Genotypic detection of Mycobacterium tuberculosis rifampin resistance: comparison of single-strand conformation polymorphism and dideoxy fingerprinting.

Detection of mutations in the rpoB gene of Mycobacterium tuberculosis can be used as an accurate predictor of rifampin resistance in the majority of strains tested. Simple but highly accurate screening methods must be developed for the detection of these mutations. Either DNA sequence analysis or single-strand conformation polymorphism (SSCP) screening can be used to detect rpoB mutations, but these techniques either are expensive or yield results that may prove difficult to interpret when used in a clinical setting. This report describes the use of dideoxy fingerprinting (ddF) as a postamplification screening method to identify rifampin-resistant genotypes. The ddF protocol was performed on the amplified rpoB fragment with no preparatory steps, thus making ddF practical for laboratories equipped for polyacrylamide gel electrophoresis. When compared with the results of SSCP analysis, ddF results were more easily interpreted and contained more sequence-dependent information that facilitated differentiation of functionally significant and silent mutations. The ddF method was used for genotypic determination of rifampin susceptibility of 20 multidrug-resistant strains of M. tuberculosis. The results of this analysis were concordant with DNA sequence analysis and conventional clinical laboratory methods.