Comparison of three primer sets for the detection of Mycobacterium tuberculosis in clinical samples by polymerase chain reaction

A number of studies have underlined the interest of the polymerase chain reaction (PCR) in the detection of Mycobacterium tuberculosis in clinical samples. Among the different parameters to be carefully studied the choice of target gene and primers is essential. The amplification of nucleotidic sequences localised on three different target genes (groEL, IS6110, Pab) was examined in 196 clinical samples from patients with suspected tuberculosis or receiving antituberculous therapy. The results obtained after hybridization with non-radioactive labelled probes were compared with the culture data. None of the primer sets studied showed a satisfactory sensitivity (79% to 84%) suitable for it to be used alone. The false-negative specimens with the PCR tests usually corresponded to those that contained few mycobacteria. With the methods described in this study, the use of two or three primer sets located on different target genes allowed to improve the positivity rate compared to the culture and sensitivity of the test (90-98%), particularly for paucibacillary samples. On the other hand, the interpretation was easier when concordant results were obtained.