Evaluation of Mycotube, a modified version of Lowenstein-Jensen (LJ) medium, for efficient recovery of Mycobacterium tuberculosis (MTB)

Timely diagnosis of tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is only achieved for ~58% cases. An improved, accurate, time- and cost-effective method for bacteriological confirmation of MTB is necessary. We evaluated Mycotube, a new variant of Lowenstein-Jensen (LJ) culture medium, by comparing it with Mycobacterium Growth Indicator Tube (MGIT) 960 (gold standard), local LJ, and bioMerieux LJ-T in terms of isolation rate and time-to-growth. Pulmonary and extra-pulmonary samples from treatment-naive suspects (n = 207) were decontaminated by the N-acetyl-L-cysteine-sodium hydroxide method and used to inoculate the four media. Subjective and objective parameters were used for evaluation. Mycotube yielded 140 positive results, compared to 162, 69, and 141 from MGIT, local LJ, and LJ-T, respectively. Of these, 139 (67%) were true-positive results and 1 (0.5%) was false-positive. The mean time-to-growth detection was 17.4 days for Mycotube, compared to 14.5, 28.1, and 16.5 days for MGIT, local LJ, and LJ-T, respectively. The mean time-to-growth for local LJ significantly differed from that for MGIT, but not those for LJ-T and Mycotube. No contamination was observed. Mycotube had a sensitivity of 85.8% and a specificity of 97.8% as compared to MGIT. Mycotube offers good results, comparable with those observed for conventional LJ. It requires only basic laboratory infrastructure. The overall cost of the test should be nearly three times lower than that of MGIT. Mycotube helps with TB diagnosis and generates pure isolates for drug susceptibility testing.