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 Table of Contents  
Year : 2014  |  Volume : 4  |  Issue : 2  |  Page : 96-98  

Entamoeba bangladeshi: An insight

Department of Medicine, School of Medicine, University of Virginia, Charlottesville, Virginia, USA

Date of Acceptance29-Jul-2014
Date of Web Publication12-Aug-2014

Correspondence Address:
Carol A Gilchrist
Department of Medicine, School of Medicine, University of Virginia, Charlottesville, Virginia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2229-5070.138536

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Molecular tools have the potential to differentiate microscopically similar gut micro-eukaryotes that may have significantly different relationships with the human host. Using broad range Entamoeba primers to amplify a section of the eukaryotic 18S small subunit ribosomal RNA gene a novel member of the Entamoeba family (Entamoeba bangladeshi) has recently been identified. The goal of this review is to place this species in the context of what is already known about this genus and to discuss the tools and data needed to elucidate the host-microbe relationship.

Keywords: Entamoeba bangladeshi, Entamoeba dispar, Entamoeba histolytica, Entamoeba moshkovskii, Protozoa

How to cite this article:
Gilchrist CA. Entamoeba bangladeshi: An insight. Trop Parasitol 2014;4:96-8

How to cite this URL:
Gilchrist CA. Entamoeba bangladeshi: An insight. Trop Parasitol [serial online] 2014 [cited 2022 Dec 3];4:96-8. Available from: https://www.tropicalparasitology.org/text.asp?2014/4/2/96/138536

   Introduction Top

The Entamoeba genus branched early from the main eukaryotic lineages at some point however it began to exploit the ecological niche provided by the metazoan gut. Protozoan cysts have been isolated from the fossilized fecal material of dinosaurs, and current molecular methods have led to the identification of Entamoeba species in a wide range of vertebrates. [1],[2] Adaption to the anerobic gut environment has resulted in the secondary loss of the capacity to metabolize oxygen [3] and some, but not all Entamoeba species have adopted a parasitic lifestyle and cause host disease. Entamoeba histolytica the causative agent of amebaisis in humans and a major cause of morbidity and mortality in children under five has for this reason been the focus of the most study. [4],[5] Evidence is now building however that the second member of the Entamoeba genus Entamoeba moshkovskii is also associated with human disease. [6],[7]

An ongoing longitudinal study of enteric diseases common in a disadvantaged Bangladesh community provided the ideal opportunity to examine the diversity of commensal and parasitic Entamoeba species occurring in children at that geographical location. [8],[9],[10],[11] The study involved the routine microscopic characterization of surveillance and diarrheal stool for Entamoeba cysts and the deployment of molecular tools to distinguish the species known to infect humans at this geographical location (E. histoytica, Entamoeba dispar and E. moshkovskii). This work, therefore, resulted in a pool of samples known to contain cysts morphologically identical to E. histolytica but which were molecularly distinct. [10]

   Entamoeba bangladeshi Top

Despite the advances in the specificity and sensitivity of molecular diagnostic methods to detect known pathogens the cause of many diarrheal illnesses in children can often not be identified. [12],[13],[14] Despite the well-known limitations of microscopy as a diagnostic tool for E. histolytica its affordability and accessibility has resulted in its continued use. [15],[16],[17] Microscopic analysis of both surveillance and diarrheal stool specimens identified samples, which contained cyst and trophozoites indistinguishable from E. histolytica, but which were clearly differentiated from known Entamoeba species by immuno- and DNA based-diagnostic tests. [10] The initial focus of the work of Royer et al. was to discover new Entamoeba species in these samples, which could potentially be pathogenic. [10]

   Microscopic and phylogenetic analysis Top

As described above cysts and trophozoites from the selected fecal samples appeared similar to those of E. histolytica by light microscopy. The amoeboid trophozoites of the novel isolates were cultured from positive stool samples by standard techniques and examined by transmission electron microscopy. This technique revealed no additional features (such as the hydrogenosomes present in the amoeboid Dientamoeba fragilis) which would allow Entamoeba bangladeshi to be distinguished visually from other members of the Entamoeba genus. [10],[18],[19] Primers directed against a small subunit rRNA region conserved throughout the Entamoeba family were used to amplify a variable section of the gene, and its sequence confirmed that E. bangladeshi was a novel species that was most similar to the other members of the Entamoeba family, which infect humans, E. histolytica and E. dispar. [10],[20]

