Bacteria, gene mutation testing

Modifications of the standard battery may be necessary for some classes, e.g., antibiotics which are toxic to bacteria or e.g., for compounds like topoisomerase inhibitors which interfere with the mammalian cell replication system. A selection of additional assays is being proposed, further modifications may be acceptable via discussion in the ICH Maintenance Process. Alternative strategies may consider assays like the in vivo Comet assay (single cell gel electrophoresis measuring DNA strand breaks) or gene mutation tests with transgenic animals or in vivo DNA adduct studies. 

Gene Mutation Test in Bacteria (Ames Test)... 

AU ehgible chemicals under REACH require the conductance of a bacterial reverse mutation (Ames) test (Annex Vll, 8.4.1) (EC 2006). For compounds >10t/a, an additional mammalian in vitro cytogenetic test is required (Aimex VIII, 8.4.2) (EC 2006). For the latter, both the chromosome aberration test and the micronucleus test in vitro are considered acceptable. In the case of a negative result in the mammalian in vitro cytogenetic test and in the in vitro gene mutation test in bacteria, data from an in vitro gene mutation study in mammahan ceUs are required (Annex... 

Bacterial reverse mutation test (Ames test) Bacteria Gene mutations in bacteria B13-14/TG471... 

A test for gene mutation in bacteria Gene Bacterial In vitro... 

Under Guideline S2B, the following standard test battery is recommended (1) a test for gene mutation in bacteria, (2) an in vitro test with cytogenetic evaluation of chromosomal damage with mammalian cells or an in vitro mouse lymphoma thymidine kinase (TK) assay, and (3) an in vivo test for chromosomal damage using rodent hematopoietic cells. 

VDC was genotoxic in a number of test systems it induced chromosome aberrations and sister chromatid exchanges in cultured mammalian cells and DNA damage in mice in vivo gene mutations were observed in vitro for bacteria, yeast, and plant cells after metabolic activation. ... 

When tested in bacteria, toluene did not induce prophage, differential killing or gene mutation. In single studies with Saccharomyces cerevisiae, toluene did not induce either gene conversion or gene mutation (WHO, 1985, secondary description). 

There was no evidence of genotoxicity in the standard genotoxicity test battery bacteria reverse mutation (Ames) tests, forward gene mutations in mammalian (Chinese hamster ovary AS42) cells, or mouse bone marrow MN test... 

The bacterial reverse mutation test (Ames Test) investigates the ability of chemicals and drags to induce reverse (back) mutations in bacteria, which involves base pair substitutions additions and/or deletions (frameshift mutations) of one or a few DNA base pairs. The bacterial strains used in the test system have mutations in genes coding for enzymes required for the biosynthesis of the amino acids histidine (Salmonella typhimurium) and tryptophan (Escherichia coli). If... 

A test for gene mutations in bacteria An in vitro cytogenetic test in mammalian cells or in vitro mouse lymphoma tk assay... 

Picloram was not mutagenic in gene mutation assays in bacteria and yeast, with or without metabolic activation. Using the forward mutation spot test picloram was mutagenic in Stertomyces coelicolor, which is not a widely accepted screen for mutagens. 

Orally administered fluoranthene (400 and 750 mg/kg) did not increase the sister chromatid exchange frequency in mice (Palitti et al. 1986). Gene mutations were not produced in bacteria or yeast in a host-mediated assay in which anthracene, benzo[a]pyrene, chrysene, or fluoranthene were administered to mice by gavage positive results were produced in bacteria in the same test system in which mice were exposed to benz[a]anthracene and injected intraperitoneally with the bacteria (Simmon et al. 1979). Other genotoxicity studies are discussed in Section 2.4. 

The genotoxicity of PCBs has been tested in in vivo and in vitro studies with generally negative results. End points that have been examined in these studies include gene mutations in bacteria and Chinese hamster V79 cells, chromosomal aberrations in human lymphocytes and rat and mouse bone marrow cells and spermatogonia, micronuclei in mouse bone marrow cells, and dominant lethal mutations in rat sperm cells. 

Usually two or three different tests in bacteria and mammalian cells are selected to cover the endpoints of gene mutations, clastogenicity (structural chromosome aberrations), and aneuploidy (numerical chromosome aberrations), taking into account physicochemical properties of substances under consideration (see Chapter 11). 

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