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...
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...
Overview: Streptococci are Gram-positive cocci, non-motile, non-spore-forming bacteria arranged in pairs or chains in structure. Most of the streptococci are facultative anaerobes and some are obligative anaerobe it requires enriched media (Blood agar). Streptococci are catalase-negative and oxidase negative and the sole product of glucose fermentation is lactic acid with no gas formation is called homofermentative. Streptococcal species may be serologically classified on the basis of cell surface carbohydrate antigens (either cell wall polysaccharides (group A, B, C, F and G streptococci) or (are cell wall lipoteichoic acid (group D Enterococcus sp .). other streptococci are viridans group. Virulence factor: Group A Streptococci M- protein are acid and head stable, tripsin- labile, fibrillar proteins are associated with the outer surface of the cell wall. Hyaluronic acid capsule function to help the organism resist the complement dependent killing by phagocytic...
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