A Comparison of the Ames Assay and Mutatox in Assessing the Mutagenic Potential of Contaminated Dredged Sediment

The ability of the Ames assay and of Mutatox to identify the genotoxic potential of dredged sediments was compared. The Ames assay has been used extensively in the testing of environmental contaminants, whereas Mutatox, a new bacterial bioluminescence test, has only recently been used for this purpose. Ten sediments with varying degrees of contamination were soxhlet extracted. Each of the 10 extracts was split with half remaining in a crude form and half cleaned using silica gel chromatography, resulting in 20 extract samples. Both the Ames assay (usingSalmonella typhimuriumstrains TA98 and TA100) and Mutatox were conducted with and without S9 metabolic activation. When metabolically activated, TA98 and TA100 indicated a positive mutagenic response in 80 and 50%, respectively, of the sediment extracts. Without S9 activation, TA98 indicated a positive mutagenic response with half the extracts, whereas only 10% did so with TA100. Mutatox indicated a positive mutagenic response with S9 activation in 75% of the extracts and no mutagenic response in any of the sediment extracts without metabolic activation. In a side-by-side comparison of the Ames assay (TA98 with S9) and Mutatox, 80% of the sediment extracts had similar responses, both positive and negative. Fifty percent of the sediment extracts had similar responses when tested with TA100 and Mutatox in the presence of S9. Mutatox compared reasonably well with the Ames assay but was insensitive to the presence of direct-acting mutagens in the sediments tested. Although Mutatox demonstrates promise as a screening tool to assess sediment genotoxicity, the authors consider it appropriate to use the Ames assay as a confirmation for definitive investigations.