Isolation and Identification of Mycobacterium tuberculosis with Mixed Growth from Positive MGIT 960 Cultures by Re-Decontamination

Tuberculosis (TB) caused by Mycobacterium tuberculosis has been identified as a remerging infectious disease with public health importance globally. Exploitation of better diagnosis techniques for precise isolation of mycobacteria in clinical specimens is of great importance to improve the diagnosis as part of the global TB control efforts. Contamination of broth cultures of acid-fast bacilli (AFB) by bacterial species other than Mycobacterium species frequently occurs. Many of these contaminated cultures require re-decontamination and re-incubation before the appropriate tests can be performed for identification. This study aimed at the isolation/recovery of M. tuberculosis from contaminated MGIT tubes by making minor modification to the standard protocol and access whether the modification has any impact on recovery rate. Among all confirmed 451 mixed growth positive cultures, 89.57% were culture positive (positive for MTBC), 3.80% were culture negative, 4.65% were culture contaminated and 1.99% were found NTM.