The performance of tofu-whey as a liquid medium in the propagation of mycobacterium tuberculosis strain H37Rv

ObjectiveTo investigate the performance of “tofu-whey liquid medium” for the propagation of Mycobacterium tuberculosis (MTB) strain H37Rv.MethodTwo hundred micro liters (200 μl) of 1 McFarland standard (1 mg/ml-bacillary suspension) were inoculated into different batches of tofu-whey liquid medium. Each series contained three trials of test (tofu-whey liquid medium) and control media (Middlebrook 7H9 medium). Turbidity was measured within three weeks of inoculation using a nephelometer. The combinations of various tofu-whey liquid culture media were as follows; T1 (tofu-whey + ADC + glycerol + Potassium sulfate + Magnesium citrate + Sodium glutamate); T2 (tofu-whey + ADC + glycerol + Potassium sulfate + Magnesium citrate); T3 (tofu-whey + ADC + glycerol + Potassium sulfate); T4 (tofu-whey + ADC + glycerol); T5 (tofu-whey + ADC); and T6 (tofu-whey only).ResultsIn all test and control liquid culture media, the multiplication of M. tuberculosis was documented under light and fluorescence microscopy. Of various tofu-whey medium used, T1 demonstrated the most potential for MTB propagation. The increased turbidity reading represented by the value in “unit drop of % transmittance” was higher (25 scores) in the T1 tofu-whey medium, compared with the T6 tofu-whey medium (8 scores). The overall growth was significantly better in Middlebrook 7H9 culture media, although by the third day of incubation, the bacillary growth was superior in the T1 tofu-whey culture media. Sub-cultures in Lowenstein–Jensen (L–J) medium yielded between 87% (47 of 54) and 89% (48 of 54) recovery rate with between 7% and 13% contamination rate with coagulase-negative staphylococci.ConclusionTofu-whey media can be used as an economical alternative to Middlebrook 7H9 in resource-limited settings.