Staining of microorganisms Flashcards
What is the primary complaint of the 33-year-old female patient?
Chronic shortness of breath on exertion
The patient has a history of similar symptoms and was previously diagnosed with acute bronchitis.
What significant finding was reported in the CT scan of the patient’s chest?
Diffuse centrilobular micronodular pattern without focal consolidation
This finding is relevant for diagnosing potential pulmonary issues.
What microorganism was identified in the cytology of the bronchoalveolar lavage?
Histoplasma capsulatum
This organism is associated with respiratory infections and is often found in certain environmental conditions.
List the four groups of micro-organisms that are medically important and of interest to histotechnology.
- Bacteria
- Fungi (Yeasts)
- Viruses
- Protozoa
What is the cell wall composition of bacteria?
Composed of peptidoglycan (mucopolysaccharide)
This structure is crucial for bacterial integrity and function.
How are bacteria classified?
- Shape
- Arrangement or formation
- Gram stain reaction (Gram positive vs Gram negative)
- Other stains (e.g., Acid-Fast techniques)
What are the three main shapes of bacteria?
- Cocci
- Bacilli
- Spirochetes
What are the two most common differential staining techniques?
- Gram Stain
- Acid-fast stains
What is the purpose of running control slides when performing a Gram stain?
To ensure the accuracy of the staining technique and tissue sample
Control slides should be known positive for the type of organism being demonstrated.
What is the preferred fixative for Gram staining?
10% neutral buffered formalin
Proper fixation is essential to preserve tissue morphology.
What color do Gram positive and Gram negative organisms appear in a Gram stain?
- Gram positive: blue
- Gram negative: red
What are the differences between Gram positive and Gram negative bacteria?
- Gram positive: thicker cell wall (15-25 nm), more layers of peptidoglycan
- Gram negative: thinner cell wall (8-12 nm), irregular layer of lipoprotein
What is the principle behind the Gram stain procedure?
Differentiates bacteria based on their cell wall properties and porosity
The staining process involves a series of steps that lead to different colors based on bacterial type.
What is the purpose of the Ziehl-Neelsen technique?
To demonstrate acid-fast bacteria in tissue sections
This technique is particularly useful for identifying Mycobacterium species.
What is the chemical that forms a strong union with basic fuchsin in acid-fast staining?
Mycolic acids
These lipids are crucial for the retention of the stain in acid-fast bacteria.
What color do acid-fast bacilli appear in the Ziehl-Neelsen stain?
Red
The background typically stains blue.
What is the Warthin-Starry technique used for?
Demonstration of spirochetes in tissues
This method uses silver staining to visualize these organisms.
What is the role of hydroquinone in the Warthin-Starry technique?
Chemical reducer that allows spirochetes to bind to silver ions
This is part of the argyrophilic staining method.
What are the expected results of the Warthin-Starry technique?
- Spirochetes: black
- Nuclei: brown
- Background: golden yellow
What is the Kinyoun method known for?
It is a cold method for acid-fast staining that uses a more concentrated primary stain
This method does not require heating.
What color do spirochetes stain in the Warthin-Starry technique?
black
In the Warthin-Starry technique, spirochetes are demonstrated as black.
What is the preferred fixative for the Warthin-Starry technique?
10% NBF
Mercurial and chromate fixatives should always be avoided.
What is the principle behind the Warthin-Starry technique?
Argyrophilic organisms are demonstrated by absorbing silver from solution with a reducing agent
The reducing agent used is hydroquinone.
What are the results of the Warthin-Starry technique for Helicobacter pylori?
dark brown/black
Other bacteria also stain dark brown/black.
