DETECTION OF TOXOPLASMA-GONDII IN VENOUS-BLOOD FROM AIDS PATIENTS BY POLYMERASE CHAIN-REACTION

Detection of Toxoplasma gondii in blood by means of the polymerase cha in reaction (PCR) may facilitate the diagnosis and follow-up of cerebr al toxoplasmosis in patients with AIDS. We evaluated this approach wit h seven patients with tissue culture-proven parasitemia, 14 patients w ith presumptive cerebral toxoplasmosis, and 17 healthy human immunodef iciency virus-positive controls. Each sample of blood was assayed on t hree different occasions by a PCR assay based on detection of the gene encoding the P30 surface protein. A positive PCR diagnosis required p ositivity in at least two of the three PCR tests. None of the controls had a positive PCR diagnosis, but six of the seven patients with para sitemia did. Cerebral toxoplasmosis was confirmed in 13 of the 14 pati ents with a presumptive diagnosis; diagnosis by PCR was positive befor e treatment for 9 of these 13 patients, whereas tissue culture was pos itive for only 1 patient. During treatment, blood samples were taken f rom 14 patients at regular intervals until day 12. PCR diagnosis becam e negative on ethidium-stained gels, but persistent signals were obser ved after hybridization, in some cases, for up to 12 days after initia tion of therapy. PCR on venous blood could thus be a sensitive and non invasive method for the diagnosis of cerebral and disseminated toxopla smosis in AIDS patients and could be a potential tool for monitoring t he effects of treatment.