[Experiments to replace asparagine in Sauton's medium with organic acids in producing PPD tuberculins]

Studied were some carbonic acids to replace asparagine in Soton's original medium in the production of PPD-tuberculins. Used were the following carbonic acids: (a) dicarboxylic saturated--oxalic, malonic, and amber acid; (b) dicarboxylic unsaturated--maleic and fumaric; and (c) dibasic oxicarbonic acids--malic and tartaric. Each of these acids participated in an equal amount as that of asparagine in replacing it in Soton's medium. Two strains were used in the experiments--AN5 and D4. Tuberculins were obtained through precipitating a filtrated material of cultures killed with trichloracetic acid. The tuberculins produced (bovine and avian PPD types) with the use of the various carbonic acids were tested on sensibilized guinea pigs and chickens parallel to the testing of standard tuberculins. The results obtained with the use of carbonic PPD-tuberculins were almost identical to those obtained with the use of standard PPD-tuberculins. The positive results make it reasonable to believe that some of the carbonic acids mentioned above may well be used in the production of PPD-tuberculins.