Lab Quiz: Lab 1

Question 1

What are the steps to gram stain?

Answer 1

1. Cover smears with crystal violet solution for 1 minute
2. Wash with tap water until excess stain is removed. Drain off excess water
3. Cover smear with gram’s iodine solution for one minute, then wash and drain
4. Decolorize with 95% alcohol up to 10 seconds and wash with tap water
5. Counterstain with safranin for 30 seconds; wash and dry by blotting with bibulous paper
6. Examine each smear with oil immersion objective

Question 2

What is the most critical step in the gram staining process?

Answer 2

Decolorizing

Question 3

What organisms is acid-fast used for?

Answer 3

Nocardia
Mycobacterium
Cryptosporidium

Question 4

What are positive results of gram stain?

Answer 4

Purple

Question 5

What are negative results of gram stain?

Answer 5

Red

Question 6

What are positive results of acid-fast?

Answer 6

Red

Question 7

What are negative results of acid-fast?

Answer 7

Blue/green

Question 8

What is the new methylene blue stain?

Answer 8

A simple positive stain used for quickly checking for the presence of bacteria, their arrangement, and morphology, but it does not differentiate the cell wall