You do a Gram stain on the Gram standard culture and all you seeare

red bacteria. What can you conclude?

A. You may have decolorized too long.

B. The culture could contain Staphylococci that are older than

24hours

C. You may have forgotten to add the mordant (iodine)

D. The culture contains Gram-negative bacteria.

E. Answer choices a, b, and c.

The correct answer is E. Answer choices a, b, and c.

Explanation:

There can be many causes for a gram standard culture to appear red like if we use decolorizer for a long time then even the gram-positive cells present in the culture will lose their dye and become decolorized. Then they appear red after counterstaining with safranin.

If a gram-positive culture is older than 24 hours they can appear red because after 24 hours because the peptidoglycan starts degenerating and fails to persist crystal violet it their walls.

Iodine makes complex with crystal violet which is retained by peptidoglycan present in gram-positive cell wall. So when we forgot to add iodine crystal violet will not be retained and cells will appear pink.

Thus, the correct answer is E. Answer choices a, b, and c.