FIG. 5.

Electropherograms of automatic DNA sequencing after the amplification of rpoB DNA by PCR and nested PCR which were directly performed with the DNA from sputum sample N3983. The PCR DNA sequencing (upper panel) showed ambiguous results due to nonspecific amplification of rpoB DNA. However, nested PCR DNA sequencing (lower panel) revealed a signature nucleotide at codon 529 (CGA) and a mutation at codon 531 (TTG) in the rpoB DNA of M. tuberculosis. N3983 was confirmed by susceptibility testing and sequence analysis of culture isolate as a rifampin-resistant strain harboring a mutation at Ser₅₃₁ (TCG→TTG).