Bioensayo de la enterotoxina termoestable de E. Coli

Abstract

The production of thermostable enterotoxin by a strain of E. coli was demostrated by the permeability factor assay in the guinea pig's skin (Cavia cobaya). We injected intradermically 0.1 ml. of suspension of the strain diluted in a buffer  solution of borate, pH 7.5, and after 1 hour we measured the blue spots on the skin, produced by an intravenously injected dye (Coomasie's blue). In the same way, suspension of strains cultured in cysteine supplemented media were tested, as well, as the supernatant of the culture free of cells, and several fractions obtained in the purification of the enterotoxin. The strain suspension, and the supernatant of the culture free of cells, produced blue spots of 6.8 and 0.4 cm of diameter with and intensity of 10 and 3 respectively. The cysteine supplementation of the culture media did not increase the production of enterotoxin. Finally, the bioassay was positive for the fractions obtained in the purification of the enterotoxin.