   Virulence characteristics Top

Children in this study location are constantly exposed to enteric pathogens, and identification of stool samples with multiple parasites are common even during routine surveillance suggesting that a sub-clinical disease is common. [14] E. bangladeshi has been isolated from the stools of both asymptomatic children and those experiencing diarrhea. Additional clinical and epidemiological studies such as those that linked the E. moshkovskii species with human disease are needed to discern the true role of E. bangladeshi in the human host. [6],[21] New avenues for exploration of the role this micro-eukaryote may play in human health have been discovered during the recent massive parallel sequencing studies of human gut microbiota. It is unknown at present what (if any) subtle impact of colonization with E. bangladeshi could have on human gut flora and the intestinal immune system. [22] Microbial organisms previously regarded as commensal passengers in the human intestine have been found to impact immune homeostasis-leading to the view that the commensal gut microbial community is a "virtual organ," which can have large effects on host well-being. [23],[24] The two known pathogenic Entamoeba species despite being present in very low copy numbers in the human gut obviously can have a drastic effect on the indigenous microflora as they cause diarrheal illness. [25] It is intriguing to speculate that other Entamoeba species which do not cause clinical disease may still have a large impact on microflora composition. [26]

   Protective immunity Top

Current evidence suggests that short term mucosal immunity develops in response to Entamoeba infections. [27],[28] However this protection is species-specific with little or no protection conferred by infections with members of the different species and co-infections are common. [29] Antibodies based on the immunodominant Gal/GalNAc lectin of E. histolytica were unable to recognize E. bangladeshi positive samples in immunodiagnostic ELISA assays. [10] It is therefore unlikely that an infection with E. bangladeshi although it may confer for a limited period protection against recolonization with itself will offer any protection against succeeding pathogenic E. histolytica or E. moshkovskii infections.

   Conclusion Top

Molecular characterization of E. bangladeshi is necessary to appreciate the ecological niche it occupies in human health and disease. Sequencing of E. bangladeshi and E. histolytica isolates is needed to evaluate the natural diversity of this species in this genus. Finally new tools are needed to rapidly identify this species for high-throughput epidemiologic studies in humans and to determine the host range and environmental reservoirs of this potential parasite.

