Critical assessment of commercially available microtitre panels for antimicrobial susceptibility testing of veterinary pathogens

Antimicrobial susceptibility testing (AST) in the veterinary sector by broth microdilution is mainly based on commercially available microtitre plates with specific panels. A critical review of commercially available microtitre panels identified AST panels that fulfil the requirements for obtaining reliable AST results by covering the necessary antimicrobial concentrations for both clinical breakpoints as well as quality control (QC) ranges for approved QC strains. However, there are AST panels in which these prerequisites are only in part fulfilled, and some AST panels that do not fulfil the aforementioned criteria at all. Most customers believe that commercially available microtitre panels, which are used in microbiological diagnostic laboratories, reliably allow the identification of susceptible, intermediate or resistant bacteria in addition to sufficient QC ranges to validate the test system. Unfortunately, our findings revealed that this assumption is not always true, and thus it is time to reinforce the necessary requirements that microtitre panels must fulfil to give reliable AST data.