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	If a gram positive branching bacillus does not grow on GC selective media can it be assumed that the isolate is not a Nocardia sp. (this question in reference to p.515 MCM 8th.Ed.)? Thanks for your help. Javier Garcia Austin, Texas jvno4@austin.rr.com
	The use of selective media (such as Thayer-Martin, Legionella Selective media and others) is very effective for isolation of Nocardia species from specimens with mixed flora and may provide some evidence that the isolate may be a nocardia species. However, lack of growth on such media should not be used to rule out the nocardia. Original trials asked the question will the selective media help in ioslation, but did not didactically evaluate the growth capability of all strains. Conceivably, some strains may fail to grow and thus selective media should never be used alone. Identification still requires traditional phenotypic characterization (including Wallace's antibiogram differences between the different nocardial species or groups) or newer molecular characterization methods.

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