Which test helps diagnose tuberculosis?

Which test helps diagnose tuberculosis?

• A. Silver stain for fungi
• B. Immunofluorescence for Candida
• C. Acid-fast staining
• D. Gram staining

Answer: (C)

Tuberculosis is diagnosed using acid-fast staining because the Mycobacterium tuberculosis cell wall contains mycolic acids that resist decolorization with acid alcohol. This property lets the organism retain the red dye after decolorization, making acid-fast bacilli visible under the microscope with a Ziehl-Neelsen or auramine-rhodamine stain. A sputum sample that shows acid-fast bacilli provides a rapid, presumptive indication of TB and prompts further confirmation by mycobacterial culture and molecular tests. The other stains target organisms that TB is not caused by or detected with: silver stain for fungi would reveal fungi, immunofluorescence for Candida detects yeasts, and Gram staining is not reliable for Mycobacterium due to the waxy, lipid-rich cell wall that doesn’t stain well with Gram methods.

Tuberculosis is diagnosed using acid-fast staining because the Mycobacterium tuberculosis cell wall contains mycolic acids that resist decolorization with acid alcohol. This property lets the organism retain the red dye after decolorization, making acid-fast bacilli visible under the microscope with a Ziehl-Neelsen or auramine-rhodamine stain. A sputum sample that shows acid-fast bacilli provides a rapid, presumptive indication of TB and prompts further confirmation by mycobacterial culture and molecular tests.

The other stains target organisms that TB is not caused by or detected with: silver stain for fungi would reveal fungi, immunofluorescence for Candida detects yeasts, and Gram staining is not reliable for Mycobacterium due to the waxy, lipid-rich cell wall that doesn’t stain well with Gram methods.