Phage‐susceptibility testing of bacterial isolates with the standard double‐layer method:³³ (A) susceptible isolate — productive infection and formation of individual plaques detectable at serially diluted phage lysate — and (B) resistant isolate — single plaques absent and early bacterial lysis present only at high concertation of phages. Liquid culture‐based system: (C) across a gradient of multiplicity of infections (MOIs) against eight bacteria on a single 96‐well plate. There are seven MOIs tested from highest to lowest (left to right). Column eight and nine are phage‐only and bacteria‐only controls. (D) Bacterial growth kinetics in presence of phage at differing MOIs.