Le ricerche dirette nella diagnosi di Toxoplasmosi. Esperienza di un triennio

Since serologic tests have not proven useful for diagnosis of toxoplasmosis in immunodeficient patiens (patients with hematologic malignancies, bone marrow transplant, solid organ transplant or AIDS) and sometimes in immunocompetent patients (to establish congenital infection in the fetus and newborn and ocular toxoplasmosis) we have used the polymerase chain reaction (PCR) to detect Toxoplasma gondii DNA and tissue cell cultures to isolate the parasite. DNA was amplified using external primers and, in a second step, internal primers, in a nested PCR system. The isolation of parasite was performed on fibroblast cell culture (MRC-5).130 samples were examinated: amniotic fluid (53), cerebrospinal fluid (CSF) (37), blood (32),aqueous fluid (3),biopsy (3),urine (1) and sample from abortion(1). The PCR was performed on all samples and was positive in eight cases: three amniotic fluids, two CSF, two blood and one biopsy. The cell culture was made on 63 samples (53 amniotic fluid and 10 blood) and was positive in two cases of amniotic fluid confirming the PCR results. Because positive predictive value of PCR range from 50 % to 80% this technique should not be used alone for prenatal diagnosis of congenital toxoplasmosis.The positive samples other than amniotic fluid came all from AIDS patients.