Protozoa in feces
Apr 24, 2018
Detection and differentiation of protozoa( distinction of pathogenic forms from non-pathogenic ones) is a rather complicated task. Most unicellular organisms in feces are found in two forms: vegetative( the trophozoite stage) - active, mobile, vital, easily susceptible to harmful effects( in particular, cooling) and therefore rapidly dying after isolation from the intestine, and in the form of cysts resistant to external influencesoocyst).In feces the simplest , as a rule, is found only in the incised state;for detection of vegetative forms it is necessary to investigate feces still in a warm state. This is due to the fact that in the stale feces the vegetative forms of the protozoa quickly die and the dead quickly respond to the action of proteolytic enzymes, and as a result lose their characteristic features of structure. In addition, during cooling, the mobility of protozoa decreases, and then disappears - an important auxiliary factor in their differentiation.
In feces it is possible to identify 20 species of protozoa( 8 pathogenic and conditionally pathogenic and 12 commensals).The simplest intestines live in the small or large intestine in the stage of trophozoite and / or cyst. They belong to one of 4 groups: amoebas, flagella, ciliated and coccidia.
Entamoeba histolytica( dysentery amoeba) causes amoebiasis in a person. It is localized in the large intestine, it is released in the form of trophozoite( with liquid feces) and / or cysts( in a decorated stool).Due to the fact that most species of amoebas( intestinal, Hartmann, Buçli) are not pathogenic for humans, caution should be exercised when assessing the results of a study of faeces. Only the detection of trophozoite-haematophagus( E. histolytica forma magna tissue form) can serve as a reliable indication of the presence of amebic dysentery and / or amoeic ulcerative colitis in the patient. The presence of erythrocytes in the protoplasm is a very important diagnostic feature, since the non-pathogenic forms of amoebas never contain them.
In all other cases, the detection of E. histolytica-like forms of trophozoites that do not contain erythrocytes, is not a basis for the diagnosis of amoebiasis as a disease. Similarly, the results of detection of only E. histolytica cysts( luminal form), which can be detected in persons recovering from acute amebiasis, in patients with chronic amoebiasis and in carriers, are also evaluated.
Lamblia intestinalis( lamblia) belongs to the class of flagella. Lamblias are parasitic in the small intestine, mainly in the duodenum, as well as in the gallbladder. The existence of trophozoites( vegetative form of lamblia) requires a liquid medium, therefore, when entering the large intestine, the lamblia are encysted, and only the cysts are found in the stool. Only with profuse diarrhea or after the action of laxatives in feces can you find vegetative forms.
Balantidium coli. Balantidium is the only ciliated infusoria that parasitizes the human intestine and causes diseases of varying severity - from mild colitis to severe ulcerative lesions. The causative agent is found in feces in the form of trophozoites or cysts. Perhaps the carriage in healthy people.
Cryptosporidium. Representatives of the genus Cryptosporidium are now considered to be the most important pathogens of diarrhea. Cryptosporidia( from the Greek "hidden dispute") - obligate parasites that infect the microvilli of the mucous membranes of the gastrointestinal tract and the airways of humans and animals. GI infections caused by cryptosporidia are registered in all countries of the world. Such a wide distribution of cryptosporidiosis is associated with a large number of natural reservoirs of infection, a low infectious dose and high resistance of the pathogen to disinfectants and antiparasitic drugs.
Cryptosporidium parvum and Cryptosporidium felis are potentially pathogenic to humans among cryptosporidia( detected in HIV-infected individuals).The most typical localization of infection in humans is the distal parts of the small intestine. In patients with expressed immunodeficiencies, all of the gastrointestinal tract can be infected - from the oropharynx to the mucosa of the rectum.
Diagnosis of cryptosporidiosis in most cases is based on the detection of cryptosporidia oocysts in feces and / or( significantly less frequently) in the biopsy specimen of the small intestine mucosa in the syndrome of watery diarrhea. Use microscopy of prepared preparations stained by Gram. In most cases, this method of coloring does not allow the identification of oocysts, due to their weak ability to retain the dye and the inability to distinguish them from yeast-like fungi. Therefore, apply the coloration to acid resistance. With this method of coloring, the cryptosporidia oocysts are painted red or pink and are clearly visible on a blue-violet background in which other microorganisms and intestinal contents are stained.
In acute cryptosporidiosis, the amount of oocysts in the feces is large, which makes it easy to detect them when microscopically colored preparations. However, in chronic cryptosporidiosis with a light course, when the amount of oocysts in the feces is small, in order to increase the probability of their detection it is necessary to use enrichment techniques. In recent years, serological methods have often been used to diagnose cryptosporidiosis.
Cryptosporidiosis of the biliary tract can be manifested by cholecystitis, much less often with hepatitis( with increased bilirubin concentration, AST activity, ALT, alkaline phosphatase in the blood) and sclerosing cholangitis. For the diagnosis of biliary cryptosporidiosis, liver and bile biopsy specimens are examined, where cryptosporidia can be detected at various stages of development.
To monitor the effectiveness of treatment of protozoal intestinal lesions, feces are examined depending on the detected disease: in amebiasis, balantidiasis - immediately after treatment, with giardiasis - after 1 week. After treatment of invasions of biliary tract, control of efficacy can be carried out both in the study of stool and bile.