Resistance of Bacterial Spores to the Triphenylmethane Dyes

1. Bacterial spores are highly resistant to the bactericidal action of the triphenylmethane dyes. Many Bacillus anthracis and Bacillus subtilis spores resist a saturated aqueous solution of gentian violet for 24 hours at 37 degrees C. They also resist exposure to the same dye solution for 10 minutes at 80 degrees C. 2. The selective bactericidal action of these dyes applies only to the vegetative cells. Spores of the Gram-positive bacteria are more resistant to these dyes than the vegetative cells of Gram-negative bacteria. 3. The vegetative cells of Bacillus anthracis show variation in resistance to the bacteriostatic action of gentian violet. The spores of Bacillus anthracis show variation in resistance to the bactericidal action of gentian violet. 4. Bacillus anthracis can increase in resistance to the bacteriostatic action of gentian violet and grow in dye dilutions inhibiting the original culture. There is the possibility of pathogenic organisms becoming dye-resistant in the body when exposed to non-bactericidal concentrations. For this reason it is advisable to use the greatest concentration of dye compatible with tissue tolerance. 5. Since the spores of pathogenic bacteria may lie dormant for longer periods than the dyes retain their bacteriostatic action in the body frequent applications of the dye should be made in preventing infections by spore-bearing bacteria.