Abstract

RECOVERY RATE OF MYCOBACTERIUM TUBERCULOSIS BY BACTEC MGIT 960 LIQUID CULTURE SYSTEM FROM SPUTUM SAMPLES OF PRESUMPTIVE PULMONARY TUBERCULOSIS PATIENTS

George Sebastian, S. K. Tripathy, Vishwanatha T.* and P. Kumar

ABSTRACT

Bacteriological investigation of sputum is the best way of diagnosing pulmonary Tuberculosis. The aim of this study was to compare the recovery rate, sensitivity, specificity, predictive value, likelihood ratio, time to detection and contamination rate of MGIT liquid culture system with L J solid culture system from sputum samples of pulmonary TB suspects attending DMC of K.C. General Hospital, Bengaluru. Two additional sputum samples (spot and morning) were collected and transported to National Tuberculosis Institute, Bengaluru laboratory. Sputum’s were processed both in MGIT 960 liquid culture and solid culture following the standard guidelines. The recovery rate of Mycobacterium tuberculosis in both the culture system was analysed. A total of 1,376 sputum samples were processed. The recovery rate of MGIT was 85 % (n=259) and L J was 81 % (n=248) out of total isolated 304 (22%) Mycobacterium tuberculosis bacilli by both combined. The sensitivity of MGIT was 75%, specificity was 93%, positive likelihood ratio was 10.83, negative likelihood ratio was 0.26, positive predictive value was 72% and negative predictive value was 94% taking L J as reference gold standard. The mean time to detection for MGIT was shorter (10 days) in comparison to L J (17 days). MGIT 960 liquid culture system is as efficient as L J solid culture for isolation of TB bacilli and complements it in combination, with reduced time for detection.

Keywords: Bactec MGIT 960, Lowenstein Jensen, Time to Detection, Pulmonary TB