Entamoeba Species Commonly Diagnosed as Entamoeba Histolytica and Enteric Bacteria in the Pathogenesis of Diarrhea in Addis Ababa.
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Date
2007-08-05
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Addis Ababa University
Abstract
Clinical reports relying on microscopic diagnosis give an impression that intestinal amoebiasis is
very common in Ethiopia. However, recent species specific PCR-based method had shown little
or no true infection with Entamoeba histolytica. The present study was conducted to assess the
association of diarrheagenic bacteria vis-à-vis the Entamoeba trophozoites commonly diagnosed
as E. histolytica in diarrheal patients. One hundred and fifty diarrheal patients from Selam Health
Center in Gulelie Sub-city and Addis Ketema Propride Clinic in Addis Ababa were recruited in a
study conducted between December 2005 and April 2006. Single stool samples were collected
from the study participants, and inspected macroscopically for consistency, appearance, and the
presence of gross blood. Wet mount of the stool samples was made to detect the presence of fecal
leukocytes and red blood cells (RBCs), E. histolytica/E. dispar trophozoites and other intestinal
parasites. The specimens were further tested for the presence of E. histolytica/E. dispar DNA by
PCR; for stool antigens of E. histolytica by antigen ELISA; and by stool culture for dirrheagenic
bacteria. Microscopic observations revealed E. histolytica/E. dispar to be the most common
parasite diagnosed (40.7% of the diarrheic patients) followed by Blastocytis hominis (24.7%) and
Giardia lamblia (12.7%). However, the PCR based method which amplifies short tandem
repeating gene sequence on the tRNA confirmed only 10 cases (16.4%) of E. histolytica/E.
dispar. Out of these only two (3.3%) were the pathogenic E. histolytica .The Entamoeba specific
stool antigen ELISA detected 30 cases (20%) to be E. histolytica /E. dispar. However, only two
of the ELISA positive cases were confirmed by the PCR based method. Of the 150 diarrheal
patients, 57(38%) were Shigellae and 1(0.4%) Escherichia coli B. Infection with trophozoites of
Entamoeba species showed no clear association with clinical symptoms such as history of
bloody-mucoid stools, history of low-grade fever, and microscopic finding of pus cells and
RBCs(P>0.05). On the other hand, the isolation of Shigellae in patients with these clinical
symptoms was significantly higher (P<0.05). High rate of co-infection in patients with
trophozoites of Entamoeba spp. were observed most commonly with Shigella spp. (41.3%),
Blastocystis hominis (32.8%), Giardia lamblia (14.8%). Consistent with the previous reports,
the present study indicated the rare occurrence of E. histolytica in Ethiopia and the inadequacy of
microscopy for diagnosis of amoebiasis. The finding in this study reinforces the suggestion that
patients with enteric bacterial pathogens may be wrongly diagnosed as suffering from amoebiasis
simply due to the presence of non-pathogenic amoeba trophozoites in their stools. However, the
contribution of enteric coccidians, like Cryptosporidium parvum, Isospora belli, and
Microsporidia must also be assessed to more correctly establish the etiologyof diarrhea in
Ethiopia.
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Keywords
Entamoeba Histolytica, E. Dispar, Entreic Bacteria, Co-Infection, PCR, ELISA