Piotr Nowak1*, Katarzyna Mastalska1 and Jakub Loster2
1Laboratory of Parasitology, Department of Microbiology, University Hospital in Krakow, 19 Kopernika Street, 31-501 Krakow, Poland
2Department of Infectious Diseases, University Hospital in Krakow, 5 Sniadeckich Street, 31-531 Krakow, Poland
Received: 01 December, 2015; Accepted: 29 December, 2015; Published: 30 December, 2015
Piotr Nowak, Laboratory of Parasitology, Department of Microbiology, University Hospital in Krakow, 19 Kopernika Street, 31- 501 Krakow, Poland, Tel: +4812/4247587; Fax: +4812/ 4247581; E-mail:
Nowak P, Mastalska K, Loster J (2015) Entamoeba histolytica - Pathogenic Protozoan of the Large Intestine in Humans. J Clin Microbiol Biochem Technol 1(1): 010-017.
© 2015 Nowak P, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Entamoeba histolytica; Entamoeba dispar; Entamoeba moshkovskii; Entamoeba histolytica sensu lato; Entamoeba histolytica sensu stricto; commensals of the large intestine; amoebiasis
E. histolytica: Entamoeba histolytica; E. coli: Entamoeba coli; E. nana: Endolimax nana; E. hartmanni: Entamoeba hartmanni; E. polecki: Entamoeba polecki; I. bütschlii: Iodamoeba bűtschlii; ESR: Erythrocyte Sedimentation Rate; ALA Amoebic Liver Abscess; ALT: Alanine Aminotransferase; AST Aspartate Transaminase; COX-2; Cyclooxygenase-2; PGE2; Prostaglandin E2; WHO: World Health Organization;
Entamoeba histolytica is a cosmopolitan, parasitic protozoan of human large intestine, which is a causative agent of amoebiasis. Amoebiasis manifests with persistent diarrhea containing mucus or blood, accompanied by abdominal pain, flatulence, nausea and fever. In some cases amoebas may travel through the bloodstream from the intestine to the liver or to other organs, causing multiple abscesses. Amoebiasis is a dangerous, parasitic disease and after malaria the second cause of deaths related to parasitic infections worldwide. The highest rate of infections is observed among people living in or traveling through the tropics. Laboratory diagnosis of amoebiasis is quite difficult, comprising of microscopy and methods of molecular biology. Pathogenic species Entamoeba histolytica has to be differentiated from other nonpathogenic amoebas of the intestine, so called commensals, that very often live in the human large intestine and remain harmless. Other intestinal commensals are Entamoeba dispar and Entamoeba moshkovskii, morphologically the same as pathogenic species Entamoeba histolytica sensu stricto. The differential diagnosis of these three amoebas is possible with detection of their DNA.
Entamoeba histolytica (E. histolytica) is a unicellular organism of animal-parasitic infections, pathogenic protozoan from the family Entamoebidae. E. histolytica has identified and first described in literature by the doctor from St. Petersburg F. Aleksandrovich Lösch in 1875 . Entamoeba histolytica cause dangerous syndrome called amoebiasis (amoebosis). At this point it should be noted that the term amoebosis is reserved only for the disease caused by Entamoeba histolytica; that term cannot be used in cases of the infections of other amoebas species of the family Entamoebidae.
Amoebiasis in humans may take the intestinal or parenteral form. Intestinal amoebiasis (the most common) is manifested by increased diarrhea, abdominal pain, flatulence, gas and increased body temperature. In contrast, in situations when the amoeba enters through the blood from the intestines to other organs of the body, where it can form abscesses (such as the liver, lungs, brain), we are talking about parenteral amoebiasis.
Untreated amoebiasis (especially intestinal infestations) can result in even sloping death. World Health Organization (WHO) estimates that each year around the world close to 500 million people get sick, and 100 thousand people die because of amoebosis-induced infection dysentery .
E. histolytica belongs to the cosmopolitan parasites, occurring throughout the globe. Particularly exposed to this parasite are people living and traveling to the tropical and subtropical zones (Asia, Africa, India, Indonesia, Mexico, South America, South Africa). These zones climatic conditions are optimal for the Protozoan cysts, which described the external environment can survive for many days. This fact contributes to the increase in the number of infections slider Entamoeba histolytica amongst people in tropical zones. According to Weinke to high-risk groups who are particularly vulnerable to being infected by E. histolytica include men with a homosexual orientation . Prevalence, it means the incidence of infection is low in Poland and is about 1%, while in tropical countries can claim up to 50%. Most of the amoebiasis cases reported in Poland applies to people returning from a different climate zone and foreigners.
