Stains for the demonstration of spirochetes are based on their property of which?

• A. Argyrophilia
• B. Acid-fastness
• C. Gram positivity
• D. Fluorescence

Answer: (A)

Spirochetes are demonstrated in tissue most reliably because of their argyrophilic nature. Argyrophilia means these organisms have an affinity for silver, so when tissue is treated with silver salts and developed, the spirochetes reduce and deposit metallic silver, appearing as dark, slender threads under light microscopy. This silver-imparted visibility is the basis for classic spirochete stains such as silver impregnation methods.

Acid-fastness would apply to organisms like Mycobacteria, and Gram staining is not a dependable method for visualizing spirochetes in situ. Fluorescence can be used in other contexts (for example with antibodies), but the fundamental property enabling traditional stains of spirochetes is their argentophilic (silver-absorbing) nature.