Myeloablative conditioning predisposes patients for Toxoplasma gondii reactivation after allogeneic stem cell...

Toxoplasmosis is an often fatal opportunistic infection following allogeneic hematopoietic stem cell transplantation and is largely due to deferred diagnosis. In addition, breakthrough infections occur during prophylaxis with trimethoprim-sulfamethoxazole.

From November 2001 onwards, we routinely monitored all stem cell transplant recipients who were seropositive for Toxoplasma gondii and/or who received a transplant from a donor who was seropositive for T. gondii reactivation by polymerase chain reaction of peripheral blood samples. The aim of this study was to evaluate the incidence of and the risk factors for Toxoplasma reactivation in this population not receiving specific prophylaxis. We also studied the feasibility of a preemptive treatment approach based on this routine monitoring.

We report a toxoplasmosis incidence of 8.7% (18 of 208 patients). Twelve patients (5.8%) had a T. gondii infection at diagnosis; 6 patients (2.9%) had Toxoplasma disease, including cerebral toxoplasmosis (n = 5) and cardiopulmonary toxoplasmosis (n = 1). We identified myeloablative conditioning and conditioning with high-dose total body irradiation (10-12 Gy) as risk factors for T. gondii reactivation, whereas patients with a seropositive donor were less likely to experience reactivation. Patients with T. gondii disease had a significantly higher number of transcripts in blood than did patients with a T. gondii infection. Finally, with a strategy of routine monitoring and preemptive treatment with clindamycin-pyrimethamine, we only had 3 Toxoplasma-related deaths among our patients, which is a much lower rate than that reported in the literature.

Systematic monitoring with polymerase chain reaction is a good means to detect T. gondii reactivation and could reduce T. gondii-related mortality among hematopoietic stem cell transplant recipients.