Abstract: The present invention is related with Microbiology and particularly with a nutrient mixture and a procedure for the identification and the early count of Gram-negative organisms. This mixture allows the development of five different colony colors in the organisms to be detected, and the appearance of three colored fluorescent emissions, the appearance of three different colors halos and zones with opaque precipitates surrounding such colonies. Those factors, together with the color changes in the medium, allow a differentiation with a high sensibility and specificity level.