Ames bacterial reverse mutation assay (OECD 471 )


Ames bacterial reverse mutation assay (OECD 471 )

  • Fully compliant with OECD Guideline 471
  • Available as both a GLP or screening assay
  • Flexible options to meet your requirements

GTX Logo + AMES logoA bacterial reverse mutation test (often simply referred to as an ‘Ames test’) is a core component of safety assessment testing batteries, e.g. ICH S2(R1), performed in amino acid-requiring strains of Salmonella typhimurium or Escherichia coli. Point mutations, involving substitution, addition or deletion of one or a few DNA base pairs, are detected when they cause restoration of the functional capability of the bacteria to synthesize an essential amino acid. Hence, revertant bacteria are able to grow in the absence of the amino acid required by the parent test strain.

This assay uses the traditional bacterial reverse mutation test described in OECD Guideline 471. It is based upon scoring bacterial growth (colonies) on selective agar plates after exposure of the bacterial cells to a test chemical, either by incorporation of the test chemical into the agar plates, or by pre-incubation prior to plating out.


Users can choose either the full set of five strains from the GLP version of the assay, or opt for fewer (typically 2) or more (other strains are available.)

  • S. typhimurium TA98
  • S. typhimurium TA100
  • S. typhimurium TA1535
  • S. typhimurium TA1537
  • E. coli WP2 uvra pKM101

Number of replicates

Users can either adopt the full 3x replicates typically used for GLP, or the number can be reduced or increased if requested.

Test Compound Requirement

This will depend on the number of strains and number of repeats. Some typical options are shown below:

Ames Strain Table

GLP Process

When requesting a GLP study, the sponsor will typically provide test item characterisation, formulation information, and analytical methods for formulation analysis.

A draft study plan is prepared for review by the sponsor, Gentronix, and QA group. Once this is approved and the test items supplied, the study can begin.

If no toxicity or solubility information has been provided, a range-finder test is carried out before the main assay is performed. If formulation analysis is required, this is carried out immediately after dosing.

The sponsor is notified of the results of the study.

A draft report is prepared and reviewed by the sponsor, Gentronix and QA. Once approved, a QA statement is added before the final report is issued.