The following tests must be included for the completed test. Stab lactose-gelatin repeatedly to ensure adequate inoculation, and then rinse loop in beaker of warm water before flaming to avoid splattering. Examine lactose-gelatin medium cultures for gas production and color change from red to yellow, which indicates acid production. Prepare Gram stain of sporulation broth and examine microscopically for spores. Examine tubes of motility-nitrate medium for type of growth along stab line.
Nonmotile organisms produce growth only in and along stab.
Motile organisms usually produce diffuse growth out into the medium, away from the stab. Violet color which develops within 5 min indicates presence of nitrites. If no color develops, add a few grains of powdered zinc metal and let stand a few minutes. A positive test after addition of zinc dust indicates that the organism is incapable of reducing nitrates. Some strains of C .