5.3 Synergy tests

Synergy refers to the phenomenon where adding a second agent enhances the activity of the first one. The underlying principle of synergy testing is that the MIC is reduced, or the inhibition zone size increased if the added substance has a synergistic effect – even though the effect might not be large enough to be clinically useful for treatment. This can be done, for example, by modified AST such as commercial combination disk testing (CDT) kits double disk synergy testing (DDT), or using an automated system such as Vitek II^TM, Sensititre^TM or Phoenix^TM.

See Section 9.1.2 for examples of synergy testing.