Dr. Gisele Macedo Rodrigues da Cunha (Belo Horizonte / BR), Giulia Caroline Dantas Vieira (Belo Horizonte / BR), Dr. Ricardo Wagner de Almeida Vitor (Belo Horizonte / BR), Dr. Erica Martins Duarte (Belo Horizonte / BR)
Different from strains circulating in Europe and North America, Brazil has a great diversity of recombinant or unusual strains of Toxoplasma gondii (atypical strains), and high genetic variability is observed in this country (de Lima-Bessa et. al., 2021). Low response to treatment in the clinics has also been reported, especially in Brazil. Previous studies, including ours, have shown a different pattern of susceptibility to drugs from Brazilian isolates of T. gondii (Silva et. al., 2017 and 2019; de Lima Bessa et. al., 2023). However, the molecular basis of the reduced susceptibility observed for these strains is not known yet. To amplify the knowledge regarding the susceptibility of different Brazilian strains to the conventional therapy of toxoplasmosis, the objective of this study was to evaluate the effectiveness of the drugs pyrimethamine and sulfadiazine to eight Brazilian human isolates of T. gondii (CTBr11, CTBr14, CTBr15, CTBr18, CTBr21, CTBr22, CTBr26, and CTBr27) in a murine model of acute infection. Infected mice were treated for ten days with different doses of sulfadiazine (SDZ), pyrimethamine (PYR), and a combination of SDZ + PYR. While groups of mice infected with CTBr26 and CTBr27 responded well to all doses SDZ, PYR and SDZ+PYR, mice infected with CTBr11 and CTBr14 responded moderately to PYR, and CTBr15, CTBr18, CTBr21, and CTBr22 showed high mortality even when treated with the highest doses of PYR (50mg/kg/day), SDZ (160 mg/kg/day) and their combination (6.2 mg/kg/day PYR and 20 mg/kg/day SDZ). Interestingly, CTBr11, CTBr14, and CTBr27 share the same genotype 11. Other works of drug susceptibility with strains of the same genotype also showed similar results, suggesting that the variability to treatment could be genotype-dependent and not only to a reduced effect on the drugs.
de Lima Bessa G, et al. 2021. Parasitol Res. 120:3065-3076. doi: 10.1007/s00436-021-07282-w.
de Lima Bessa G, et al. 2023. Sci Rep. 13:7359. doi: 10.1038/s41598-023-34502-3.
Silva LA, et al. 2017. PLoS One. 12:e0170689. doi: 10.1371/journal.pone.0170689.
Silva LA, et al. 2019. Exp Parasitol. 202:7-14. doi: 10.1016/j.exppara.2019.05.001.