A comparative study between microscopy and culture in detection of M.tb among smear negative pulmonary and extra pulmonary tuberculosis

Authors : Anjana Gopi, Faiza Samreen, Madhulatha C.K

DOI : 10.18231/2394-5478.2018.0066

Volume : 5

Issue : 3

Year : 0

Page No : 313-317

Introduction: Tuberculosis (TB) is still a leading cause of death in many parts of the world. Adept techniques of rapid detection, isolation, identification and susceptibility testing of Mycobacterium tuberculosis (M.tb) are essential for management. Our aim was to compare the sensitivity and rapidity of smear microscopy, concentration method, rapid slide culture, Lowenstein - Jensen (LJ) culture and MGIT semiautomated culture methods in detection of Mycobacterium tuberculosis among smear negative pulmonary TB and extra pulmonary TB cases and to detect the drug resistance pattern to first line drugs among M.tb isolates.
Materials and Methods: A prospective study was conducted for one year between January 2016 to January 2017 in the Department of Microbiology at a tertiary care hospital. Sputum smear negative pulmonary and extra pulmonary specimens were subjected to direct microscopy by Zeihl-Neelsen and fluorescent staining. Culture was done by Rapid slide culture, Lowenstein-Jensen media (LJ media) and BACTEC MGIT system. Positive isolates were confirmed by appropriate biochemical reactions and rapid immunochromatographic test. Drug susceptibility testing was done for first line drugs.
Results: The sensitivity of direct microscopy was 3% and after concentration it was 4%. Overall culture positivity was 12%. Detection rate by LJ method, rapid slide culture method and MGIT methods was 6%, 4% and 12% respectively. The mean detection time was 22.5 days by MGIT and 31.5 days by conventional LJ method.
Conclusion: This study highlights the importance of culturing suspected smear negative pulmonary and extra pulmonary Tuberculosis cases prior to empirical therapy. Newer automated culture methods aid in earlier detection of cases.

Keywords: Extrapulmonary tuberculosis, MGIT, Mycobacterium tuberculosis, Smear negative tuberculosis.

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