Negative and positive control ranges in the bacterial reverse mutation test: JEMS/BMS collaborative study

Area of Science:

• Genotoxicology
• Microbiology
• Environmental Science

Background:

• The bacterial reverse mutation test (Ames test) is a standard method for assessing mutagenicity.
• Standardized proficiency indicators are crucial for reliable genotoxicity testing across laboratories.

Purpose of the Study:

• To identify and validate proficiency indicators for the bacterial reverse mutation test using a preincubation procedure.
• To establish acceptance criteria for laboratory performance in mutagenicity assays.

Main Methods:

• A multi-laboratory study involving approximately 30 labs from 2013-2016.
• Collection and statistical analysis of negative and positive control data for standard bacterial strains (Salmonella and E. coli) with and without S9 mix.
• Evaluation of dose-response curves for positive control articles.

Main Results:

• The majority of control counts fell within the mean ±2 standard deviation range.
• Negative control counts followed normal or Poisson distributions, while positive control counts were approximately normal.
• Control count distributions remained stable over the four-year study period.
• Dose-response relationships were consistently linear or exponential up to recommended doses.

Conclusions:

• The study provides valuable data for defining acceptance criteria for the bacterial reverse mutation test.
• The findings support the estimation of laboratory proficiency in conducting mutagenicity assays.
• Consistent control data suggests the reliability of the bacterial reverse mutation test when performed under standardized conditions.