Differentiation of rapidly growing mycobacteria with trimethoprim (Tmp)

Inhibition of Mycobacterium smegmatis, M. vaccae, and M. diernhoferi by Trimethoprim (Tmp) in both liquid and solid media is described. Other mycobacteria were not inhibited by the same concentrations. The selective inhibition of the above strains, particularly M. smegmatis, by Tmp could be used for differentiation of these species from other fast-growing acid-fast bacteria.