4 Other methods

Activity 6 Types of AST

Timing: Allow about 5 minutes

There are several methods and commercial tests for antimicrobial susceptibility in addition to disk diffusion. List the different types of AST you know about with the names of any commercial examples you are aware of. If you are doing susceptibility testing in your workplace, note which ones are used. If you are not familiar with AST, look at the discussion for this activity now.

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Discussion

Types of AST include:

  • gradient diffusion testing, usually using commercial strips (AB Biodisk Etests, Oxoid MICE, Liofilchem MIC Test Strips)
  • automated systems (such as Vitek, Phoenix or Microscan) or semi-automated systems (Sensititre) that use microdilution methods
  • manual broth dilution methods
  • agar dilution
  • mechanism-specific tests looking for a specific resistance mechanism
  • molecular techniques testing for specific genetic mutations or genes that confer antibiotic resistance.

Mechanism-specific tests and molecular techniques will be covered in the Testing for mechanisms of resistance course, but you will learn more about the other types of test in the next section.

3.3 Measuring and interpreting the test

4.1 Advantages and disadvantages of different types of test in practice