Albert Staining 50 FAQs and 30 MCQs
Master Albert staining, the gold-standard technique for detecting Corynebacterium diphtheriae and its characteristic metachromatic granules. This definitive guide covers:
✓ Dual-Component Chemistry:
- Albert’s I (Toluidine Blue + Malachite Green): Stains granules reddish-purple
- Albert’s II (Iodine Solution): Enhances contrast and fixes the stain
✓ Clinical Applications:
- Diagnosis of pharyngeal diphtheria
- Screening during diphtheria outbreaks
- Differentiation from non-toxigenic diphtheroids
✓ Step-by-Step Protocol:
- Optimal smear preparation from throat swabs
- Precise timing for each staining step
- Common errors and troubleshooting
✓ Microscopy Interpretation:
- Positive result: Blue-green bacilli with red-brown polar granules (Babes-Ernst bodies)
- Comparison with Loeffler’s methylene blue and Gram stain results
Essential for:
- Clinical microbiologists
- Public health laboratory staff
- Medical students preparing for exams
Test your expertise with 80+ Albert staining FAQs and MCQs covering:
◼️ Biochemical basis of metachromatic staining
◼️ WHO guidelines for diphtheria reporting
◼️ Differentiation of C. diphtheriae from similar organisms
◼️ Quality control measures in staining
Ideal for:
- Medical microbiology board exams (USMLE, FRCPath)
- Laboratory technician certification
- Public health outbreak investigation training
Albert Staining 50 FAQs
What is Albert staining?
A differential staining technique used to identify metachromatic granules in bacteria like Corynebacterium diphtheriae.
What are metachromatic granules?
Intracellular storage bodies containing polyphosphate, found in certain bacteria.
Which bacteria are identified using Albert staining?
Primarily Corynebacterium diphtheriae, but also Yersinia pestis and some Mycobacterium species.
Why is Albert staining important?
Helps diagnose diphtheria by distinguishing pathogenic C. diphtheriae from nonpathogenic diphtheroids.
What is another name for metachromatic granules?
Volutin granules or Babes-Ernst granules.
How does Albert staining differ from Gram staining?
Gram staining differentiates bacteria based on cell wall composition, while Albert staining targets granules.
What is the principle behind Albert staining?
Acidic granules bind toluidine blue, appearing bluish-black, while cytoplasm stains green.
What is the role of iodine in Albert staining?
Acts as a mordant, enhancing granule staining.
What is the pH of Albert stain?
Adjusted to 2.8 using acetic acid.
What are alternative stains for metachromatic granules?
Neisser’s stain and Pugh’s stain.
What are the two solutions in Albert staining?
Albert Solution 1 (toluidine blue, malachite green, acetic acid, alcohol) and Albert Solution 2 (iodine + KI).
What is the function of toluidine blue in Albert stain?
Stains metachromatic granules bluish-black.
Why is malachite green used in Albert stain?
Counterstains the cytoplasm green.
How is Albert Solution 1 prepared?
Mix toluidine blue (0.15g), malachite green (0.2g), glacial acetic acid (1mL), alcohol (2mL), and water (100mL).
How is Albert Solution 2 prepared?
Dissolve iodine (2g) and potassium iodide (3g) in water (300mL).
Why is acetic acid used in Albert stain?
Lowers pH to enhance selective staining of acidic granules.
Can Albert stain be stored?
Yes, in a tightly closed container away from light at 15-30°C.
What happens if Albert stain is exposed to light?
Iodine may degrade, reducing staining efficiency.
What is the shelf life of Albert stain?
As per manufacturer’s expiry date (typically months to a year).
Can expired Albert stain be used?
No, it may give false-negative results.
How is a smear prepared for Albert staining?
A thin bacterial smear is made, air-dried, and heat-fixed.
Why is heat fixation important?
Kills bacteria and adheres them to the slide.
How long is Albert Solution 1 applied?
3-7 minutes (varies by protocol).
Should the slide be washed after Albert Solution 1?
No, excess stain is drained but not washed.
How long is iodine (Albert Solution 2) applied?
1-2 minutes.
Why is the slide not washed after Solution 1 but washed after Solution 2?
To prevent washing away the initial stain before mordanting.
What happens if the staining time is too short?
Granules may not be clearly visible.
What happens if the staining time is too long?
Over-staining may obscure granules.
Should blotting paper be used after staining?
Yes, to gently dry the slide.
What magnification is used to observe results?
1000x (oil immersion).
What color are metachromatic granules after staining?
Bluish-black or purple-black.
What color is the bacterial cytoplasm?
Light green.
How are C. diphtheriae cells arranged?
In “L,” “V,” or Chinese letter-like patterns.
What does a negative Albert stain indicate?
Absence of metachromatic granules (possibly nonpathogenic diphtheroids).
Can other bacteria show metachromatic granules?
Yes, but C. diphtheriae is the primary target.
What if granules appear faint?
May indicate poor staining or low granule content.
Can old cultures be used for Albert staining?
No, younger cultures (18-24 hrs) show better granule formation.
Which culture media enhance granule formation?
Loeffler’s serum medium or tellurite agar.
What if the background is too dark?
Over-staining or insufficient washing may be the cause.
Can Albert staining be automated?
No, it’s a manual staining technique.
Is Albert staining used only for C. diphtheriae?
Mostly, but it can detect granules in other bacteria.
Can Albert staining replace PCR for diphtheria diagnosis?
No, it’s a presumptive test; PCR or toxin testing is confirmatory.
