Protozoa trophozoites

The direct wet mount made from unconcentrated fresh feces is most useful for the detection of the motile trophozoites of intestinal protozoa and the motile larvae of Strongyloides spp. It is also useful for the detection of protozoan cysts and helminth eggs. For fixed feces, the direct wet mount may allow the detection of parasites which do not concentrate well. This method is also useful for the examination of specific portions of feces, such as flecks of blood or mucus. 

In an ideal stain, the cytoplasm of cysts and trophozoites is blue-green tinged with purple. Entamoeba coli cyst cytoplasm is often more purple than that of other species. Nuclear chromatin, chromatoid bodies, erythrocytes, and bacteria stain red or purplish red. Other ingested particles such as yeasts often stain green. Parasite eggs and larvae usually stain red. Inflammatory cells and tissue cells stain in a fashion similar to that of protozoa. Color reactions may vary from the above. 

As opposed to the prokaryotic bacteria, protozoa are a diverse set of eukaryotic organisms, often with complex life cycles. These entities exist in various forms, from proliferative trophozoites through to dormant cysts, and some spending their... 

Trophozoite—The amoeboid, vegetative stage of the malaria protozoa. 

It is a nonpathogenic protozoa of the large intestine of man also distributed throughout the world. The flagellate is present only in the trophozoite form. The parasite may be seen in very large numbers in stool during diarrhea of nonparasitic etiology. 

Amebiasis ajfects 10% of the world s population. In the U.S., amebiasis is usually seen in those living in crowded, unsanitary conditions. Entamoeba dispar accounts for 90% of human infections and E. histolytica/or only 10%, but only E. histolytica causes human disease. Humans are the only known hosts for these protozoa, which are transmitted almost exclusively by the fecal-oral route. E. histolytica cysts ingested from contaminated food or water transform into trophozoites that reside in the large intestine. Many individuals infected with E. histolytica are asymptomatic but excrete infectious cysts, making them a source for further infections. In others, E. histolytica trophozoites invade the colonic mucosa with resulting colitis and bloody diarrhea (amebic dysentery). Rarely, E. histolytica trophozoites invade through the colonic mucosa and reach the liver via the portal circulation, where they establish an amebic liver abscess. 

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