Comparison of LJ Medium and BACTEC MGIT 960 Culture System for the Diagnosis of Tuberculosis

Abstract

Introduction: Sputum negative pulmonary Tuberculosis (TB) is a major public health problem. So, the emergence of new techniques for a more precise and rapid microbiological identification of Mycobacterium tuberculosis in clinical samples is of great importance to improve the management of TB. Aim: To determine and compare the sensitivity and turnaround time for Mycobacterium tuberculosis detection by the BACTEC Mycobacteria Growth Indicator Tube (MGIT) 960 system, Lowenstein Jensen (LJ) medium and Ziehl-Neelsen (ZN) staining. Materials and Methods: An Institution based, observational, cross-sectional study was conducted at Rajendra Institute of Medical Sciences (RIMS), Ranchi, Jharkhand, India, from July 2013-March 2016. Sputum, pericardial fluid, pleural fluid, peritoneal fluid, pus and endometrial tissue samples were collected from 80 patients of suspected TB cases. All were Acid-Fast stained by ZN staining method and cultured on solid culture LJ medium and on liquid medium (MGIT). Data was analysed using Statistical Package for the Social Sciences (SPSS) software, Version 20.0 (SPSS Inc, Chicago, IL, USA). Fisher’s-Exact test was used to show association of categorical variables. Non-parametric Mann-Whitney U test was used to show median difference of non-normally distributed continuous variables of two groups. Results: Out of the 80 samples, 41 cases were positive by either of the all methods. The positive specimen for ZN staining, LJ media and MGIT were 21, 29 and 41 cases respectively. The mean Time To Detection (TTD) was shorter for MGIT system than LJ media. Both LJ medium and MGIT 960 detected all cases of sputum smear positive cases and in addition significantly higher number than ZN stain in sputum smear negative cases. MGIT 960 detected significantly higher number of cases of sputum negative cases than LJ Media. The mean TTD was also significantly shorter in case of smear positive cases than the smear negative cases by both the solid and liquid culture mediums. Conclusion: The use of liquid media (MGIT) is more accurate and rapid method for the diagnosis of TB. The combination of more than one method is also highly recommended for rapid detection and early treatment of TB.