Genetic characterization of Toxoplasma gondii revealed highly diverse genotypes for isolates from newborns with congenital toxoplasmosis in southeastern Brazil

Abstract

Recent studies of Toxoplasma gondii isolates from animals in Brazil have revealed high genetic diversity. Many of these isolates are virulent to mice. It is speculated that these isolates may also be virulent to humans. However, there is very limited data regarding T. gondii strains from human infection. Therefore, it is not clear whether there is any association between parasite genotypes and disease phenotypes. In this study, a total of 27 T. gondii strains were isolated from humans with congenital toxoplasmosis in Minas Gerais state, Brazil. The genetic variability was assessed by restricted fragment length polymorphism in 11 loci (SAG1, 5' plus 3' SAG2, alternative [alt.] SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico). Genetic analysis of 24 strains revealed 14 different genotypes, including 7 previously identified from animals and 7 new types. The widespread genotype BrII accounted for 29% (7/24) of the isolates and was the dominant genotype involved in this study. This is the first report of genotyping of T. gondii isolates obtained from blood samples from newborns with congenital toxoplasmosis. Genotypic characterization of these isolates suggests high genetic diversity of T. gondii in this human population in Brazil. Future studies are needed to determine the source of contamination of this human population.

Fig 1

Origin of the T. gondii isolates from newborns in the 12 regions of Minas Gerais state, Brazil. The PCR-RFLP genotypes are indicated by numbers (e.g., #11 for genotype 11). *nd, genotyping not done; **mix, mixed genotype.

Fig 2

NeighborNet phylogenetic network of Toxoplasma gondii isolates from Brazil. TgCTBr1 to TgCTBr27 are T. gondii isolates from newborns from Minas Gerais, Brazil.