Rapid Toxicity Assessment Research Articles

Rapid toxicity assessment of water-soluble and water-insoluble chemicals using a modified agar plate method

This paper presents a simple, rapid and sensitive technique for determining the chemical toxicity of both water-soluble and -insoluble compounds by using a direct agar diffusion assay. The procedure involves the use of an effective, yet non-toxic, carrier solvent system (DMSO-glycerol, 80:20, w/w) to dissolve the test chemicals and a 30°C incubation temperature to accelerate bacterial growth on the seeded agar plate. Under optimum conditions, test results are obtainable within a 3–4 h time frame instead of the 18–48 h incubation required by conventional agar plate methods. Twenty-nine chemical compounds (15 organics, 10 inorganics, 4 organometallics), representing a wide range of environmental contaminants, have been evaluated for their toxicity by the present procedure. The toxicity of the test chemicals could be easily demonstrated at concentrations as low as 0.1 μg per spot on the agar plate. A linear relationship between the test toxicant concentration (μg/spot) and the diameter (mm) of the clear inhibition zone on the agar plates was also observed. This indicates that the procedure is a convenient and economical tool in quantitative toxicological studies of chemical compounds. The proposed method appears to be suitable for both toxicity screening and structure-activity studies.