Characterization of rpoB mutations in rifampin-resistant clinical isolates of M. tuberculosis.

ABSTRACT

Drug resistant strains of M. tuberculosis pose serious public health problem in Egypt. Inadequate treatment regimens and inefficient laboratory diagnosis of drug-resistant strains are likely major contributors to these problems. Mutations of the rpoB gene associated with rifampin resistance were studied in 25 rifampin resistant clinical strains of Mycobacterium tuberculosis isolated in Egypt. Of the 25 resistant isolates, 17 had a mutation in the 81 bp region of the rpoB gene by single strand conformation polymorphism [SSCP] and DNA sequencing. Only two resistance patterns could be detected by SSCP analysis. Sequence analysis revealed that Ser531AELeu arose most frequently missense mutation [76%] followed by Asp516AE Val [24%]. The sensitivity and specificity of the SSCP result were 100% compared with that of the DNA sequencing. These results suggest that SSCP is an efficient method for predicting rifampin resistance which would reduce the time required for susceptibility testing from 4-8 weeks to few days. It is useful for rapid screening of rifampin resistance in isolates of M. tuberculosis