The use of DNA probes in the identification of leishmanias: discrimination between isolates of the Leishmania mexicana and L. braziliensis complexes.

Kinetoplast DNA (kDNA), initially characterized by buoyant density, from ten reference isolates of the Leishmania braziliensis and L. mexicana complexes has been radio-actively labelled and used as hybridization probes. Filters containing endonuclease digested, electrophoresed, Southern transferred fragments of kDNA from reference and other isolates sent to us for DNA typing have been tested for kDNA sequence homology. We record a complete lack of sequence homology between kDNA of any isolate of the L. braziliensis complex and kDNA of any isolate of the L. mexicana complex. L. b. braziliensis, L. b. guyanensis and L. b. panamensis have kDNA sequences in common with each other and with a number of test isolates from Brazil, Panama, Venezuela and Peru. L. b. panamensis (1.695 g/ml) can be separated from L. b. braziliensis or L. b. guyanensis (1.691-1.693 g/ml) by differences in buoyant density of kDNA. L. m. mexicana and L. m. pifanoi have kDNA sequences in common with each other but kDNA of L. m. amazonensis has insignificant homology with kDNA of other reference isolates of the L. mexicana complex. We conclude that the kDNAs of species of the L. mexicana complex are sufficiently different from kDNA of species of the L. braziliensis complex to make kDNA sequence homology identification a feasible proposition.