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KOH Wet Mount Preparation: Purpose, Principle, Procedure, Result Interpretation and uses

Purpose: To identify fungi in clinical specimens such as hair, skin or nails. Principle: The KOH mount is used to aid in detecting fungal elements in thick mucoid material or in specimens containing keratinous materials such as skin scales, nails and hair. The KOH dissolves the background keratin, unmasking the fungus element to make them more apparent. This test cannot find out the exact species of fungi. It can only differentiate whether fungi is present or not and the basic fungal structure. Further tests must be performed to confirm the species of fungi. Type of sample: Sterile containers should be used for sample collection Skin Hair Nail Requirements: Equipment Light microscope (40X magnification) Biological safety cabinet Reagents 10% KOH (aqueous) 40% KOH (aqueous) Cover slip Microscopic slides Procedure for 10% KOH Preparation: Measure the 10g of potassium hydroxide (KOH) pellets, the transfer to container. Add 50ml distilled wa...

Potassium Hydroxide String Test – Principle, Procedure, Uses and Result interpretation

Introduction The potassium hydroxide string test is a very simple, easy to perform and also inexpensive rapid test could be used in addition to the Gram staining for differentiate between Gram positive and negative isolates, where a Gram -negative cell wall are lyses when it’s mixed with a small volume of 3% KOH and releasing viscid chromosomal material from cell, makes the bacterial mixture suspension to become thick viscous or “stringy.” The positive string test indicates a gram negative organism. Hence the alternative name for the test is “String Test”. Some organism like Bacillus and Clostridium sp. appear Gram negative on staining resulting in possible misidentification because of they have lost some of the integrity of their cell wall. Purpose Distinguishing between Gram -negative and Gram -positive organisms Principle In the presence of 3% potassium hydroxide, the cell wall of Gram-negative is broken down. KOH easily dissolves the thin layer of cell walls (Peptidoglycan) o...

India Ink Preparation- Purpose, Principle, Procedure and Result

Purpose: Used for direct microscopic examination of capsules of many microorganism. Principle: India ink or Nigrosin preparation is used for direct microscopic examination of capsules of many microorganisms . The fine granules of the India ink or Nigrosin give an opaque background against which the clear capsules can be easily seen. This technique is particularly useful in visualizing the capsule of Cryptococcus neoformans in cerebrospinal fluid, sputum and other secretions. Required equipment and reagents: Equipments: 1. Bunsen burner 2. Biological safety cabinet 3. Light Microscope – 40 x magnifications Reagents: 1. Cover slip 2. Microscopic slides 3. Nigrosin stain Procedure: 1. Centrifuge CSF specimen lightly to concentrate any microorganisms in the specimen. 2. Em...

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