Acid-fast staining is used to identify bacteria such as which genus?

Acid-fast staining is used to identify bacteria such as which genus?

• A. Staphylococcus aureus
• B. Mycobacterium tuberculosis
• C. Escherichia coli
• D. Streptococcus pneumoniae

Answer: (B)

Acid-fast staining is used for organisms with waxy, lipid-rich cell walls containing mycolic acids that trap the primary stain and resist decolorization. This makes these bacteria appear bright red or pink after staining. Mycobacterium tuberculosis is a classic example because its mycolic acid–rich wall retains the stain, helping identify TB organisms in specimens. The other listed bacteria lack this waxy wall and will not retain the acid-fast stain, so they don’t appear acid-fast and are typically identified by other staining methods. In practice, acid-fast stains are a rapid screen for mycobacterial infections like tuberculosis.

Acid-fast staining is used for organisms with waxy, lipid-rich cell walls containing mycolic acids that trap the primary stain and resist decolorization. This makes these bacteria appear bright red or pink after staining. Mycobacterium tuberculosis is a classic example because its mycolic acid–rich wall retains the stain, helping identify TB organisms in specimens. The other listed bacteria lack this waxy wall and will not retain the acid-fast stain, so they don’t appear acid-fast and are typically identified by other staining methods. In practice, acid-fast stains are a rapid screen for mycobacterial infections like tuberculosis.