Detection of Mycobacterium tuberculosis on stool specimens by PCR among patients with pulmonary tuberculosis

BACKGROUND: To detect Mycobacterium tuberculosis on stool specimens by polymerase chain reaction (PCR) among patients with pulmonary tuberculosis. Detection of M. tuberculosis complex in sputum forms the basis of diagnosis of pulmonary tuberculosis. However, some patients tend to swallow sputum and some are unable to produce sputum. Based on the survival of M. tuberculosis in the gastric fluid, swallowed organisms may be detectable in stool samples. METHODS: The study was carried out on 30 cases each in four groups: sputum smear-positive and sputum smear-negative adults, pediatric patients suspected of pulmonary tuberculosis along with healthy controls. The samples were processed for direct microscopy for acid-fast bacilli (AFB) and M. tuberculosis culture. Stool PCR was done on all 120 samples. RESULTS: AFB was demonstrated in 42 and cultured in 39 out of 240 samples. PCR-targeting IS6110 gene showed positive results in 24 (20%) out of 120 stool samples. PCR in stool showed the highest positivity in sputum smear-positive samples followed by gastric aspirates and sputum smear-negative samples. CONCLUSION: Stool PCR is a potentially useful diagnostic method for pulmonary tuberculosis.