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Infections
Published in C. Simon Herrington, Muir's Textbook of Pathology, 2020
Entamoeba dispar may be asymptomatic, or a cause of mild lower gut diarrhoea. It is commonly identified in homosexual men. Conversely, E. histolytica is potentially fatal, causing painful diarrhoea with blood in the stool; this mimics idiopathic inflammatory bowel diseases such as ulcerative colitis and Crohn's disease, and bacterial colitis. This may resolve spontaneously, or persist and progress to more severe mucosal ulceration. If untreated, up to 5% of patients – and especially those who are pregnant or receiving steroids – suffer colon perforation and peritonitis, which has a high mortality.
Entamoeba histolytica
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Jesús Serrano-Luna, Moisés Martínez-Castillo, Nidia Leon-Sicairos, Mineko Shibayama, Mireya de la Garza
Emil Brumpt first proposed a classification of human Entamoeba into two distinct species in 1925. The amoeba associated with diarrhea symptoms with or without dysentery was designated E. histolytica, and the amoeba for asymptomatic individuals was coined Entamoeba dispar.11 This grouping was further complicated during the Second World War when Entamoeba moshkovskii was reported as a free-living amoeba in the 1940s,12 and subsequently found in clinical cases involving children in Bangladesh,13,14 as well as in individuals from developed countries.12 Specific antibodies (Abs), isoenzyme patterns, and DNA hybridization tests have been employed to identify the different species of Entamoeba.15–20 From such findings, the original Brumpt proposal was confirmed, and E. dispar has since been universally accepted.21
Diloxanide Furoate
Published in M. Lindsay Grayson, Sara E. Cosgrove, Suzanne M. Crowe, M. Lindsay Grayson, William Hope, James S. McCarthy, John Mills, Johan W. Mouton, David L. Paterson, Kucers’ The Use of Antibiotics, 2017
Jared E. Eisemann, Paul M. Griffin
Diloxanide furoate is active against the protozoan parasite E. histolytica within the intestinal lumen. It is used for treating asymptomatic (or only mildly symptomatic) patients passing cysts. Patients should ideally be confirmed to be infected with E. histolytica rather than the morphologically identical but nonpathogenic ameba species Entamoeba dispar or Entamoeba moshkovskii (Knight, 1980; WHO/PAHO/UNESCO, 1997; Haque et al., 2003; Ayed et al., 2008). The drug is not effective in patients with invasive amebic colitis and is of no value in treating extraintestinal amebiasis because it has little or no activity outside the intestinal lumen (Botero, 1964). Diloxanide furoate has been shown in vitro to have little or no effect on other intestinal protozoan parasites including Dientamoeba fragilis (Nagata et al., 2012) and Blastocystis hominis (Zierdt et al., 1983).
Validation and maintaining laboratory developed molecular tests compliant with ISO15189 for diagnosis of intestinal parasitic infections
Published in Expert Review of Molecular Diagnostics, 2022
Description of performance characteristics for NAATs in our setting, the way of testing, and criteria are summarized in Table 1. The genetic target used in a particular assay is the basis of its performance and are described with ‘in-silico sensitivity’ and ‘in-silico specificity.’ Basic knowledge of the target organism, existence of variants, genotypes, species, and subspecies but also the historic taxonomy and nomenclature is needed to select sequences from the GenBank and other resources of different genetic variants. For example older Entamoeba dispar sequence submissions in the GenBank could still be listed belonging to Entamoeba histolytica at best mentioned in the description as nonpathogenic strain of E. histolytica [7].
An audit of inpatient stool ova and parasite (O&P) testing in a multi-hospital health system
Published in Journal of Community Hospital Internal Medicine Perspectives, 2020
Mohammad Qasim Khan, Nicole Gentile, Ying Zhou, Becky A. Smith, Richard B. Thomson, Eugene F. Yen
As seen in our study, Blastocystisspp. represents the most frequently isolated parasites on O&P exams in the US. However, the commonest parasitic causes of infectious diarrhea in the US are Giardia duodenalis, Entamoeba histolytica/Entamoeba dispar, and Cryptosporidium species [7,9–11]. There is currently a debate regarding whether Blastocystisspp. are intestinal commensals, true pathogens, or markers of dysbiosis. There are few observational studies and animal models suggesting a direct relationship between Blastocystis infection and disease [12–14]. On the contrary, several studies have shown no correlation between Blastocystisspp. and symptoms [15,16]. Interestingly, Blastocystisspp. has been found in stool samples in association with other potential pathogens, leading some reports to infer that in patients with Blastocystisspp. in their stools, another pathogen may be identified on further examination. In our study, across the entire 3-year duration, only one stool sample revealed a second identifiable organism in addition to Blastocystisspp. and that too of Endolimax nana, a non-pathogenic intestinal commensal. Given conflicting studies with regards to its pathogenicity, there are currently no consensus guidelines on the treatment of Blastocystis infection. Some authors assert that treatment can be considered if symptoms are present and if more than 5 cysts per high-power field are seen on stool microscopy [17]. It should be noted however that the association between parasite concentration and symptoms is also under contention [18–20].
British Journal of Biomedical Science in 2018: what have we learned?
Published in British Journal of Biomedical Science, 2019
Helicobacter pylori is an important and common pathogen [27,38]. Yakoob and colleagues [39] studied the link between this organism and common protozoal parasites in 161 patients with abdominal discomfort and chronic diarrhoea compared to 114 age and sex matched controls. Stool samples were examined by microscopy and DNA extracted for PCR with specific primers for H. pylori and protozoal parasites Blastocystis sp., Entamoeba sp. (Entamoeba histolytica, Entamoeba dispar and Entamoeba moshkovskii) and Giardia duodenalis (G. duodenalis). Patients with diarrhoea were more likely to be infected with Blastocystis sp. (P < 0.001), E. histolytica (P = 0.027) and E. moshkovskii (P = 0.003). There was no difference in the frequency of H. pylori (P = 0.528), G. duodenalis (P = 0.697) or E. dispar (P = 0.425). Thirty-three patients and 27 controls had H. pylori infection. Of these, 22 patients and 6 controls were infected with Blastocystis sp. (P = 0.001), 6 patients and no controls with E. histolytica (P = 0.02), and 7 patients and 9 controls with E. dispar (P = 0.292). The authors conclude that diarrhoea is linked to infection with Blastocystis and Entamoeba sp., whilst in H. pylori infection, diarrhoea is linked to Blastocystis sp. and E. histolytica infection. These associations may be linked pathogenically.