Journal of Antimicrobial Chemotherapy (1989) 23, 229-235
© 1989 The British Society for Antimicrobial Chemotherapy
research-article |
In-vitro toxoplasmacidal activity of cationic electron carriers
Department of Microbiology, University of Geneva Medical School C.M.U., 9 av. de Champel, 1211 Geneva 4, Switzerland
Received 14 September 1988; accepted 12 October 1988
Exposing murine macrophages infected th the protozoan parasite Toxoplasma gondii to micromolar concentrations of some cationic electron carriers (dyes), resulted in complete killing of the intracellular parasites at concentrations at which these compounds did not seem toxic for the macrophages. The 50% inhibitory concentrations (with 95% confidence limits) were calculated as 0·26 (0·18–0·37), 1·35 (1–2·25), 0·45 (0·13–1·50), and 1·52 (0·91–2·53) µM for crystal violet, phenazine methosulphate, methylene blue and brilliant cresyl blue, respectively. The effects of these electron carriers did not appear to be the result of an enhancement of the natural antitoxoplasmic activity of the macrophages. None of the tested compounds was active against extracellular Tox. gondii as measured by ability to reinfect murine macrophages; thus, these dyes seem to act primarily on actively metabolizing, intracellular, Tox. gondii. Our data also suggest that the killing effect of the electron carriers was not related to the generation of reactive oxygen intermediates as judged by the inability of scavengers of these intermediates to block the activity against intracellular Tox. gondii. Further studies with related redox compounds would have an interesting chemotherapeutic perspective for treating toxoplasma infections.