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Chapter: 12th Microbiology : Practical Experiment Manual

Spotters: Slide

6. Cyst of Entamoeba histolytica 7. Penicillium species 8. Microfilariae 9. Egg of Ascaris lumbricoides 10. Heterocysts of Nostoc 11. Acid fast bacilli

B) Slide

6. Cyst of Entamoeba histolytica

• Cyst is one of the three forms of entamoeba histolytica

• A mature cyst is a quadrinucleate spherical bod

• Mature cysts are passed in the stool of infected person

• Direct examination of wet mount of stool for cysts is diagnostic of intestinal amoebiasis


7. Penicillium species

• Colony of penicillium are initially white and fluffy and later produce pigmented spores and turn into shades of green or blue green

• Hyphae are hyaline and septate

• Condiophores are long, give rise to branching phialids

• Phialids branch and give the appearance of brush or penicillins

They produce sterigmata bearing chain of conidia (spores) which are oval or spherical and measure 1-2micrometer.


8. Microfilariae

• Filariasis is caused by nematodes (roundworms) like Wuchereria bancrofti that inhabit the lymphatics and subcutaneous tissues.

• The female worms release the firsstage larvae called microfilariae, which are detected in the peripheral blood.

• Identification of microfilariae by microscopic examination is the most practical diagnostic procedure.

• The blood sample can be a thick smear, stained with Giemsa.

• The larva measures about 290microns in length and 6-7micron in breath.


9. Egg of Ascaris lumbricoides

• These are passed in stool of the infected host.

• Brownish due to bile pigment.

• Fertilised eggs are rounded and have a thick shell (chitinous).

• Unfertilised eggs are elongated and larger than fertile eggs.

 • When ingested through water or contaminated food by human it causes Ascariasis.

• Microscopic identification of eggs in the stool is the most common method for diagnosing intestinal ascariasis.


10. Heterocysts of Nostoc

• Heterocysts are specialized structures having thick cell wall formed in some filamentous blue green algae like Nostoc, Anabena.

• They may be terminal or found in between the vegetative cells attached to it by means of pores.

• They are sites of atmospheric nitrogen fixation.

• They serve as a store house of food material.


11. Acid fast bacilli

• Acid fast bacilli contains mycolic acid in their cell walls hence do not get stained easily, however once stained cannot be decolourised easily.

• Special method like Ziehl- Neelson’s Carbol fuchsin is used to stain acid fast bacilli.

• The acid- fast bacilli are stained red in colour while the non acid fast cells appear blue when counterstained with methylene blue.

• Mycobacterium tuberculosis is and acid fast bacilli.


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