All the following organisms lack capsule except:
Correct Answer: Cryptococcus neoformans
Description: Ans: B (Cryptococcus neoformans) Ref: Ananthnarayan R. Paniker CKJ. Textbook of Microbiology. 8th Edition. Hyderabad: Universities Press: 2009. Pg. 19. 607-12. Explanation: Some bacteria have a layer of material lying outside the cell wall. When the layer is well organized and not easily washed off, it is called a capsule. A slime layer is a zone of diffuse, unorganized material that is removed easily. Capsules and slime layers usually are composed of polysaccharides, but Bacillus anthracis has a capsule of poly-D-glutamic acid. Some bacteria may have both a capsule and a slime layer (for example. Streptococcus salivarius). Special capsule staining techniques are available, usually employing copper salts as mordants. Capsules may be readily demonstrated by negative staining in wet films with India ink. Histoplasma capsulatum: It is a dimorphic fungus which causes intracellular infection of the reticuloendothelial system. Blood and marrow smear stained with Giemsa or calcofluor white stain show intracellular 2-4 pm budding yeast cells (within macrophages or histiocytes). It was initially believed to possess a capsule and was named as H. capsulatum. However, it was later found that it does not have a capsule. Cryptococcus neoformans : It is a round budding cell, 4-20 urn in diameter, with a prominent polysaccharide capsule. It is a soil saprophyte and is particularly abundant in the feces of pigeons and other birds. The capsule can be demonstrated as a clear halo by India ink. Candida albicans : Candida albicans is an ovoid or spherical budding cell, which produces pseudomvcelia both in culture and in tissues. Candida albicans is a pathogenic yeast-like fungus. Coccidioides immitis : The fungus is dimorphic, occurring in the tissue as a yeast and in culture (both at 37degC and at room temperature) as the mycelial form. The tissue form is a spherule, 15-75 pm in diameter, w ith a thick doubly refractile wall and filled with endospores
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