The use of a streamlined bacterial mutagenicity assay, the MINISCREEN

Abstract

A streamlined bacterial mutagenicity assay, the MINISCREEN, was developed to enable the rapid screening of a large number of chemical compounds on a purely qualitative basis. Experiments with a series of known carcinogens/mutagens and non-carcinogens/mutagens showed a good correlation with conventional bacterial mutagenicity assays (Ames tests), and the subsequent testing of over 300 candidate agricultural chemicals and over 100 industrial chemicals has proven its value as a screening method.

2-Dodecylcyclobutanone Does Not Induce Mutations in the Salmonella Mutagenicity Test or Intrachromosomal Recombination in Saccharomyces cerevisiae

“…No effect on bacterial viability was observed by examination of the bacterial lawn in the top agar. Results for the negative control (solvent) and positive controls (120 mg per well of MMS, 10 mg per well of 2-NF, or 10 mg per well of 2-AA) were consistent with historical data (2,8,15). The concentration of 1 mg per well of 2-DCB in the Miniscreen assay is the equivalent of the maximum allowed concentration (5 mg per plate) in the standard plate incorporation assay (2,8,15).…”

“…Assay procedure. Due to the expense of 2-DCB (.$12,000 per gram), the microtiter plate-based Miniscreen assay (8,15), which uses 20% of the test compound, cells, solvent, and S9 fraction of the standard plate incorporation assay, was used. In short, 500 ml of top agar (458C), 20 ml of test compound (solvent alone, solvent with 2-DCB, or solvent with positive control compound), 20 ml of overnight culture, and 100 ml of 5% S9 solution (if required) were combined, mixed by vortexing, and dispensed into the well of a microtiter plate that contained 5 ml of minimal agar.…”

“…otide excision repair activity and cell walls that are more permeable to large-molecular-weight compounds to increase their sensitivity to genotoxins (Table 1) (2). The Salmonella strains were exposed to 2-DCB, with and without exogenous metabolic activation, using the microtiter plate-based Miniscreen version of the plate incorporation test (2,8,10,15).…”

The micro‐Ames test: A direct comparison of the performance and sensitivities of the standard and 24‐well plate versions of the bacterial mutation test

“…The 6‐well “Miniscreen” involves an 80% reduction in volume and consequently utilizes 80% less test compound compared with the standard method [Diehl et al, , Flamand et al, ]. The 24‐well test described in this paper is a minor adaptation of a 25‐well version originally described by Brooks [] and Burke et al [] and is referred to as the micro‐Ames or µAmes test here and elsewhere [Escobar et al, ] and uses 95% less material than the conventional Ames test. A slight modification of the 24‐well system involves bioluminescent derivatives of test strains TA98 and TA100 [Côté et al, , Aubrecht et al, , Ackerman et al, ] which facilitates enumeration of revertant colonies.…”

Bacterial mutagenicity assays: Vehicle and positive control results from the standard Ames assay, the 6‐ and 24‐well miniaturized plate incorporation assays and the Ames II™ assay

“…Results from this assay for known direct and metabolically activated positive control chemicals, as well as a number of novel unknown test chemicals, correlated well with results from the standard Ames assay. Brooks [] also reported a good qualitative correlation between the Miniscreen and standard Ames assays using TA98 and TA100 strains for 12 known mutagens/carcinogens and 4 known noncarcinogens/nonmutagens. The 6‐well plate assay was developed as a compromise between the standard 100 mm and the 24‐well plate assays mainly because the larger wells are better suited to the use of the TA1535 and TA1537 strains than the 24‐well assay (because of the low number of revertant colonies in control wells), while still economizing on the amount of test chemical required [Diehl et al, ].…”