The revealing value of the purified protein antigens designed for the bovine tuberculosis screening registers considerable variations between the different batches of product, even in the case of the same obtaining protocol and of the same operator. In order to limit variations in the potency of the purified protein extract and to improve the expression of immunodominant proteins, different culture protocols have been designed, which, under reproducibility conditions, could reduce the variation limits between batches. The study of the genetic profile identified the AN5 strain used as a virulent Mycobacterium bovis strain belonging to the bovis-caprae lineage. The potency of the purified protein extract was quantified by testing dilutions on guinea pigs. The metabolism modulation of the studied strain, by alternative culture conditions, improved its antigens profile, these being the key compounds for the potency of the tuberculin. [ABSTRACT FROM AUTHOR]