Assessing whether available antibiotics, either alone or in combination, efficiently inhibit or kill infecting strains of bacteria requires in vitro antimicrobial susceptibility testing (AST) to predict clinical patients’ outcomes. The various systems for AST all share the need to assess bacterial death or growth inhibition by defining the viability of bacteria exposed to varying concentrations of antibiotics. Newer AST methods are promising, but none yet measures up to the three dominant automated AST systems. Newer genomic methods are expected to become ever more competitive, particularly with the advance of sequencing technologies and further expansions of the microbial resistome database. Developing and adopting better diagnostic technologies to determine antibiotic susceptibilities will lead to tailoring antibiotic prescriptions to individual patients and specifically targeting the pathogens that are making them ill.