Spent Culture Supernatant of Mycobacterium tuberculosis H37Ra Improves Viability of Aged Cultures of This Strain and Allows Small Inocula To Initiate Growth

Spent culture supernatant from early-stationary-phase Mycobacterium tuberculosis H37Ra cultures increased the viability of bacilli from aged cultures of this strain and allowed small inocula to initiate growth in liquid culture. The resuscitation factor was acid labile and heat stable, with a mass of less than 1,375 Da.