Homogeneous restriction fragment length polymorphism analysis of the ribosomal DNA repeating unit in New World Leishmania.

We have studied the Sau 3AI restriction length polymorphisms (RFLP) of the non-transcribed ribosomal spacer of Leishmania isolates from the mexicana and braziliensis complexes, using cloned sequences of Leishmania garnhami and Leishmania braziliensis. The L. garnhami probe produced very complex but conserved patterns in the homologous organisms, and these were shared by all the mexicana complex isolates at intermediate stringency conditions. The small subunit rRNA coding region within the probe also revealed a polymorphic Sau 3AI site exclusive of the braziliensis isolates. The braziliensis probe, containing only spacer sequences, yielded simple and very homogeneous patterns in all braziliensis isolates regardless of their geographical origin. Two main groups are identified in the New World isolates by the RFLP analysis in coincidence with the accepted mexicana and braziliensis complexes.