Podcast
Questions and Answers
What are mycolic acids primarily composed of?
What are mycolic acids primarily composed of?
- Short chain fatty acids
- Carbohydrate polymers
- Protein complexes
- Long chain a-alkyl, -hydroxy fatty acids (correct)
How do mycolic acids influence the pathogenicity of certain microorganisms?
How do mycolic acids influence the pathogenicity of certain microorganisms?
- They promote rapid growth of the bacteria.
- They inhibit replication of bacterial DNA.
- They enhance nutrient absorption through the cell wall.
- They protect bacteria from antibiotics and phagocytosis. (correct)
What is the primary stain used in the acid-fast staining procedure?
What is the primary stain used in the acid-fast staining procedure?
- Crystal violet
- Loeffler's alkaline methylene blue
- Safranin
- Kinyoun's carbolfuchsin (correct)
What color do acid-fast positive organisms appear after the acid-fast staining procedure?
What color do acid-fast positive organisms appear after the acid-fast staining procedure?
What happens to non-acid-fast organisms during the decolorization step of acid-fast staining?
What happens to non-acid-fast organisms during the decolorization step of acid-fast staining?
Which of the following genera includes acid-fast bacteria?
Which of the following genera includes acid-fast bacteria?
What kind of bacteria is characterized by having a cell wall that includes mycolic acids?
What kind of bacteria is characterized by having a cell wall that includes mycolic acids?
Which stain is used as a counterstain in the acid-fast staining process?
Which stain is used as a counterstain in the acid-fast staining process?
Why do acid-fast bacteria exhibit extremely slow growth?
Why do acid-fast bacteria exhibit extremely slow growth?
Which of the following is a disadvantage of the thick cell wall of acid-fast bacteria?
Which of the following is a disadvantage of the thick cell wall of acid-fast bacteria?
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Study Notes
Acid-Fast Stain
- Acid-fast bacteria are gram-positive bacteria that contain up to 60% mycolic acids in their cell walls.
- Mycolic acids are long chain a-alkyl, -hydroxy fatty acids.
- Mycolic acids protect against some antibiotics and phagocytosis by macrophages.
- Mycolic acids make it difficult for nutrients to enter the cell, resulting in slow growth for acid-fast bacteria.
- Acid-fast bacteria resist most stains, including the Gram stain.
- The acid-fast stain differentiates between acid-fast positive and acid-fast negative bacteria.
- The primary stain in the acid-fast stain is Kinyoun's carbolfuchsin, which stains acid-fast positive organisms red.
- Acid-fast positive bacteria retain the red stain after decolorization with acid alcohol.
- Acid-fast negative bacteria are decolorized by acid alcohol and are stained blue by Loeffler's alkaline methylene blue.
- Genera Mycobacterium, Nocardia, and Corynebacterium include pathogens.
- The acid-fast stain helps identify pathogens in clinical samples.
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