The Ames test was developed in the 1970s and takes its name from its creator Bruce N. Ames. The purpose of the Ames test is to determine the mutagenic properties of a chemical. This is done by observing whether mutagenic activity is observed in a bacterial test.
Variations of Ames tests have been developed and can be carried out by contract research organisations such as Gentronix, leading experts in predictive toxicology within the pre-clinical, clinical and regulatory environments, to ensure that test results can be reliably achieved, understood and used to inform further development. Various agar-based test strains offer results comparable to full plate testing formats and study durations of less than three weeks to give cost-effective quality results.
What does it do?
The Ames test can use small quantities of several bacteria strains that carry a specific mutation. The sample’s mutagenic potential is identified by exposing amino-acid-requiring organisms to varying chemical concentrations to determine any reversion event. Media lacking particular amino acids only enable cells undergoing reversion to histidine or tryptophan prototrophy to grow and live. If the sample causes a reversion, it is deemed to be mutagenic.
A positive result indicates that the test chemical can cause DNA mutations and is, therefore, likely to act as a carcinogen. Cancer is often linked to the ability of a cell to mutate. The Ames test provides a speedier and more convenient, and cheaper method of determining some forms of carcinogenic potential than traditional carcinogen assays conducted on mice and rats allow.
The Ames test enables low test item usage to achieve results that help clients determine and demonstrate chemical safety and prepare for regulatory requirements within rapid turnaround times.
Why do we need the Ames test?
Ames tests can detect the mutagenic ability of drugs, cosmetics, pesticides, wastewater and other substances capable of being solubilised into a liquid suspension. The number of colonies within the plate is assessed after incubating at pre-set temperatures for around 72 hours. The mutagenicity of the chemical is then determined by the number of colonies produced compared to the control plate.
The Ames test has revolutionised the speed at which chemicals can be assessed for their risk of mutagenic carcinogenicity in humans at a cost and timeframe that is more in keeping with the modern world, where waiting for animal carcinogenic testing takes many years and is costly.
Bringing new drugs to market has become cheaper and more efficient, leading to faster drug delivery and more readily repeatable testing ability. The Ames test informs early clinical decisions on the viability of future development. It can be used to identify further test requirements and modes of action to complete the investigations and proof required to support regulatory approval applications.
A further range of full plate Ames tests enable lead optimisation through a 2-5 strain Ames test, a crucial part of assessing toxicological hazards within test substances development. Metabolic activation for many Ames tests is through typically induced rat liver S9 and other sources, if appropriate.
Safety for humans
Drugs must be thoroughly tested and achieve safety levels, meaning the effects and mechanisms of action can be predicted when introduced to humans. Levels of cancer-causing chemicals must be identified and understood to conduct a benefit/risk analysis where carcinogenic possibility is identified. No drugs or chemical products can be brought to market without safety testing, and we must support the reduction of animal use in scientific and medical research.
