MCQs on Staining methods in diagnostic microbiology: Medical Microbiology

                   MCQs on Staining methods in diagnostic microbiology

 

1. What is the purpose of a decolorizing agent in the Gram staining process?

a) To make the bacteria more visible under the microscope

b) To stain the bacterial capsules  

c) To differentiate between Gram-positive and Gram-negative bacteria     

d) To enhance flagella visibility

2. Which of the following is the primary stain used in acid-fast staining to identify acid-fast bacteria?
a) Crystal violet
b) Carbol fuchsin red     
c) Malachite green
d) Safranin

3. What is the purpose of negative staining method?
a) To stain the background around the microorganisms      
b) To stain the bacterial cells
c) To stain the capsule structure of the microoragnisms
d) To stain the flagella of the microorganisms

4. Which of the following staining method is commonly used to used to visualize and study bacterial flagella?
a) Acid fast stain method
b) Leifson's Method         
c) Negative staining method
d) Simple staining method

5. What is periodic acid-Schiff (PAS) staining technique?
a) Method used for detecting endospores of the bacteria
b) Method used for detecting the spirochetes

c) Method used for detecting the parasites in blood samples

d) Method used for detecting carbohydrates and glycoproteins in tissues specimens      

6. In the Gram staining process, what is the role of iodine?

a) To decolorize the cells

b) To stain the cells

c) To form a complex with crystal violet    

d) To counterstain the cells

7. In endospore staining, which color do endospores typically appear after staining and counterstaining?
a) Blue

b) Green       
c) Pink

d) Red

8. Which stain is commonly used as a counterstain in the Gram staining process?
a) Crystal violet
b) Iodine
c) Ethanol
d) Safranin     

9. Name the most widely used staining method for the direct microscopic detection of the fungal structures?
a) Acid fast stain
b) Giemsa stain
c) Lactophenol cotton blue
d) Periodic acid-Schiff (PAS) 

10. Hematoxylin and eosin (H&E) staining is commonly used to:
a) Identify acid-fast bacteria
b) Observe bacterial capsules

c) Stain bacterial flagella

d) Stain tissues in histology  

11. What is the primary purpose of simple staining in microbiology?
a) To stain all microorganisms in a uniform color for easier observation   

b) To visualize bacterial capsules
c) To differentiate bacteria based on their shape
d) To identify acid-fast bacteria

12. Which stain is commonly used in fluorescent staining for nucleic acid visualization?

a) Carbol fuchsin 

b) DAPI (4',6-diamidino-2-phenylindole)     

c) Methylene blue  

d) Safranin

13. Which of the following flurochrome staining is commonly used for the identification of microorganisms?

a) Acridine orange      

b) Crystal violet

c) Lactophenol cotton blue

d) Safranin

14. Which of the following is a commonly used stain/dye used for the detection of conjunctivitis pathogen Chlamydia trachomatis?

a) Gram staining

b) Giemsa staining      

c) Negative staining

d) Silver staining

15. Name the type of staining used in differential staining method

a) Gram staining

b) Negative staining

c) Simple staining

d) All of the above

16. Bipolar staining is a common technique used in microbiology that helps to distinguish and characterize the bacteria 

Name group of bacteria that exhibit bipolar staining

a) Acid fast bacteria

b) Gram positive bacteria

c) Gram negative bacteria

d) Spirochetes  

17. What is the primary flourochrome stain used for the identification of Mycobacteria when observing the bacteria using a flourescent (ultraviolet) microscope?

a) Auramine-rhodamine

b) India ink

c) Malachite green

d) Safranin

18. All of the following statements are correct regarding the heat fixation procedure used in staining method, Except?

a) Helps to kill or inactivate microorganisms and stop their metabolic activity 

b) Helps cells to adhere firmly to the slide's surface and prevent them from being washed away during subsequent staining steps and rinsing with staining solutions

c) Helps to denature and stabilize the proteins within the sample and maintain the structural integrity of the cells and their components during the staining process

d) All of the above

19. Which of the following staining method is commonly used for the identification of Tinea nigra (fungi) in skin lesions specimen?

a) Giemsa staining

b) Negative staining

c) Ziehl Neelsen staining

d) Silver nitrate staining


 Answers:
1. c) To differentiate between Gram-positive and Gram-negative bacteria

2. b) Carbol fuchsin red.  Mycobacterium species have waxy cell walls that resist conventional staining, thus method such as Ziehl-Neelsen involve the use of carbol fuchsin and acid-alcohol to stain acid-fast bacteria red/pink.

3. a) To stain the background around the microorganisms. This method creates a contrast between the unstained microorganisms and the stained background, making it easier to observe their shape, size, and other structural details. 

4. b) Leifson's Method. The stain coats and thickens the flagella, making them easier to observe under a microscope. This method involves staining with tannic acid followed by basic fuchsin.

5. d) Method used for detecting carbohydrates and glycoproteins in tissues specimens 

6. c) To form a complex with crystal violet  

7. b) Green 

8. d) Safranin

9. c) Lactophenol cotton blue

10. d) Stain tissues in histology. 

11. a) To stain all microorganisms in a uniform color for easier observation 

12. b) DAPI (4',6-diamidino-2-phenylindole)    

13. a) Acridine orange      

14. b) Giemsa staining   

15. a) Gram staining   

16. c) Gram negative bacteria. Bipolar staining (closed safety pin) technique is often used to highlight structures such as flagella or pili.

17. a) Auramine-rhodamine. Highly sensitive and specific for acid-fast bacteria like mycobacteria, it penetrates the bacterial cells of mycobacteria, the bacteria retains the dye even after washing. 

18. d) All of the above

19. d) Silver nitrate staining