C. MULTIPLE CHOICE. Write the letter of the correct answer on the space provided. 1. Which of the following is responsible for the acid-fastness of some organisms? a. Peptidoglycan b. Mycolic acid c. Lipopolysaccharide d. Teichoic acid 2. Which of the following acid-fast staining methods requires steam bathing the organism after addition of carbolfuchsin? a. Ziehl-Neelsen method b. Kinyoun method
Answer (1)
The correct answer is b. Mycolic acid .
Mycolic acids are long fatty acids found in the cell walls of certain bacteria, notably those of the genus Mycobacterium . These acids are responsible for the characteristic "acid-fastness" of these organisms. In acid-fastness, the mycolic acids retain certain stains even after decolorization with acid-alcohol agents, which is a unique property distinguishing these bacteria from others. This trait is particularly relevant in identifying pathogens such as Mycobacterium tuberculosis , the bacterium that causes tuberculosis.
The correct answer is a. Ziehl-Neelsen method .
The Ziehl-Neelsen method is a classic staining technique used to identify acid-fast bacteria. This method requires the use of steam as part of the staining process. The application of carbolfuchsin with steam helps the dye penetrate the waxy cell wall of the bacteria. After the initial staining, the cells are decolorized with an acid-alcohol solution and then counterstained with a dye such as methylene blue. The acid-fast bacteria remain red, while non-acid-fast cells take up the counterstain and appear blue. This method distinguishes itself from the Kinyoun method, which does not use heat but relies on a higher concentration of carbolfuchsin.
