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Questions and Answers

What is the most crucial step in gram staining?

  • Adding safranin
  • Adding crystal violet
  • Applying Gram's iodine
  • Decolorization (correct)
  • Which component of the Gram stain is a dry fixative that strengthens the affinity between the cell wall and the stain?

  • Acetone alcohol (correct)
  • Gram's iodine
  • Safranin
  • Crystal violet
  • What provides rigidity to the cell wall in gram-positive organisms by attracting magnesium and calcium?

  • Peptidoglycan
  • Lipoteichoic acid
  • Muramidase
  • Teichoic acid (correct)
  • Why do Mycoplasma, Ureaplasma, and Acholeplasma usually show a gram-negative reaction despite not having a gram-negative cell wall?

    <p>They do not have a cell wall</p> Signup and view all the answers

    Why are spirals (spirochetes) difficult to stain using gram staining?

    <p>They are naturally gram-negative.</p> Signup and view all the answers

    What is the primary reason Mycobacterium and Nocardia spp. are difficult to perform a gram stain on?

    <p>Their cell wall consists of hydrophobic lipids like mycolic acid.</p> Signup and view all the answers

    Which staining method is typically used for Mycobacterium and Nocardia spp. due to their acid-fast nature?

    <p>Ziehl-Neelsen stain (hot)</p> Signup and view all the answers

    In the context of gram staining, what is the significance of gram variability in gram-positive bacteria?

    <p>It results in some cells appearing as either gram positive or negative.</p> Signup and view all the answers

    What is the purpose of acid-fast staining?

    <p>To target a subset of bacteria with mycolic acids in their cell walls</p> Signup and view all the answers

    Which component is part of the Acid-Fast Stain (FHAM)?

    <p>Acid Alcohol Decolorizer</p> Signup and view all the answers

    What happens to acid-fast bacteria during the decolorization step with Acid Alcohol?

    <p>They turn colorless</p> Signup and view all the answers

    Which bacterium is known as a partially acid-fast organism?

    <p>Nocardia</p> Signup and view all the answers

    In the Ziehl-Neelsen Method, what is the primary stain used?

    <p>Carbol Fuchsin</p> Signup and view all the answers

    What effect does the presence of mycolic acids have on acid-fast bacteria?

    <p>Makes them resistant to decolorization</p> Signup and view all the answers

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