Difficulties in the laboratory diagnosis of congenital toxoplasmosis

The protozoan Toxoplasma gondii is an obligate intracellular parasite that infects humans and a broad spectrum of vertebrate hosts. Of the 15 to 85% of world human population is chronically infected with T.gondii depending on geographical location. The aim of this study was to detect the DNA of T.gondii by using either a two-step PCR method and serological assays to investigate the intrauterine infection in the amniotic fluid and blood of a pregnant woman. Patient was 24 years old and at the 16th weeks of pregnancy. IgM and IgG antibodies against T.gondii were measured by a sensitive chemiluminecent paramagnetic immunoassay system. IgM and IgG ELISA and IFAT IgG were performed by using in house antigens. ELISA immuncapture IgM assay was also performed. PCR: Following the DNA extraction, PCR was performed by using 2 different primer sets. T.gondii IgM, IgG antibodies, IgG avidity and PCR of amniotic fluid were found to be positive at the first trimester of the pregnancy. At the 16th week of pregnancy, T.gondii IgM became negative (ELISA immuncapture IgM negative), while IgG antibodies were positive (IFAT IgG: 1/128; ELISA IgG 1/1024). PCR analysis by using two different primer sets derived form T.gondii B1 gene and performed in two different laboratories gave positive results at expected length. No symptom has been detected in the favor of toxoplasmosis by USG controls of the fetus. Patient gave a birth and no symptoms of toxoplasmosis by physical examination and other methods were detected in the baby. In conclusion, due to possibility of the late onset of T.gondii infection, it is suggested that the baby should be followed for a long term.