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Questions and Answers
Describe the steps of Gram staining a skin specimen?
Describe the steps of Gram staining a skin specimen?
The steps of Gram staining a skin specimen include: 1. Fixing the specimen with heat or alcohol. 2. Applying crystal violet stain for 1 minute. 3. Rinsing with water. 4. Applying iodine for 1 minute. 5. Rinsing with water. 6. Decolorizing with alcohol. 7. Counterstaining with safranin for 1 minute. 8. Rinsing with water and blotting dry.
What are the morphological features of common anaerobes as seen on Gram stain?
What are the morphological features of common anaerobes as seen on Gram stain?
The morphological features of common anaerobes as seen on Gram stain include: 1. Small size. 2. Variable shape (pleomorphic). 3. Lack of spores. 4. Lack of oxygen requirement for growth.
Describe the handling of anaerobic specimen in the laboratories?
Describe the handling of anaerobic specimen in the laboratories?
The handling of anaerobic specimen in the laboratories involves minimizing exposure to oxygen by using anaerobic chambers or gas packs, and ensuring prompt transport to the laboratory in anaerobic transport media or containers.
What are the steps in the preparation of a KOH mount?
What are the steps in the preparation of a KOH mount?
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What is the recommended method for collection of skin specimen in fungal infections?
What is the recommended method for collection of skin specimen in fungal infections?
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Study Notes
Gram Staining a Skin Specimen
- Begin by preparing a clean glass slide and place a small amount of the skin specimen on it.
- Allow the specimen to air dry completely before passing the slide briefly through a flame to fix the sample.
- Stain the slide with crystal violet dye for one minute, then rinse with water to remove excess dye.
- Apply iodine solution for one minute, which acts as a mordant, enhancing the crystal violet staining.
- Rinse the slide again with water, then decolorize by applying alcohol or acetone until the slide runs clear.
- Rinse quickly with water to halt the decolorizing process, then counterstain with safranin for one minute.
- Final rinse with water and allow the slide to dry before examining under a microscope.
Morphological Features of Common Anaerobes on Gram Stain
- Anaerobes can appear as Gram-positive or Gram-negative cocci or rods.
- Common examples include Clostridium (Gram-positive bacilli) which often exhibit characteristic boxcar shapes.
- Bacteroides species present as Gram-negative pleomorphic rods, typically found in clusters.
- Morphological details of anaerobes may include lack of motility and spore formation in certain species.
Handling of Anaerobic Specimens in Laboratories
- Collect specimens using special anaerobic collection devices or systems to prevent exposure to oxygen.
- Transport specimens in anaerobic transport media and process them promptly to maintain viability.
- Avoid opening anaerobic containers in the presence of air, which can compromise the samples.
- Store specimens at appropriate temperatures to prevent overgrowth of organisms and degradation of anaerobic conditions.
Preparation of a KOH Mount
- Start by placing a small amount of the specimen (e.g., skin scraping or nail clippings) on a glass slide.
- Add one or two drops of 10-20% potassium hydroxide (KOH) solution to the specimen.
- Gently heat the slide to facilitate the clearing of keratin and other debris without boiling.
- Allow the slide to sit for about 10-15 minutes for optimal visualization of fungal elements.
- Examine under a microscope for the presence of hyphae or spores.
Recommended Method for Collection of Skin Specimen in Fungal Infections
- Collect specimens using sterile instruments to avoid contamination, ideally during the active phase of infection.
- Skin scrapings should include the edge of the lesion, where fungal growth is often abundant.
- Use swabs to collect samples from moist areas, ensuring adequate pressure to absorb material.
- Place collected specimens immediately into sterile containers to preserve fungal elements for laboratory analysis.
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Description
Test your knowledge of skin and soft tissue infections in this microbiology lab quiz. Learn about specimen collection, Gram staining, interpretation of findings, and preparation of KOH mounts for fungal infections.
