Analysis of rifampin disk diffusion and stability in 7H10 agar.

Rifampin was incorporated into Middlebrook 7H10 medium either by adding an aliquot of the antibiotic into melted agar (final concentration 1.0 and 3.0 mug/ml) or by submerging a 5 or 15 mug of rifampin paper disk into 5 ml of melted agar contained in one quadrant of a Felson "X" plate.