USE OF YEAST KILLER SYSTEM TO IDENTIFY SPECIES OF THE NOCARDIA-ASTEROIDES COMPLEX

We evaluated the ability of the yeast killer system to differentiate m embers belonging to the Nocardia asteroides complex (Nocardia asteroid es, Nocardia farcinica, and Nocardia nova). Nocardia strains were sele cted randomly from clinical isolates. Type strains of each Nocardia sp ecies and recognized killer yeasts,were taken from different collectio ns. A clear area of inhibition surrounding the yeast cells demonstrate d a positive killer effect on Nocardia spp. Two yeast strains, Pichia mrakii (K9) and Pichia lynferdii (K76), showed different killer activi ties against each Nocardia species, The group N. asteroides was identi fied as K9(+) K76(-), the group N. farcinica was identified as K9(-) K 76(-), and the group N. nova was identified as K9(+) K76(+). The three killer identifications correlated with specific taxonomic groups dete rmined by using classical methods. The yeast killer system may be a us eful means for identifying organisms within the N. asteroides complex.