title: Parasiticidal effect of clindamycin on Toxoplasma gondii grown in cultured cells and selection of a drug-resistant mutant.
abstract: Clindamycin, which has been reported to have no significant in vitro activity against Toxoplasma gondii, actually markedly inhibits the growth of this parasite in infected human fibroblasts. When measured 3 days after treatment, the concentration required to reduce parasite growth by 50% is about 1 ng/ml. Some observers failed to note this inhibition because of its markedly delayed onset. At 6 ng/ml, clindamycin is parasiticidal, and the rate and extent of parasite killing increase with higher drug concentrations. With the aid of chemical mutagenesis, we isolated a parasite mutant that is approximately 100-fold more resistant to clindamycin than is the wild type. Lincomycin inhibits T. gondii at a higher 50% inhibitory concentration, about 100 ng/ml. The clindamycin-resistant mutant is partially cross-resistant to lincomycin.
authors.affiliation: Department of Microbiology, Dartmouth Medical School, Hanover, New Hampshire 03755-3842.
authors.forename: E R
authors.initials: ER
authors.lastname: Pfefferkorn
authors.forename: R F
authors.initials: RF
authors.lastname: Nothnagel
authors.forename: S E
authors.initials: SE
authors.lastname: Borotz
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002981:Clindamycin / Q000494:pharmacology*; D004351:Drug Resistance / Q000235:genetics; D008034:Lincomycin / Q000494:pharmacology; D009154:Mutation; D014122:Toxoplasma / Q000187:drug effects* / Q000235:genetics; D014316:Tritium
chemical_list: D014316:Tritium; D002981:Clindamycin; D008034:Lincomycin