   References Top

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2.Stensvold CR, Lebbad M, Verweij JJ, Jespersgaard C, von Samson-Himmelstjerna G, Nielsen SS, et al. Identification and delineation of members of the Entamoeba complex by pyrosequencing. Mol Cell Probes 2010;24:403-6.  Back to cited text no. 2
3.Clark CG, Roger AJ. Direct evidence for secondary loss of mitochondria in Entamoeba histolytica. Proc Natl Acad Sci U S A 1995;92:6518-21.  Back to cited text no. 3
4.Haque R, Huston CD, Hughes M, Houpt E, Petri WA Jr. Amebiasis. N Engl J Med 2003;348:1565-73.  Back to cited text no. 4
5.Kotloff KL, Nataro JP, Blackwelder WC, Nasrin D, Farag TH, Panchalingam S, et al. Burden and aetiology of diarrhoeal disease in infants and young children in developing countries (the Global Enteric Multicenter Study, GEMS): A prospective, case-control study. Lancet 2013;382:209-22.  Back to cited text no. 5
6.Shimokawa C, Kabir M, Taniuchi M, Mondal D, Kobayashi S, Ali IK, et al. Entamoeba moshkovskii is associated with diarrhea in infants and causes diarrhea and colitis in mice. J Infect Dis 2012;206:744-51.  Back to cited text no. 6
7.Ali IK, Hossain MB, Roy S, Ayeh-Kumi PF, Petri WA Jr, Haque R, et al. Entamoeba moshkovskii infections in children, Bangladesh. Emerg Infect Dis 2003;9:580-4.  Back to cited text no. 7
8.Mondal D, Minak J, Alam M, Liu Y, Dai J, Korpe P, et al. Contribution of enteric infection, altered intestinal barrier function, and maternal malnutrition to infant malnutrition in Bangladesh. Clin Infect Dis 2012;54:185-92.  Back to cited text no. 8
9.Korpe PS, Liu Y, Siddique A, Kabir M, Ralston K, Ma JZ, et al. Breast milk parasite-specific antibodies and protection from amebiasis and cryptosporidiosis in Bangladeshi infants: A prospective cohort study. Clin Infect Dis 2013;56:988-92.  Back to cited text no. 9
10.Royer TL, Gilchrist C, Kabir M, Arju T, Ralston KS, Haque R, et al. Entamoeba bangladeshi nov. sp. Bangladesh. Emerg Infect Dis 2012;18:1543-5.  Back to cited text no. 10
11.Gilchrist CA, Ali IK, Kabir M, Alam F, Scherbakova S, Ferlanti E, et al. A Multilocus Sequence Typing System (MLST) reveals a high level of diversity and a genetic component to Entamoeba histolytica virulence. BMC Microbiol 2012;12:151.  Back to cited text no. 11
12.Korpe PS, Stott BR, Nazib F, Kabir M, Haque R, Herbein JF, et al. Evaluation of a rapid point-of-care fecal antigen detection test for Entamoeba histolytica. Am J Trop Med Hyg 2012;86:980-1.  Back to cited text no. 12
13.Liu J, Kabir F, Manneh J, Lertsethtakarn P, Begum S, Gratz J, et al. Development and assessment of molecular diagnostic tests for 15 enteropathogens causing childhood diarrhoea: A multicentre study. Lancet Infect Dis 2014; 14:716-24.  Back to cited text no. 13
14.Taniuchi M, Sobuz SU, Begum S, Platts-Mills JA, Liu J, Yang Z, et al. Etiology of diarrhea in Bangladeshi infants in the first year of life analyzed using molecular methods. J Infect Dis 2013;208:1794-802.  Back to cited text no. 14
15.Taniuchi M, Verweij JJ, Noor Z, Sobuz SU, van Lieshout L, Petri WA, et al. High throughput multiplex PCR and probe-based detection with Luminex beads for seven intestinal parasites. Am J Trop Med Hyg 2011;84:332-7.  Back to cited text no. 15
16.Haque R, Mondal D, Karim A, Molla IH, Rahim A, Faruque AS, et al. Prospective case-control study of the association between common enteric protozoal parasites and diarrhea in Bangladesh. Clin Infect Dis 2009;48:1191-7.  Back to cited text no. 16
17.den Hartog J, Rosenbaum L, Wood Z, Burt D, Petri WA Jr. Diagnosis of multiple enteric protozoan infections by enzyme-linked immunosorbent assay in the Guatemalan highlands. Am J Trop Med Hyg 2013;88:167-71.  Back to cited text no. 17
18.Camp RR, Mattern CF, Honigberg BM. Study of Dientamoeba fragilis Jepps and amp; Dobell. I. Electronmicroscopic observations of the binucleate stages. II. Taxonomic position and revision of the genus. J Protozool 1974;21:69-82.  Back to cited text no. 18
19.Banik GR, Birch D, Stark D, Ellis JT. A microscopic description and ultrastructural characterisation of Dientamoeba fragilis: An emerging cause of human enteric disease. Int J Parasitol 2012;42:139-53.  Back to cited text no. 19
20.Stensvold CR, Lebbad M, Victory EL, Verweij JJ, Tannich E, Alfellani M, et al. Increased sampling reveals novel lineages of Entamoeba: Consequences of genetic diversity and host specificity for taxonomy and molecular detection. Protist 2011;162:525-41.  Back to cited text no. 20
21.Tachibana H, Yanagi T, Akatsuka A, Kobayashi S, Kanbara H, Tsutsumi V. Isolation and characterization of a potentially virulent species Entamoeba nuttalli from captive Japanese macaques. Parasitology 2009;136:1169-77.  Back to cited text no. 21
22.Elinav E, Henao-Mejia J, Flavell RA. Integrative inflammasome activity in the regulation of intestinal mucosal immune responses. Mucosal Immunol 2013;6:4-13.  Back to cited text no. 22
23.Evans JM, Morris LS, Marchesi JR. The gut microbiome: The role of a virtual organ in the endocrinology of the host. J Endocrinol 2013;218:R37-47.  Back to cited text no. 23
24.Subramanian S, Huq S, Yatsunenko T, Haque R, Mahfuz M, Alam MA, et al. Persistent gut microbiota immaturity in malnourished Bangladeshi children. Nature 2014;510:417-21.  Back to cited text no. 24
25.Colgan MT. The bacterial flora of the intestinal tract: Changes in diarrheal disease and following antimicrobial therapy. J Pediatr 1956;49:214-28.  Back to cited text no. 25
26.Everard A, Matamoros S, Geurts L, Delzenne NM, Cani PD. Saccharomyces boulardii administration changes gut microbiota and reduces hepatic steatosis, low-grade inflammation, and fat mass in obese and type 2 diabetic db/db mice. MBio 2014;5:e01011-14.  Back to cited text no. 26
27.Haque R, Mondal D, Duggal P, Kabir M, Roy S, Farr BM, et al. Entamoeba histolytica infection in children and protection from subsequent amebiasis. Infect Immun 2006;74:904-9.  Back to cited text no. 27
28.Abd-Alla MD, Jackson TF, Rogers T, Reddy S, Ravdin JI. Mucosal immunity to asymptomatic Entamoeba histolytica and Entamoeba dispar infection is associated with a peak intestinal anti-lectin immunoglobulin A antibody response. Infect Immun 2006;74:3897-903.  Back to cited text no. 28
29.Shimokawa C, Culleton R, Imai T, Suzue K, Hirai M, Taniguchi T, et al. Species-specific immunity induced by infection with Entamoeba histolytica and Entamoeba moshkovskii in mice. PLoS One 2013;8:e82025.  Back to cited text no. 29

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