Antibiotic and cytotoxic drug susceptibility assays using resazurin and poising agents

摘要

Growth inhibition assays for both microorganisms and mammalian cells are performed by incubating the microorganisms or cells in a growth medium in the presence of resazurin and a suspected growth inhibiting agent. By observing a color change accompanied by the reduction of resazurin to resorfurin, continued cell viability can be determined. The present invention reduces system errors by inhibiting the autoreduction of resazurin by the growth media by incorporating suitable redox stabilizing agents in the medium. In a preferred embodiment the poising agent is potassium ferrocyanide, ferric salt or ferricinium and the medium is maintained at a potential from about +0.3 volts to about +0.45 volts. A second poising agent can be used to inhibit the reduction of resorfin to dihydroresorfin. Preferred second poising agents are methylene blue, toluidine blue, azure I and gallocyanide in amounts to maintain the potential of the growth medium above -0.1 volts.