What are the limitations of Albert staining?
Cannot differentiate toxigenic vs. non-toxigenic C. diphtheriae.
Can Albert staining be used for environmental samples?
Yes, but clinical samples (throat swabs) are more common.
Is Albert staining used in food microbiology?
Rarely, mostly for clinical diagnostics.
What safety precautions are needed?
Gloves, lab coat, and proper disposal of stained slides.
Can Albert staining detect dead bacteria?
Yes, if granules are preserved.
Why is cedarwood oil used?
For oil immersion microscopy to enhance resolution.
Can Albert staining be combined with other stains?
Usually performed separately from Gram or acid-fast stains.
Where can I find reference protocols for Albert staining?
Koneman’s Color Atlas of Diagnostic Microbiology or clinical lab manuals.
Albert Staining 30 MCQs:
1. What is the primary purpose of Albert staining?
A) To stain Gram-positive bacteria
B) To identify metachromatic granules in Corynebacterium diphtheriae
C) To differentiate acid-fast bacteria
D) To detect bacterial spores
2. Metachromatic granules are composed of:
A) Lipopolysaccharides
B) Polymetaphosphate (Poly-P)
C) Peptidoglycan
D) Glycogen
3. Which dye in Albert Stain 1 binds to metachromatic granules?
A) Malachite green
B) Toluidine blue
C) Safranin
D) Crystal violet
4. What is the role of iodine in Albert staining?
A) Decolorizer
B) Counterstain
C) Mordant
D) Primary stain
5. After Albert staining, the cytoplasm of C. diphtheriae appears:
A) Blue-black
B) Pink
C) Green
D) Purple
6. Which bacteria besides C. diphtheriae may show metachromatic granules?
A) Escherichia coli
B) Yersinia pestis
C) Staphylococcus aureus
D) Streptococcus pyogenes
7. What is the optimal culture medium for enhancing metachromatic granules?
A) MacConkey agar
B) Loeffler’s serum medium
C) Blood agar
D) Mannitol salt agar
8. How long should Albert Stain 1 be applied?
A) 1 minute
B) 3-5 minutes
C) 10 minutes
D) 30 seconds
9. What is the mordant in Albert staining?
A) Acetic acid
B) Iodine
C) Alcohol
D) Malachite green
10. The pH of Albert stain is adjusted to:
A) 7.0
B) 2.8
C) 9.5
D) 5.0
11. Which of the following is NOT a component of Albert Stain 1?
A) Toluidine blue
B) Malachite green
C) Iodine
D) Glacial acetic acid
12. What is the correct order of steps in Albert staining?
A) Stain → Wash → Mordant → Observe
B) Mordant → Stain → Wash → Observe
C) Stain → Mordant → Wash → Observe
D) Decolorize → Counterstain → Wash → Observe
13. What magnification is used to observe Albert-stained slides?
A) 40X
B) 100X (oil immersion)
C) 400X
D) 1000X
14. Which of these stains is an alternative to Albert staining for metachromatic granules?
A) Gram stain
B) Neisser’s stain
C) Ziehl-Neelsen stain
D) India ink stain
15. What happens if the slide is washed after Albert Stain 1 but before iodine?
A) Better staining
B) No effect
C) Stain washes off, reducing clarity
D) Background becomes darker
16. Which shape does C. diphtheriae exhibit under the microscope?
A) Chains of cocci
B) Clusters
C) “V” or “L” arrangements
D) Spiral-shaped
17. What is the function of malachite green in Albert Stain 1?
A) Stains granules
B) Stains cytoplasm
C) Acts as a decolorizer
D) Fixes the smear
18. Why is acetic acid added to Albert Stain 1?
A) To increase pH
B) To decrease pH (make it acidic)
C) To act as a mordant
D) To prevent contamination
19. What is the storage condition for Albert stain?
A) Frozen at -20°C
B) Room temperature, away from light
C) Refrigerated at 4°C
D) Heated before use
20. What does a negative Albert stain indicate?
A) Presence of C. diphtheriae
B) Absence of metachromatic granules
C) Gram-negative bacteria
D) Acid-fast bacteria
21. Which disease is diagnosed using Albert staining?
A) Tuberculosis
B) Diphtheria
C) Cholera
D) Typhoid
22. What is the chemical nature of metachromatic granules?
A) Lipids
B) Proteins
C) Inorganic polyphosphates
D) Carbohydrates
23. How should the smear be fixed before staining?
A) Alcohol wash
B) Heat fixation
C) Formalin treatment
D) Freezing
24. What is the role of alcohol in Albert Stain 1?
A) Decolorizer
B) Solvent for dyes
C) Fixative
D) Buffer
25. Which part of C. diphtheriae stains bluish-black?
A) Cell wall
B) Cytoplasm
C) Metachromatic granules
D) Capsule
26. What precaution should be taken with iodine solution?
A) Store in sunlight
B) Keep in a dark bottle
C) Freeze before use
D) Heat before staining
27. Which staining technique is similar to Albert stain in targeting granules?
A) Gram stain
B) Endospore stain
C) Pugh’s stain
D) Capsule stain
28. What is the final step before microscopic observation?
A) Blot drying
B) Re-staining
C) Decolorizing
D) Heating
29. Albert staining is a type of:
A) Simple stain
B) Differential stain
C) Negative stain
D) Fluorescent stain
30. Which component of Albert Stain 2 acts as a mordant?
A) Potassium iodide
B) Iodine
C) Water
D) Alcohol
