Question

You performed the gram stain. you are expecting to find purple gram-positive cocci and pink gram-negative bacilli. instead, you observe purple cocci but don't seem to see any bacilli. how could you explain this?

Answer 1

This happens when there is no safranin step in your stain procedure.

Gram Staining is a process of dying and differentiation two large groups of bacteria. It includes

1. Staining with a water-soluble dye (crystal violet),

2. Decolorization- ethyl alcohol or acetone is added to the sample (it decolorizes only the Gram-negative)

3. Counterstaining-using of safranin to stain the sample in red. Since the safranin is lighter than crystal violet, it does not disrupt the purple coloration in Gram-positive cells. Only the Gram-negative will be colored in red.