Dk. Howe et al., DETERMINATION OF GENOTYPES OF TOXOPLASMA-GONDII STRAINS ISOLATED FROMPATIENTS WITH TOXOPLASMOSIS, Journal of clinical microbiology, 35(6), 1997, pp. 1411-1414
To determine the genotypes of Toxoplasma gondii strains associated wit
h human toxoplasmosis, we developed a sensitive approach for typing pa
rasites grown from clinical samples by short-term in vitro culture, A
newly described nested PCR assay was capable of amplifying genomic DNA
from as few as five parasites in the presence of host tissues. Typing
was based on DNA polymorphisms at the SAG2 locus, encoding tachyzoite
surface antigen p22. Restriction fragment length polymorphisms in PCR
-amplified SAG2 products were used to classify strains into one of the
three major lineages of T. gondii. This approach was successfully use
d to determine the genotypes of 68 of 72 samples that had been previou
sly isolated from patients with congenital, cerebral, and disseminated
toxoplasmosis, Type II strains of T. gondii were found in a majority
of the samples, accounting for 55 (81%) of the 68 toxoplasmosis cases,
In contrast, type I and III strains were found in only 7 (10%) and 6
(9%) of the 68 cases, respectively, The results of this study support
the previous finding that type II strains are most often associated wi
th human toxoplasmosis, Nested PCR analysis at the SAG2 locus provides
rapid assignment of T. gondii to a specific genotype that should be u
seful in analyzing a variety of clinical samples.