[Modified EMJH medium for cultivation of Leptospira interrogans serogroup ballum]

Strains within the Ballum serogroup of spirochete Leptospira show fastidious growth with more exigent nutritional requirements than those of other Leptospira pathogenic strains. The influence of 37 nutritional compounds on the growth of Leptospira interrogans serogroup Ballum was investigated employing the synthetic EMJH medium as the base for the study. Microbial growth was estimated spectrophotometrically and direct counts were performed with a Petroff-Hausser counting chamber. Virulence stability was evaluated by calculating the mean lethal dose in hamsters. Antigenicity stability was evaluated by Western blotting using a specific antiserum. Cell yields commonly obtained in EMJH were triplicated without virulence or antigenicity depletions after culturing in a modified EMJH medium with an increased concentration of Tween 80, and the incorporation of sodium acetate and beef extract. Neither the increased concentration of at least 6 components of EMJH nor the incorporation of a variety of new nutrients stimulated cell yields or the growth rate of the microorganism. The results allow us to make use of an enriched culture medium that promotes high cell yields of this fastidious serogroup most prevalent in humans in Cuba.