Evaluation of five liquid culture media for rapid detection of Mycobacterium tuberculosis

The BACTEC MGIT 960 system is currently the most widely used rapid culture system for Mycobacterium tuberculosis. However, its reagents have complex compositions, expensive, and rely on import. This study aimed to develop a self-formulated culture with simple composition, low cost, and performance comparable to or even better than that of the BACTEC MGIT 960 system.

Five experimental media were formulated by supplementing Sauton medium with carrot extract, potato extract, oleic acid, or choline chloride. These were compared against commercial MGIT 960 medium using M. tuberculosis H37Rv suspensions (10^-³-10^-6 mg/mL, triplicate cultures). Time to detection (TTD) and growth index (GI) were monitored automatically using the BACTEC MGIT 960 system.

For medium-high inocula (10^-³-10^-5 mg/mL), carrot- and potato-supplemented Sauton media showed equivalent performance to MGIT 960 (1-day longer TTD, P>0.05; comparable GI values). At low inoculum (10^-6 mg/mL), MGIT 960 failed to detect growth within 42 days, whereas supplemented Sauton medium achieved positivity within 30 days. The carrot extract medium performed best (mean TTD = 20.2 days), followed by oleic acid and oleic acid + choline chloride formulations.

Carrot- and potato-supplemented Sauton medium demonstrated comparable performance to the MGIT 960 system for specimens with medium-to-high bacterial loads. Carrot extract, oleic acid, and choline chloride significantly enhanced the detection rate of low-inoculum, with carrot extract exhibiting the most pronounced growth-promoting effects. This study validates an accessible alternative to expensive imported media, particularly beneficial for resource-limited settings.