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Year : 2003  |  Volume : 21  |  Issue : 2  |  Page : 143
 

A novel method for demonstration of bacterial and yeast capsule


Department of Microbiology, Government Medical College, Nagpur - 440 012, Maharashtra, India

Correspondence Address:
Department of Microbiology, Government Medical College, Nagpur - 440 012, Maharashtra, India



How to cite this article:
Kapale S, Chaudhary H, Chande C, Shrikhande S, Fule R P. A novel method for demonstration of bacterial and yeast capsule. Indian J Med Microbiol 2003;21:143


How to cite this URL:
Kapale S, Chaudhary H, Chande C, Shrikhande S, Fule R P. A novel method for demonstration of bacterial and yeast capsule. Indian J Med Microbiol [serial online] 2003 [cited 2019 Jun 15];21:143. Available from: http://www.ijmm.org/text.asp?2003/21/2/143/7998


Dear Editor,
The conventional staining techniques routinely used for staining bacteria in blood, serous fluids, pus and from cultures are not very helpful for revealing presence of capsule. The best method in practice for staining capsule on bacteria and yeast like Cryptococcus is the wetfilm India ink method.[1] This technique needs some practice to make satisfactory film of correct thickness, else the capsule is obscured by the overlying ink. A supply of suitable and finely granular ink is also needed. The bodies of bacteria are not stained with India ink and their outlines are only faintly visible under the ordinary microscope.
We describe here a rapid and simple technique for demonstration of capsule of bacteria and yeast in the specimen and also from cultures.
1. A thin uniform film of fluid or bacterial culture in saline is made on a perfectly clean, grease-free slide, dried in air and fixed by heat.
2. Film is covered with carbol fuchsin (Ziehl Neelsen's Carbol fuchsin diluted 1:3 with distilled water) for one minute.
3. The stain is washed off with tap water and smear is dried with blotting paper.
4. A drop of 10% nigrosin made in distilled water is put at one end of the film and spread evenly by drawing a film with the edge of cover slip. The film is dried in air and observed under oil immersion objective.
The bacteria and yeast cells are stained dark pink with carbol fuchsin and capsule appears as clear zone between bacterium or yeast cells and grayish black background of nigrosin.
It is essential that the nigrosin is drawn into a thin and even film otherwise, the organism inside the capsule becomes invisible and only empty spaces can be seen in the grayish black nigrosin background. This staining method is technically very simple and unlike conventional negative staining techniques the organisms are brightly stained inside the capsule and hence the unstained capsule is clearly delineated around the stained organism against the background of nigrosin. This technique is as rapid as conventional India ink method and thus useful for the demonstration of capsule of the organism in specimen and especially in culture. We recommend its routine use for rapid identification of capsulated organisms like Streptococcus pneumoniae and Cryptococcus neoformans in specimen like CSF, pus, and in cultures. 

 ~ References Top

1.Duguid JP. Staining Methods In: Mackie and McCartney Practical Medical Microbiology, 13th ed. Collee JG, Duguid JP, Fraser AG, Marmion BP. Eds. (Churchill Livingstone, London) 1989:51.  Back to cited text no. 1    
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2004 - Indian Journal of Medical Microbiology
Published by Wolters Kluwer - Medknow

Online since April 2001, new site since 1st August '04