Characterisation of Toxoplasma gondii isolates using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) of the non-coding Toxoplasma gondii (TGR)-gene sequences.

The Toxoplasma gondii (TGR) genes constitute a family of non-coding sequences, three of which have been previously described as possible tools for typing of Toxoplasma gondii isolates. We obtained new isolates of T. gondii from domestic and wild animals, and used these to evaluate the possibility of using TGR gene variants as markers to distinguish among T. gondii isolates from different animals and different geographical sources. Based on the band patterns obtained by restriction fragment length polymorphism (RFLP) analysis of the polymerase chain reaction (PCR) amplified TGR sequences, the T. gondii isolates could be separated into seven groups. Sequencing the amplified products showed that at least 20 TGR sequences not hitherto described had been found, demonstrating that the TGR gene family comprises a large number of different yet highly homologous sequences. Each isolate had its own unique TGR sequence. The TGR gene family therefore seems a promising target for typing individual T. gondii isolates and for studying the genetic distance between two isolates, which can be used for tracing routes of infection.