Which type of bacteria are known to be acid-fast?

Which type of bacteria are known to be acid-fast?

• A. Streptococci
• B. Escherichia coli
• C. Mycobacteria
• D. Salmonella

Answer: (C)

Mycobacteria are known for their acid-fastness, which refers to their ability to retain certain dyes even when exposed to acidic solutions. This characteristic is primarily due to the unique structure of their cell walls, which are rich in mycolic acids and lipids. This lipid-rich content makes the cell wall hydrophobic and prevents the penetration of many staining agents, giving Mycobacteria their distinctive staining properties. The acid-fast stain, commonly known as the Ziehl-Neelsen method, is specifically designed to differentiate Mycobacterium species, such as Mycobacterium tuberculosis, from other bacteria. In the procedure, Mycobacteria appear bright pink against a blue background, indicating their resistance to decolorization by acid alcohol after the initial application of the primary stain, carbol fuchsin. The other bacteria listed do not possess these acid-fast characteristics. Streptococci and Escherichia coli contain more typical bacterial cell wall structures, lacking the high lipid content associated with acid-fast positive organisms. Similarly, while Salmonella has its own distinct features and pathogenicity, it does not exhibit acid-fast properties. Thus, Mycobacteria are uniquely recognized for this trait, making them the correct answer to the question.

Mycobacteria are known for their acid-fastness, which refers to their ability to retain certain dyes even when exposed to acidic solutions. This characteristic is primarily due to the unique structure of their cell walls, which are rich in mycolic acids and lipids. This lipid-rich content makes the cell wall hydrophobic and prevents the penetration of many staining agents, giving Mycobacteria their distinctive staining properties.

The acid-fast stain, commonly known as the Ziehl-Neelsen method, is specifically designed to differentiate Mycobacterium species, such as Mycobacterium tuberculosis, from other bacteria. In the procedure, Mycobacteria appear bright pink against a blue background, indicating their resistance to decolorization by acid alcohol after the initial application of the primary stain, carbol fuchsin.

The other bacteria listed do not possess these acid-fast characteristics. Streptococci and Escherichia coli contain more typical bacterial cell wall structures, lacking the high lipid content associated with acid-fast positive organisms. Similarly, while Salmonella has its own distinct features and pathogenicity, it does not exhibit acid-fast properties. Thus, Mycobacteria are uniquely recognized for this trait, making them the correct answer to the question.