The Center for Alternatives to Animal Testing is an academic center affiliated with the Division of Toxicological Sciences in the Department of Environmental Health Sciences of the Johns Hopkins University Bloomberg School of Public Health.

 

Johns Hopkins School of Public Health

Abstract for TestSmart--A Humane and Efficient Approach to Screening Information Data Sets (SIDS) Data

Microtox as a Substitute for Acute Fish Toxicity Testing

Mark T.D. Cronin
School of Pharmacy and Chemistry
Liverpool John Moores University

The Microtox test is an in vitro assay that utilizes the inhibition of the bioluminescence of the bacterium Vibrio fischeri as its endpoint. Reduction in light output may be measured after exposure to a toxicant for 5, 15, or 30 minutes. Most studies demonstrate that the 15 minute time period is the most acceptable for use. As such, the Microtox test is considered by many workers to provide a rapid, and relatively inexpensive, assessment of chemical toxicity. Furthermore, it has proved a valuable tool, in combination with semi-permeable membrane devices, to assess toxicity of pollutants within natural waters and sediments. Comparison of Microtox and fish toxicity data is best attempted on a mechanism of toxic action basis. The Microtox test is found to be a good substitute for fish toxicity for chemicals acting by a non-polar narcotic mechanism of action. For other mechanisms of action, notably polar narcosis, and for compounds able to form covalent-bonds with macromolecules through electrophilic reactions, poorer relationships are observed. This suggests Microtox is less suitable as a substitute for fish toxicity for these mechanisms of action. Assessment of the validity of Microtox data as a substitute for fish toxicity testing has tended to utilize literature data bases of toxicity values. The most frequently used data base for fish toxicity is that for toxicity to the fathead minnow. This is a well-standardized procedure performed in a single laboratory [Nendza & Russom (1991) Xenobiotica 21:147-170]. In contrast, the data available for Microtox have been collated from a large number of literature sources and are presented with no consideration for the quality of the data [Kaiser & Palabrica (1991) Water Poll. Res. J. Canada 26:361-431]. Inter-laboratory variation in the Microtox data may contribute to the poor relationships observed with fish toxicity. Other workers have found better relationships between Microtox toxicity and that of other species when the Microtox data have been measured in a single laboratory.