Ames Assay for Mutagenicity

The Ames test is designed to evaluate the potential of a test compound to induce reverse mutations in bacteria.

Ames Test Procedure

  • Typically, four tester strains of Salmonella typhimurium (TA98, TA100, TA1535, and TA1537) and one strain of Escherichia coli (WP2 uvrA) are used in each assay.
    • Others are available, including TA97a, TA102, and WP2 uvrA (pKM101).
  • Each tester strain is incubated for two to three days with several dose levels of the test compound in the presence and absence of metabolic activation (S9).
  • A positive outcome is characterized by a dose-dependent increase in revertant frequency that exceeds strain-specific limits.
Image of TA100 plate dosed with DMSO

Image of TA100 plate dosed with DMSO

When to Perform the Ames Test

  • Screening
  • IND-enabling studies
    • As part of the ICH S2(R1) standard battery (Option 1 or 2)
  • REACH requirements
    • As part of Annex VII testing
  • Impurity assessment
    • Required when an impurity, degradant or process intermediate has been identified as a possible mutagen during in silico analysis as per ICH M7 guideline