COMPARISON OF LIQUID BACTEC MGIT 960 AND SOLID LOWENSTEIN-JENSEN CULTURE FOR DETECTION OF MYCOBACTERIUM TUBERCULOSIS IN CLINICAL SAMPLES AT ANAMBRA STATE, NIGERIA

Abstract

Background: Pulmonary tuberculosis is a major public health problem.  Rapid and accurate detection of Mycobacterium tuberculosis (M.tb) and its drug resistance is fundamental for effective control.

Aim: This study evaluated the diagnostic performance, agreement and drug susceptibility testing (DST) using MGIT 960 compared with LJ culture of 530 clinical samples for detection of Mycobacterium tuberculosis.

Materials and Methods: A cross-sectional study was conducted at NAUTH, GHO and COOUTH in Anambra state. Sputum samples of suspected TB participants were collected and cultured using liquid MGIT-960 and solid LJ media. Drug sensitivity testing of positive Mycobacterium tuberculosis isolates against Streptomycin, Isoniazid, Rifampicin and Ethambutol, was performed. Data was analyzed using Epi-info.

Results: MGIT-960 detected 428/530 (80.7%) positive M.tb, 62 (11.7%) negatives, 36 (6.8%) contaminated, and 4 (0.8%) NTM with detection time 11 (6) days compared to  LJ that detected 411/530 (77.5%) positive M.tb, 92 (17.4%) negatives, 22 (4.2%) contaminated and 5 (0.9%) NTM with detection time 30 (11) days,  456(86.0%)were concordant positive M.tb isolates. Assuming LJ as the gold standard, MGIT 960 showed a sensitivity of 94.6%, specificity of 63.2%, positive predictive value of 90.9%, negative predictive value of 75.3%, and accuracy of 86.0%. DST was performed on 389 culture-positive samples. Concordance of resistance between MGIT and LJ varied by drug, Streptomycin 73.8%, Isoniazid 81.8%, Rifampicin 71.4%, and Ethambutol 71.1%. Total prevalence of MDR-TB 20.8%, Concordance MDR-TB for both method 35.8% and discordant MDR-TB 64.2%, MDR-TB 6.4% by MGIT-960 and 6.9% by LJ while Susceptibility was high for all drugs.

Conclusion: MGIT 960 demonstrated high diagnostic yield for M.tb, and identified additional resistant isolates not detected by solid LJ medium. Combined use of both methods improves accurate diagnosis of TB, drug resistance, reduce contamination and guide effective treatment strategies.