A Study of Fluid Thioglycollate Medium for the Sterility Test

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Abstract
The results presented formed the basis for a revision of the formula for "fluid thioglycollate medium" recommended by the Natl. Inst. of Health for the sterility test of biol. products. The formula is: l-cystine, 0.75 gm,; NaCl, 2.5 gm.; anhydrous dextrose 5 gm.; agar 0.75 gm.; water-soluble extract of yeast 5 gm.; pancreatic digest of casein (peptone) 15 gm.; Na thioglycollate 0.5 gm. or thioglycollic acid 0.3 ml.; resazurin 1 ml. of a 0.1 % soln. Resazurin used as an Eh indicator is apparently non-inhibitory in contrast to the slight inhibitory action of methylene blue and its zinc chloride salt. In the presence of pancreatic digest of casein, an excellent peptone, initiation of growth was more rapid than in the presence of an acid hydrolyzate. Addition of a water-soluble extract of yeast is needed to supply certain growth factors. The use of buffer K2HPO4 was contraindicated because of retardation of growth. The opt. pH and NaCl content for a number of bacteria was studied. Clostridium acetobutylicum, 824, was more sensitive to variations in pH than in NaCl content. The presence of l-cystine enables C. chauvoei to grow. Preliminary observations indicate that an incubation temp. of 32[degree] C would be better than 37[degree] C for the growth of contaminants in biol. products.