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Entamoeba histolytica
Published in Peter D. Walzer, Robert M. Genta, Parasitic Infections in the Compromised Host, 2020
William A. Petri, Jonathan I. Ravdin
Entamoeba gingivalis trophozoites have a cytoplasm full of dark staining bodies and food vacuoles. E. gingivalis is associated with poor dental hygiene and must be distinguished from E. histolytica in the sputum of patients with lung abscess. Entamoeba histolytica trophozoites are large (12-60 μm), exhibit unidirectional motility, and can contain ingested erythrocytes. The cysts of E. histolytica contain up to four nuclei. The E. histolytica-like Laredo strain is nonpathogenic and grows optimally at 24°C in vitro, as opposed to an optimal growth temperature of 35°C for E. histolytica (14). Entamoeba hartmanni, formerly called the small race of E. histolytica, is a nonpathogenic commensal of identical morphology, but its trophozoite or cyst forms are smaller than those of E. histolytica (<12μm) (15). Entamoeba coli is frequently isolated together with E. histolytica in endemic areas in the tropics but is nonpathogenic. The trophozoites of E. coli never contain ingested erythrocytes, and their motility is more sluggish and less directed than that of E. histolytica. Entamoeba coli cysts contain up to eight nuclei (12,13). Entamoeba polecki infects pigs and monkeys in the tropics and has recently been associated with human disease in Upper Volta (16) and in Papua New Guinea. It is identified by its characteristics uninucleate cyst with a large karysome in the nucleus.
History of Amebiasis
Published in Roberto R. Kretschmer, Amebiasis: Infection and Disease by Entamoeba histolytica, 2020
In 1893 two German investigators, Quincke and Roos,21 clearly demonstrated the existence of amebas different from the E. dysenteriae known until then, some that even though they contained waste material in their interior, were ostensibly unable to phagocytize erythrocytes. They further demonstrated the inability of such amebas to induce tissue lesions. This latter species corresponds to the amebas nowadays called Entamoeba coli.
Nonhuman Parasites and Structures that Mimic Parasites
Published in Donald L. Price, Procedure Manual for the Diagnosis of Intestinal Parasites, 2017
In Plate 85, some structures that resemble protozoa when found in a fecal preparation are presented. White blood cells, especially neutrophils, may resemble cysts of amoebae because of the way the nucleus stains (Plate 85:1). Usually, these can be identified easily on wet preparations because of their irregular shape but they may be more difficult to identify on permanently stained fecal films. The object in Plate 85:2 appeared to be an amoeba when first seen on a wet preparation. When the cover glass was gently tapped, the object was seen as flat with what appears to be a nucleus superim posed on top. Pollen grains are very common during certain periods of the year (Plate 85:3,6) but can usually be identified (or at least not mistaken for parasites) because of their size and usual shape. Yeasts are very common in fecal specimens (Plate 85:5). Some yeast cells are 4 to 6 μm and may resemble oocysts of Cryptosporidia. The budding yeast cell immediately differentiates it from Cryptosporidia. Iodine will usually stain yeast cells but not Cryptosporidia. Acid-fast stains may be used to identify Cryptosporidia but there are some yeast cells that are also acid-fast. Care must be taken to use a stain and procedure that will differentiate between oocysts of Cryptosporidia and acid-fast yeast cells. A staining artifact (4) that was present on a permanently stained fecal film resembled cysts of Entamoeba coli as sometimes seen on trichromestained films, but on closer examination, it showed no internal structure.
Recruitment of feces donors among blood donors: Results from an observational cohort study
Published in Gut Microbes, 2018
Simon Mark Dahl Jørgensen, Christian Erikstrup, Khoa Manh Dinh, Lars Erik Lemming, Jens Frederik Dahlerup, Christian Lodberg Hvas
The evidence supporting the specific parts of the donor screening program is still limited. Currently, the screening guidelines focus on minimizing the potential risk of harm to the recipient. Importantly, we identified blood donors who were colonized with resistant bacterial species including ESBL-producing E. coli. We therefore suggest that tests for these microorganisms are included in future FMT screening programs. We also found that donors who tested positive for intestinal pathogens harbored a variety of different asymptomatic viruses, bacteria, and parasites. Our most common finding in the fecal screening was Entamoeba coli, and despite its apathogenic nature, donors who tested positive were excluded as a precaution. Notably, controversy exists to whether certain protozoa such as Blastocystis species may be more prevalent in healthy individuals and linked to certain beneficial health indices.22,23 For now, however, our data are consistent with the findings of diverse pathogens reported by others14,15 and support the current broad-spectrum screening approach for pathogens.
Comparing the efficiency of four diagnostic concentration techniques performed on the same group of intestinal parasites
Published in Alexandria Journal of Medicine, 2018
Kamran Pakdad, Seyed Dawood Mousavi Nasab, Fatemeh-Alsadat Damraj, Nayeb Ali Ahmadi
For the detection of Entamoeba coli, the FEC and all other three techniques revealed substantial agreement (𝜅 value above 60%, P = .000), but the corresponding agreement value for Giardia lamblia was found only between the FEC and FGC techniques (Table 4; κ = 0.614, P ≤ .001).