China
Africa
Explore chapters and articles related to this topic
Entamoeba histolytica
Published in Peter D. Walzer, Robert M. Genta, Parasitic Infections in the Compromised Host, 2020
William A. Petri, Jonathan I. Ravdin
Dientamoeba fragilis, named for its susceptibility to osmotic lysis, has not been recognized to have a cyst form. The trophozoites are small (5-12/μm), have active motility, and characteristically have four to eight chromatin granules in the one or two nuclei present. Although originally thought not to be pathogenic, it is increasingly being recognized as a cause of prolonged (17) or inflammatory (18) diarrhea. Endolimax nana and lodamoeba butschlii are both nonpathogenic commensals. Endolimax nana trophozoites are small (6-15μm), move sluggishly, and have a single nucleus containing a large central karyosome; the cyst form contains four nuclei (12,13). Iodamoeba butschlii trophozoites are small (6-20 μm), with sluggish movement; the cyst form is easily identified by its large glycogen vacuole, which stains with iodine (12,13).
The Protozoa
Published in Donald L. Price, Procedure Manual for the Diagnosis of Intestinal Parasites, 2017
B. hominis has been reported as the cause of diarrhea in immunodeficient patients (Zierdt, 1991a,b) but it is also present in the intestine of many apparently healthy individuals. The usual forms seen in fecal preparations are shown in the diagrams (Plate 41:1,2,5). They vary greatly in size from about 5 to 30 μm in diameter, have a large central area that has the appearance of a vacuole, and an outer ring of cytoplasm. Several pale-staining nuclei are embedded in the cytoplasm along with darker bodies referred to as volutin. Because their refractive index is similar to that of intestinal amoebae, some forms may be mistaken for Endolimax nana or other cysts of amoebae (Plate 41:3). Others are dense, thick walled, and have a darkly staining central area (Plate 41:4). Blastocystis divides by binary fission (Plate 41:6).
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].