Serum Albumin as a Food for Human Tubercle Bacilli.

Before the development of egg mediums, serum was used extensively as a medium in the cultivation of tubercle bacilli. Eastwood in 1907 reported that horse, bovine, dog, and pig serums supported good growth of stock cultures of human and bovine tubercle bacilli and also served well as isolation mediums. Since the introduction of egg mediums there has been little use of serum as a medium in itself or incorporated in other mediums. Crystallized horse-serum albumin has been shown by Boissevain (1940) to contain a growth factor for tubercle bacilli. He found that a liquid synthetic medium, ordinarily supporting growth of only 10-1 milligram, gave rapid and abundant growth of 10milligram of tubercle bacilli (H-37) when 0.1% of horse-serum albumin, recrystallized three times, was added. The growthpromoting effect was destroyed by autoclaving at 115 C for ten minutes. The serum albumin especially enhanced growth in the depth of the medium. In the course of our studies on the cultivation of minute inoculums of tubercle bacilli we found that Dorset's synthetic medium with 0.5% human serum albumin performed as efficiently'as Corper's egg-yolk medium. Because of its physical and nutritive properties, this serum albumin medium should be an excellent plating medium for research in which the estimation of numbers of viable tubercle bacilli is essential.