EVALUATION OF MGIT OVER OTHER PHENOTYPIC METHODS FOR THE DETECTION OF PULMONARY AND EXTRAPULMONARY TB AT A TERTIARY CARE CENTRE IN NORTH INDIA

This study compares the performance of Mycobacterium Growth Indicator Tube (MGIT) culture against conventional Lowenstein Jensen (LJ) media and direct AFB smear examination in pulmonary and extra pulmonary tuberculosis specimens for isolation and drug sensitivity testing (DST) using solid (LJ) and liquid (BACTEC-MGIT-320) media at a tertiary care centre in North India A total of 132 consecutive clinical samples were obtained from suspected cases of TB for smear-microscopy and culture on LJ and BACTEC-MGIT-320. Positive cultures underwent DST for streptomycin, isoniazid, rifampicin and ethambutol. A total of 132 specimens were cultured on LJ and the BACTEC-MGIT-320. The mean (range) time to detection was 14.2 (3–40) and 23.2 (8–42) days for MGIT-320 and LJ, respectively 69 (52.3%) were positive with either MGIT or culture of which 45 (65.2%) were smear positive and 24(34.8%) were smear negative. On comparing MGIT and LJ culture, 65 (94.2%) were positive with MGIT-320 whereas 62(89.8%) LJ cultures were positive DST was conducted on both MGIT-320 and LJ media in the 58 concordant culture-positive isolates. Thirty patients were classified as having MDR by at least one of the two methods. Of these 28 were identified by MGIT-320 and 24 by LJ (proportion method).Although liquid culture is more sensitive than solid culture, but there was a high degree of agreement between the two systems. Their combined use resulted in a higher recovery rate and detection of more drug resistance strains than using only one of the two methods. The mean time to detection was shorter with liquid culture and its monitoring can be automated to facilitate dealing with large number of specimens.