Wayson stain

Wayson Stain

Yersinia pestis stained with Wayson stain

The Wayson stain is a bacteriological stain used primarily for the identification of Yersinia pestis, the causative agent of plague. This staining technique is particularly useful in microbiology for its ability to highlight the bipolar staining characteristic of Yersinia species, which appear as "safety pin" shaped organisms under the microscope.

History

The Wayson stain was developed by Edward Francis Wayson, a bacteriologist who sought to improve the visualization of Yersinia pestis in clinical specimens. The stain has been instrumental in the diagnosis of plague, especially in endemic regions.

Composition and Preparation

The Wayson stain is composed of basic fuchsin, methylene blue, and a mordant, typically phenol. The preparation involves mixing these components in specific proportions to achieve the desired staining effect. The stain is applied to a bacterial smear, which is then examined under a light microscope.

Staining Procedure

1. Prepare a thin smear of the specimen on a glass slide. 2. Fix the smear by gently heating it. 3. Flood the slide with Wayson stain and allow it to sit for a specified time, usually around 2 minutes. 4. Rinse the slide gently with water to remove excess stain. 5. Air dry the slide and examine under a microscope.

Microscopic Appearance

Under the microscope, Yersinia pestis stained with Wayson stain exhibits a characteristic bipolar appearance, often described as resembling a "safety pin." This is due to the differential uptake of the stain by the bacterial cell, with the ends of the bacilli appearing darker than the center.

Applications

The primary application of the Wayson stain is in the identification of Yersinia pestis in clinical and environmental samples. It is particularly useful in field settings where rapid diagnosis is critical. The stain can also be used to identify other bacteria that exhibit similar staining characteristics, although its specificity for Yersinia pestis makes it a valuable tool in plague diagnostics.

Limitations

While the Wayson stain is effective for identifying Yersinia pestis, it is not specific to this organism alone. Other bacteria may also exhibit bipolar staining, which can lead to false positives. Therefore, additional confirmatory tests, such as polymerase chain reaction (PCR) or culture, are often required to confirm the presence of Yersinia pestis.

Related Pages

• Yersinia pestis
• Plague
• Bacteriological stain
• Microscopy