Methods of preparation of stool for microscopic examination

 

 Methods of preparation of stool for microscopic examination

        Ans: The method for the preparation of stool for microscopy include:-

 (a). saline preparation: Take a little foecal material on a slide, Mix with normal saline (0.85%) tomake a thin emulsion. Cover it with a cover slip. The thickness should be such that one  should be able to see print through it.

(b). Iodine preparation: This is done as above using Gram’s iodine instead of saline. Iodine is used to examin the nuclear structure of cyst. It stain the chromatin granules of karysone of amoebic cyst brown. The glycogen vavoule also is stained brown. Iodine kills living material, motility of parasites will not be detected. In routine use iodine preparation is complementary to the saline preparation.

 (c). stool concentration method: These method are used to identify ova & cysts which are few in number and not detected by routine method.

                The method used are:-

(i). Flootation method: The stool is mixed with zinc sulfate or magnesium sulfate which has a  high sp gravity so that the parasite flouts in the solution. It is useful to                                           concentrate cysts, larval, most helminthic eggs.

                Zinc sulphate concentration method:-

                Reagents:- Zinc sulphate solution of sp gravity 1.80 is needed. It is prepared by                                dissolving 33gm of the chemical in 100ml of D/W.

                Method:- mix a small piece of stool with about 100ml of water or saline in a bottle or                        tube.

ü  Sieve the suspension into a beaker, through a strainer with small holes.

ü  Pour the contents of the beaker into a centrifuge tube.

ü  Centrifuge at 2000-3000 rpm/min for 1 min.

ü  Pour off the supernatant fluid.

ü  Resuspend the deposit in clean water and add enough water to fill the tube.

ü  Mix will and re-centrifuge.

ü  Pour of the supernatant fluid.

ü  Resuspunded in zinc sulphate solution, fill the test tube with solution.

ü  Centrifuge at high speed for min.

ü  Transfer the contents from the surface of the tube to a slide using a bacteriological wire loop. This surface film must be removed immediately.

ü  Add small drops of saline and mix.

ü  Cover with a coverslip.

ü  Examine under 10x and 40x objective.