FIG. 3.

Determination of nested-PCR sensitivity (A-C) and line probe assay specificity (D) using DNA extracted from sputum samples. (A) Sputa spiked with different amounts of mycobacteria. M, size markers; NC, negative control. Bands corresponding to 603 and 310 bp are indicated. PCR products from 10³, 10², 10, and 1 M. tuberculosis H37Rv CFU are shown. (B) Different amounts of DNA added to nonspiked sputa processed as for panel A. Shown are PCR products from 1 pg, 100 fg, and 10 fg of M. tuberculosis H37Rv DNA. (C) Different amounts of DNA in distilled water. Shown are PCR products from 1 pg, 100 fg, and 10 fg of M. tuberculosis H37Rv DNA. (D) Results obtained after hybridization of the DIG-labeled PCR products from M. tuberculosis H37Rv-spiked sputa with oligonucleotide probes immobilized on nitrocellulose strips. The 320-bp gyrA fragment of M. tuberculosis H37Rv hybridized only to the WT1 and WT2 probes.