Application of PCR in diagnosis of Mycobacterium tuberculosis complex

Laboratory diagnosis of tuberculosis is based on direct smear and culture, the latter being especially time - consuming. The aim of this study was to compare three laboratory methods for diagnosis of tuberculosis: direct smear, culture and polymerase chain reaction (PCR).

One hundred clinical specimens were collected from Molla-Hadi-Sabzevari health center in Isfahan, Iran. PCR was based on MT1 and MT2 primers common to all species of Mycobacterium tuberculosis complex (M. tuberculosis, M. africanum, M. microti and M. bovis). Primers amplified a 225 bp PCR product. Also a polymerase chain reaction enzyme linked immunoassay (PCR-ELISA) was employed for some of the clinical specimens. The PCR product was the tag in which anti-digoxigenin antibody was bound in the subsequent ELISA. The PCR product was bound to a streptavidin-coated microtitration plate through a biotinylated capture probe.

Out of 50 individuals in control group, there was no positive result of PCR. In patient group 48 out of 50 were positive PCR. The sensitivity of the culture, the direct Ziel-Nelson smear and the PCR were %88, %82 and %96, respectively.

According the results of this study it is concluded that PCR is more sensitive than culture and direct smear.