Role Of Microscopy In The Diagnosis Of Infectious Disease

Question 1

Describe the steps of the Gram stain procedure

Answer 1

1. ) Place cells on the slide
2. ) Apply primary stain (crystal violet)
3. ) Mordant grams iodine (to set the dye)
4. ) Decolorizer alcohol and/or acetone
5. ) Counterstain safranin

Gram positive=purple
Gram negative=pink

Question 2

What are 4 main clinical utilities of gram staining?

Answer 2

1. ) Direct examination of clinical material to make an initial diagnosis
2. ) Determine the quality of the specimen
3. ) Suggest an unusual organism or provide early presumptive bacterial identification
4. ) Verify the clinical relevance of the culture

Question 3

How do acid fast stains work?

Answer 3

Acid fat stains bacteria with walls containing long chain fatty acids.
Use heat or detergent to drive stain into cell, once in the cell the stain resists decolonization

Stains mycobacterium, no Arica, cryptosporidium, cyclospora. Mycobacterium is the main one identified

Question 4

What are the steps of the acid fast stain?

Answer 4

1. ) Place cells on the slide
2. ) Place primary stain (carbalfuchsin red)
3. ) Decolorizer (HCl, alcohol)
4. ) Counterstain (methylene blue)

Remains red, everything not stained would look blue

Question 5

Describe features of Silver stains.

Answer 5

Silver impregnated stain for formalin fixed tissue

Demonstrate: Spirochetes (syphillis) and bartonella henselae (cat scratch disease)

Question 6

List the four special stains for FUNGI.

Answer 6

1. ) Gomori methenamine silver (GMS): yeast cells and hyphae, pneumocystis jiroveci
2. ) Periodic acid-Schiff (PAS): yeast cells and hyphae
3. ) Mucicarmine (mucin): cryptococcal capsule
4. ) Lactophenol cotton blue

Question 7

List some common stains for parasites (5)

Answer 7

1. ) Wright Giemsa: used for peripheral blood smear
2. ) Trichrome: stains mature collagen blue
3. ) Modified acid fast
4. ) Iodine
5. ) Wet Mounts