title: Use of Toxoplasma gondii expressing beta-galactosidase for colorimetric assessment of drug activity in vitro.
abstract: A microtiter assay for drug evaluation has been developed with a strain of Toxoplasma gondii that expresses bacterial beta-galactosidase. By using chlorophenol red-beta-D-galactopyranoside (CPRG) as the substrate for beta-galactosidase, the efficacy of a drug against the parasite can be determined with a colorimetric readout. Drugs known to have activity against T. gondii (specifically, pyrimethamine, sulfadiazine, atovaquone, and clindamycin) were tested, and efficacies were determined by CPRG cleavage. The 50% inhibitory concentrations determined by the CPRG-based colorimetric assay were similar to those determined by the traditional radiolabelled uracil incorporation assay. Since CPRG is nontoxic to the parasite, viable drug-treated parasites can be obtained at the conclusion of the assay for further evaluation if desired. This assay provides a high-throughput and nonradioactive alternative for the identification of anti-T. gondii compounds.
authors.affiliation: Department of Microbiology and Immunology, Stanford University School of Medicine, California 94305-5402, USA.
authors.forename: D C
authors.initials: DC
authors.lastname: McFadden
authors.forename: F
authors.initials: F
authors.lastname: Seeber
authors.forename: J C
authors.initials: JC
authors.lastname: Boothroyd
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003124:Colorimetry; D004795:Enzyme Stability; D006801:Humans; D014122:Toxoplasma / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D014316:Tritium; D014498:Uracil / Q000378:metabolism; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D014316:Tritium; D014498:Uracil; D001616:beta-Galactosidase