The concept of combining several histidine-dependent Salmonella strains in a single test, the SIMULTEST, has been applied to the microtitre fluctuation test. The activity of five mutagens was determined in strains TA97, TA98, TA100, and TA102 individually as well as in a SIMULTEST mixture. All five compounds were mutagenic in the SIMULTEST, demonstrating the utility of this time and labour-saving approach of combining strains for testing with this method. The microtitre fluctuation SIMULTEST results were quantitatively comparable to those of the SIMULTEST Salmonella/microsome plate test. The microtitre fluctuation test compared with the plate incorporation assay generally showed more favourable "sensitivity" and "quantity" indices in that four of the five chemicals tested in the fluctuation test were mutagenic at lower doses than in the plate test.

Toluenesulfonhydrazide (TSH) is a high volume production chemical for which there is relatively little toxicological data. In this study, the mutagenic activity of TSH was determined in the Salmonella/mammalian microsome assay and the in vitro chromosomal aberration assay using Chinese hamster ovary cells. TSH induced gene mutations both with and without metabolic activation in the Salmonella/mammalian microsome assay but that it did not induce chromosomal aberrations in Chinese hamster ovary cells. The results of this study indicate that TSH is an in vitro mutagen and should be assessed for in vivo mutagenicity.