What is the principle of Neisser stain?
The principle of the Neisser stain lies in its ability to specifically visualize polar bodies (also known as metachromatic granules or Babes-Ernst bodies) within the cytoplasm of certain bacteria, particularly Corynebacterium diphtheriae. This differential staining technique allows these granules, rich in polymetaphosphate, to appear distinctly colored from the rest of the bacterial cell.
Understanding the Principle of Neisser Stain
The Neisser stain is a crucial microbiological technique designed to aid in the identification of specific bacteria, notably Corynebacterium diphtheriae, the causative agent of diphtheria. Its principle hinges on the unique staining characteristics of polar bodies found in these organisms.
Key Aspects of the Principle:
- Visualization of Polar Bodies: The primary goal is to make these highly condensed phosphate reserves visible. These structures are often located at the poles of the bacterial cell.
- Differential Staining: The stain utilizes a combination of dyes that react differently with the polar bodies compared to the bacterial cytoplasm. This difference in staining affinity creates the necessary contrast.
- Metachromatic Property: While not explicitly stated in the provided reference, the effectiveness of the Neisser stain is due to the metachromatic nature of these granules. Metachromasia is the phenomenon where a substance stains a different color from that of the dye being used.
The Staining Mechanism
The Neisser staining process involves a two-step procedure using specific dyes under particular conditions:
-
Primary Staining:
- Cells are initially treated with a mixture of methylene blue and crystal violet in an acidic solution.
- In this acidic environment, the polar bodies, due to their high concentration of polymetaphosphate, readily absorb and retain these basic dyes, often appearing dark blue or purple.
-
Counterstaining:
- Following the primary stain, a counterstain, typically chrysoidin solution, is applied.
- The chrysoidin stains the general bacterial cytoplasm and cell body a contrasting color (often yellow or brownish-yellow), making the distinctly stained polar bodies stand out clearly.
Role in Bacterial Identification
As highlighted in the reference, the Neisser stain is specifically "used to identify diphtheria bacteria." The presence and characteristic appearance of prominent polar bodies stained dark blue/purple against a yellow/brownish bacterial cell are strong indicators for the presumptive identification of Corynebacterium diphtheriae in clinical samples. This makes the Neisser stain an invaluable tool in microbiology laboratories.
Summary of Staining Components
To illustrate the components and their roles in the Neisser staining process:
| Staining Step | Reagents Used | Purpose / Outcome |
|---|---|---|
| Primary Stain | Methylene Blue & Crystal Violet | Stains polar bodies intensely (dark blue/purple) |
| Solution Type | Acidic solution | Enhances differential uptake by polar bodies |
| Counterstain | Chrysoidin solution | Stains bacterial cytoplasm (yellow/brownish-yellow) |
This differential staining property allows microbiologists to quickly visualize these characteristic inclusions, which are vital for the presumptive diagnosis of diphtheria.
