Preliminary evaluation of one conventional nested and two real-time PCR assays for the detection of Toxoplasma gondii in immunocompromised patients.

Toxoplasma reactivation is a serious complication in patients receiving allogenic stem cell transplantation. Real-time PCR assays allow a rapid diagnosis of toxoplasma infection; however, no comparative data are available on the performance of real-time PCR protocols under routine conditions. Therefore, the aim of this study was to amplify Toxoplasma gondii DNA from routine samples of allogenic stem cell recipients using two real-time PCR assays on a LightCycler, and using conventional nested PCR. Conventional nested PCR revealed T. gondii DNA in 16 samples. Only 12 of the 16 samples yielded a positive result in both real-time PCRs. The accuracy of the conventional PCR results was demonstrated by direct sequencing. Amplification and detection of the amplicon was completed in only 1 h using the real-time PCR assays. Thus, real-time PCR substantially accelerates the detection of T. gondii DNA in the majority of positive specimens; however, conventional nested PCR is required for detection of T. gondii DNA in some samples.