Ziehl–Neelsen staining is a bacteriological stain used to identify acid-fast organisms, mainly Mycobacteria. It is named for two German doctors who modified the stain: the bacteriologist Franz Ziehl (1859–1926) and the pathologist Friedrich Neelsen (1854–1898).
Types of Staining Techniques
| Sr. No. | Staining Technique |
|---|
| 1. | Simple (Monochrome) |
| 2. | Negative (Relief) |
| 3 | Gram |
| 4 | Acid fast (Ziehl-Neelsen technique) |
Three criteria for identifying and classifying the most commonly known types of stains are type of edge, feel and colour. All stains cannot be recognized by the appearance of the edge. Here we distinguish between hard and soft stains. Hard stains are caused by Varnish, oil paints and glues.
Methylene blue (C.I. 52015; Basic blue 9) is a basic thiazine dye. It may have more scientific uses than any other dye. As a simple stain, applied from a mildly acidic solution (pH 3 to 4) it colors nucleic acids and acidic carbohydrates.
Simple Staining
| Characteristics | Direct staining | Indirect staining |
|---|
| Stain used | Basic stain | Acidic stain |
| Charge of stain | Positive | Negative |
| Examples | Methylene blue, crystal violet, carbol fuschin | Nigrosine, india ink, congo red |
| Outcome | Stains the specimen | Stains the background |
The staining method uses crystal violet dye, which is retained by the thick peptidoglycan cell wall found in gram-positive organisms. This reaction gives gram-positive organisms a blue color when viewed under a microscope.
The three basic bacterial shapes are coccus (spherical), bacillus (rod-shaped), and spiral (twisted), however pleomorphic bacteria can assume several shapes.
Escherichia coli (E. coli) is a Gram-negative, rod-shaped, facultative anaerobic bacterium. This microorganism was first described by Theodor Escherich in 1885.
The performance of the Gram Stain on any sample requires four basic steps that include applying a primary stain (crystal violet) to a heat-fixed smear, followed by the addition of a mordant (Gram's Iodine), rapid decolorization with alcohol, acetone, or a mixture of alcohol and acetone and lastly, counterstaining with
Bacteria with thick cell walls keep the first (purple) stain and are called Gram positive. Thin walled bacteria cannot keep the first stain (purple) so when the second stain (red) is placed on the organisms they become red or Gram negative.
PURPOSE: Used in the demonstration of acid-fast bacteria belonging to the genus 'mycobacterium', which include the causative agent for tuberculosis. PRINCIPLE: The lipoid capsule of the acid-fast organism takes up carbol- fuchsin and resists decolorization with a dilute acid rinse.
INTRODUCTION. There are five medically important genera of gram-positive rods: Bacillus, Clostridium, Corynebacterium, Listeria, and Gardnerella. Bacillus and Clostridium form spores, whereas Corynebacterium, Listeria, and Gardnerella do not.
- Types of staining techniques. Simple staining.
- Differential staining. (Use of of single stain)
- (Use of two contrasting stains) Direct.
- Indirect. Separation.
- Visualization. (Positive)
- (Negative) into groups. of structures.
- Gram stain. Flagella stain.
- Acid fast. Capsule stain.
Some stains can penetrate cell walls and highlight cell components, and this can help scientists visualize metabolic processes. Stains also help distinguish between live cells and dead ones. Moreover, staining allows scientists count the number of cells of a particular type within a certain biomass.
A chemical used to add pigment to the nuclear or acidic components of cells.
Bacterial organisms are so small that most of them are visible only under a microscope with a magnification power of 1000X. However, mere magnification of size does not provide a sufficient degree of clarity, so that bacteria must therefore be stained before observation to provide the clarity needed for visualization.
Eosin is the most common dye to stain the cytoplasm in histology. It is an acidic dye that binds to basic components of a cell, mainly proteins located in the cytoplasm. It gives a bright pink color that contrasts that dark blue nuclear hematoxylin staining (Fig. 1.3B).
