A study of phage based diagnostic technique for tuberculosis.

ABSTRACT

BACKGROUND: Tuberculosis (TB) is a leading infectious disease in India. Diagnosis of TB has always been a problem due to slow rate of growth of Mycobacterium tuberculosis. In this study we have compared the conventional tools for diagnosis of TB with the new Fast Plaque TB TM MATERIAL AND METHODS: Two hundred and twelve clinically suspected cases of TB were enrolled for the study. Three consecutive early morning sputum samples were collected from each patient. Sputum smears were examined after staining with ZN stain and the sputum samples were later subjected to culture and phage assay. RESULTS: It was seen from the study that out of the total 212 cases, 106 were phage positive and 106 were phage negative. Sensitivity of the phage test with respect to AFB smear is 94.34% and specificity of the phage test is 93.88%. A total of 120 specimens grew on LJ media, of which 112 were Mycobacterium tuberculosis, 2 were Mycobacterium Kansasii, 4 were Mycobacterium avium complex and 2 grew Mycobacteriumfortuitum group. Out of these 120 specimens which grew on LJ, 104 were also positive for phage assay. All the 8 Non-Tubercular Mycobacteria were negative by the Fast Plaque Assay. Out of the 92 which were negative on LJ, 2 were positive by phage assay. Sensitivity and specificity of phage assay with respect to growth on LJ was 92.86% and 97.83% respectively. CONCLUSION: The study showed that phage assay is a rapid, reliable and cost effective method in diagnosing pulmonary tuberculosis from clinical samples.