Yeast Cells on Gram Stain Gram Positive: Introduction, Procedure and Result-Interpretation

Yeast cell

Gram Reaction of Yeast Cells

All fungi are gram-positive and thus yeast cells of Candida albicans are also positive. The above picture is showing Gram-positive single and budding yeast cells of Candida albicans in Gram-stained Candida as seen with 100X objective.

Requirements for Gram Stain

a) Compound light microscope

b) Reagents and glasswares

  • Bunsen flame
  • Wire loop
  • Clean grease-free slides
  • Marker pen
  • Crystal violet (Basic dye)
  • Gram’s iodine(mordant)
  • 95% ethanol (decolorizing agent)
  • 1% safranin

 

d) Specimen (growth of Candida albicans on SDA)

Preparation of  Smear

  1. Take a clean, and grease-free slide for making a smear.
  2. With an inoculating loop touch the colony and make a smear.
  3. Allow the smear to air dry.
  4. Heat fix the smear while holding the slide at one end, and by quickly passing the smear over the flame of the Bunsen burner two to three times.

Procedure of Gram Stain

  1. Cover the smear with crystal violet and allow it to stand for one minute.
  2. Rinse the smear gently under tap water.
  3. Cover the smear with Gram’s iodine and allow it to stand for one minute.
  4. Rinse smear again gently under tap water.
  5. Decolorize the smear with 95% alcohol.
  6. Rinse the smear again gently under tap water.
  7. Cover the smear again gently with safranin for one minute.
  8. Rinse the smear again gently under tap water and air dry it.
  9. Observe the smear first under the low power (10X) objective, and then under the oil immersion (100X) objective.

Observation

Observe the stained smear.

Result Interpretation of Gram Stain

  1. Gram-positive: purple or violet color
  2. Gram-negative: Pink or red in color
  3. Fungi are also Gram-positive and therefore yeast cells of fungi are positive as shown above image.

 

Further Readings

  1. Bailey & Scott’s Diagnostic Microbiology. Editors: Bettey A. Forbes, Daniel F. Sahm & Alice S. Weissfeld, 12th ed 2007, Publisher Elsevier.
  2. Mackie and Mc Cartney Practical Medical Microbiology. Editors: J.G. Colle, A.G. Fraser, B.P. Marmion, A. Simmous, 4th ed, Publisher Churchill Living Stone, New York, Melborne, Sans Franscisco 1996.
  3.  Manual of Clinical Microbiology. Editors: P.R. Murray, E. J. Baron, M. A. Pfaller, F. C. Tenover and R. H. Yolken, 7th ed 2005, Publisher ASM, USA
  4.  Textbook of Diagnostic Microbiology. Editors: Connie R. Mahon, Donald G. Lehman & George Manuselis, 3rd edition2007, Publisher Elsevier.
  5. Clinical Microbiology Procedure Handbook Chief in editor H.D. Isenberg, Albert Einstein College of Medicine, New York, Publisher ASM (American Society for Microbiology), Washington DC.
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