Phage typing on an agar plate
Typing by phage typing is based on sensitivity towards infection with bacteriophages (vira) .
Typing phages from a standardized panel are spotted onto a loan of bacteria forming semi-confluent colonies of an agar plate. After incubation, a lytic phage infection will result in plaques. = no bacterial growth. The sensitivity toward the different phages is scored and allocation into types is based on the pattern of phage sensitivity. Note that lysis is graded (confluent and semi-confluent), and this is taken into account when defining the types.