needed. Sometimes, the differentmechanisms described in this article are found in combination, making the interpretation even moredifficult and showing the importance of a close collaboration between microbiologists and physicians.