The efficacy of atovaquone and sulfadiazine was examined alone or in combination for
the treatment of mice infected with six Brazilian Toxoplasma gondii strains previously
genotyped using the PCR-RFLP assays of the SAG2 gene, in addition to RH strain. Swiss
mice were infected intraperitoneally with 10(2) tachyzoites from each strain of T.
gondii and treated with 6.25, 12.5, 25 and 50 mg/Kg/day of atovaquone or 40, 80, 160
and 320 mg/Kg/day of sulfadiazine. In a second experiment, mice were treated with
the association of previously determined doses of each drug. Treatment started 48
hours post-infection, and lasted 10 days. The susceptibility of T. gondii to atovaquone
and to sulfadiazine was different according to the parasite strain. It was observed
strains that are susceptible to atovaquone, and strains that are resistant to it.
Type I strains were more susceptible to the activity of sulfadiazine and more resistant
to atovaquone. Yet type III strains were susceptible to atovaquone and to sulfadiazine.
Association of atovaquone and sulfadiazine presented a synergic effect in the treatment
of mice infected with RH type I strain and an additive effect in the treatment of
mice infected with one type I strain and with two type III strains.