If a Gram stain shows under-decolorization, which remedy is appropriate?

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Multiple Choice

If a Gram stain shows under-decolorization, which remedy is appropriate?

Decolorization timing is what this item tests. If a Gram stain shows under-decolorization, Gram-negative cells haven’t had enough solvent exposure to remove the crystal violet–iodine complex. Extending the contact time with the decolorizer helps dissolve the outer membrane and wash away CV–I from these cells, allowing them to take up the counterstain and appear pink, which correctly separates them from Gram-positive organisms. Be mindful that too long a decolorizer exposure can over-decolorize Gram-positive cells as well, so adjust carefully. Decreasing the decolorizer time would worsen under-decolorization, and adding more stain or washing more between steps doesn’t address the root issue.

Decolorization timing is what this item tests. If a Gram stain shows under-decolorization, Gram-negative cells haven’t had enough solvent exposure to remove the crystal violet–iodine complex. Extending the contact time with the decolorizer helps dissolve the outer membrane and wash away CV–I from these cells, allowing them to take up the counterstain and appear pink, which correctly separates them from Gram-positive organisms. Be mindful that too long a decolorizer exposure can over-decolorize Gram-positive cells as well, so adjust carefully. Decreasing the decolorizer time would worsen under-decolorization, and adding more stain or washing more between steps doesn’t address the root issue.

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