The digestive tract may be inhabited by several species of nonpathogenic amoebas in the family Entamoebidae, which include Entamoeba coli, Entamoeba hartmanni, Entamoeba polecki, Endolimax nana, Iodamoeba bűtschlii [4-6]. The aforementioned amoebas are so called commensals of colon, which may settle the intestinal mucosa physiologically not attracting damages. There are only isolated reports in the literature that some commensals may lead to pathogenic actions in the human large intestine. There have been a couple of cases of diarrhea problems caused by infections of Endolimax nana, Entamoeba polecki and I. bűtschlii in immunocompromised patients .
In 1925, Brumpt suggested that within the family Entamoebidae there are species Entamoeba dispar, which is morphologically identical with the pathogenic species Entamoeba histolytica . This fact is confirmed in subsequent studies by analyzing the genetic material of both protozoa, which turned out to be different [8-10]. The species Entamoeba dispar is nonpathogenic, and now it belongs to the commensals of the colon. It was found that Entamoeba dispar occurs together with Entamoeba histolytica in the same areas in the world .
Ali, Haque and Tanyuksel have reported that within the family Entamoebidae there is one species of amoeba, which is morphologically identical with Entamoeba histolytica and is so called Entamoeba moshkovskii. This species, like the Entamoeba dispar, is nonpathogenic for the man and also belongs to the commensals of the colon. Entamoeba moshkovskii is not cosmopolitan, the literature mentions that it is endemic in Bangladesh, North America and South Africa [6,11,12].
Nonpathogenic commensals of the colon should be necessarily vary with the species of pathogenic Entamoeba histolytica. This is of great importance from the point of view of pharmacotherapy, because the commensals of the colon usually do not require treatment.
The purpose and objectives of the study
In this work, efforts were made to present and systematize the most up-to-date information about the biology and pathogenicity of E. histolytica infection and symptoms of amoebiasis. However, special attention has been given to the broader subject of laboratory diagnosis of amoebiasis caused by Entamoeba histolytica. Discusses the usefulness, usability, and to reduce a number of analytical methods used in the diagnosis of various clinically as amoebiasis.
Biology and morphology of E. histolytica
Entamoeba histolytica can be found in the human body in the form such as infective cyst and vegetative form trophozoite.
Trophozoite: Trophozoite entity with a diameter equal to the 12-60µm, is surrounded by a three-tiered, lipid-protein cell membrane and creates characteristic ameboid pseudopodia that allow him to move and participate in phagocytosis, that is in the process of absorption of food particles. The cytoplasm is differentiated to ectoplasm and fine-grained endoplasm, which consists of cytosol and placed in him numerous cell organelles such as endosomes, lysosomes, Golgi apparatus, vacuoles with red blood cells and glycogen mass [2,4,5,13,14] . Trophozoite of Entamoeba histolytica does not contain mitochondria, which is why the energy distribution anaerobic wins the protozoans of glucose, which releases the stored glycogen mass [15,16]. A detailed process of all the metabolic pathways in the organism Entamoeba histolytica presented Loftus in the journal Nature .
Trophozoite of E. histolytica contains one round nucleus, in which the genetic material (DNA) concentrated in the form of a small, dense, centrally located karyosome and peripherally, evenly deployed chromatin. Presented to the construction of the cell nucleus is characteristic only of the species Entamoeba histolytica, as it has been shown that the protozoan in the family Entamoebidae is characterized by a high polymorphism of nuclei. The shape and position of the karyosome and the placement of chromatin in the cell nucleus is characteristic for each consecutive amoebas, which is used in their differential diagnosis. The structure of the nuclei of the amoebas is shown in Table 1.
Trophozoite is a form of this autonomic parasite, that is to say capable to perform all vital, including parasitic life in the body of the host. Trophozoite secretes specific proteolytic enzymes (e.g. hyaluronidase, cysteine proteinase) leading to degradation and cytolysis cells of tissues that have been attacked by E. histolytica . The image of the trophozoite is shown in Figure 1 .
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