[Layout proposal for a microtitre plate to be used in routine antimicrobial susceptibility testing of bacteria from infections of dogs and cats].

The determination of minimum inhibitory concentrations by broth microdilution is recommended as method of choice for susceptibility testing of veterinary bacterial pathogens. Accordingly, broth microdilution is used in veterinary routine diagnostic laboratories at a progressive rate. To reduce the costs of susceptibility testing, it is reasonable to develop widely accepted uniform microtitre plate layouts that are produced in large quantities. Such microtitre plate layouts have already been developed and published for the susceptibility testing of pathogens from food-producing animals. However, a microtitre plate layout, especially designed for the testing of bacteria from dogs and cats, should be available, too. The choice of the antimicrobial agents or combinations of antimicrobial agents to be included in a suitable layout should be based on the following criteria: (1) the approval and availability of an antimicrobial agent or combination of agents, (2) known cross-resistances, and (3) availability of approved clinical breakpoints. The latter point is of particular importance for the choice of the numbers of concentrations per antimicrobial agent tested and the range of test concentrations. Taking into account these aspects, a science-based layout proposal for microtitre plates, which are suitable for routine testing of bacteria from dogs and cats, is presented and discussed.