FDA is issuing this guidance to provide recommendations to update susceptibility test interpretive criteria (STIC) (also referred to as “breakpoints”) in device labeling for antimicrobial susceptibility test (AST) system devices in response to breakpoint updates posted on the FDA-Recognized Antimicrobial Susceptibility Test Interpretive Criteria website. FDA is issuing this guidance to provide recommendations on the marketing submission content for predetermined change control plans (PCCPs) for new AST system devices, describe an enforcement policy for legacy AST system devices, and clarify the process for incorporating by reference a cleared PCCP or breakpoint change protocol into a new 510(k) submission for an AST system device. FDA has determined that the policy and recommendations described in this guidance are expected to facilitate the timely adoption of updated breakpoints in AST system devices, which helps to ensure device safety and effectiveness.