Symptomatic Entamoeba dispar Infections Among Men Who Have Sex With Men, New York City, 2018
Kimberly MergenLisa AlleyneRobert FitzhenryRajitha SunkaraBruce GuteliusAmy K. AldermanMichelle C. DickinsonEmily McGibbonCorinne N. ThompsonSusan Madison‐Antenucci
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Abstract Entamoeba histolytica is considered the primary species causing the parasitic gastrointestinal infection amebiasis. A cluster of amebiasis infections was identified in 2018 among men who have sex with men in New York City and was likely caused by Entamoeba dispar, traditionally considered to be nonpathogenic.Keywords:
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Amoebiasis
Entamoeba
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Evolution of experimental hepatic lesions produced in hamsters with Entamoeba histolytica and E. dispar was evaluated quantitatively and qualitatively through morphometry and immunohistochemistry. Animals infected with E. dispar developed hepatic lesions quantitatively and qualitatively similar to those produced by E. histolytica on the first three days of infection. On the 6th and 8th days of infection, E. histolytica produced larger tissue damage than E. dispar. A gradual decrease was observed in the number of trophozoites along the infection. A negative correlation was observed between the reduced number of trophozoites and the larger area of necrosis in both groups, confirming the importance of trophozoites killed in the lesion genesis. Regarding the genetic similarity between E. histolytica and E. dispar, comparison strategy between lesions produced by these species may culminate in identifying virulence factors of E. histolytica.
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Amebiasis is a disease caused by the protozoan parasite Entamoeba histolytica. This ameba can colonize the human intestine and persist as a commensal parasite, similar to Entamoeba dispar, an ameba considered to be non-pathogenic. The similarities between E. histolytica and E. dispar make the latter an attractive model for studies aimed at clarifying the pathogenesis of amebiasis. However, in addition to being an interesting experimental model, this relative of E. histolytica remains poorly understood. In the 1990, it was believed that E. dispar was unable to produce significant experimental lesions. This scenario began to change in 1996, when E. dispar strains were isolated from symptomatic patients in Brazil. These strains were able to produce liver and intestinal lesions that were occasionally indistinguishable from those produced by E. histolytica. These and other findings, such as the detection of E. dispar DNA sequences in samples from patients with amebic liver abscess, have revived the possibility that this species can produce lesions in humans. The present paper presents a series of studies on E. dispar that begin to reveal a new facet of this protozoan.
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Differentiation of invasive strains of Entamoeba histolytica according to their pathogenicity has been a topic of long debate, but now the pathogenic species only is regarded as E. histolytica while the non pathogenic species is E. dispar. The present study applied immunoblot to differentiate infections of the two species among microscopically-detected cyst-passers in Korea. The crude extract of E. histolytica separated in 5.20% gradient gels, revealed many fractions of 94, 81, 71, 50, 44, 38.5, 37.5, 29, 19, and 18 kDa when the cysteine proteinase inhibitor, E64, was supplemented. The scrum IgG antibody of 3 proven E, histolytica cases reacted with the antigenic fractions of 117, 110, 99, 68, 66, 60, 54, 52, 46, and 45 kDa. Sera of PCR confirmed 3 cases of E. dispar reacted only to the 117 kDa fraction of the E. histolytica crude extract which was regarded as non-specific. To the antigen of monoxenic E. dispar, sera of E. dispar and E. histolytica cases showed the same immunoblot reactions. The serum IgA antibody reacted with several antigenic fractions of both E. histolytica and E. dispar, but IgM and IgE antibodies showed no reaction to either antigen. Sera of 24 symptomless amebic cyst passers were screened with the E. histolytica antigen; two were found to be infected by E. histolytica and 22 were by E. dispar. The present findings suggest that in Korea most of asymptomatic cyst passers of E. histolytica are carriers of E. dispar. Immunoblot using E. histolytica antigen is a good technique for the differentiation of E. histolytica and E. dispar infections.
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In an effort to improve the diagnosis of intestinal amoebiasis, a real-time PCR has been used for the detection and differentiation of Entamoeba histolytica and E. dispar infections in African or South American immigrants who live in Spain. Faecal samples from all of the 130 subjects had apparently been found to contain E. histolytica/E. dispar cysts by microscopical examination. Using the real-time PCR, E. histolytica DNA was detected in faecal samples from only 10 (7.7%) of the immigrants, with E. dispar DNA detected in the samples from another 117 (90.0%) of the subjects. The use of such PCR in the routine investigation of patients found positive for E. histolytica/E. dispar cysts (by microscopy) is recommended, especially in non-endemic areas.
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Amoebiasis
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Current diagnosis of Entamoeba histolytica infection requires the direct microscopic identification of the parasite, a technique that is insensitive and cannot distinguish pathogenic E. histolytica from noninvasive E. dispar. Enzyme-linked immunosorbent assay (ELISA) antigen detection tests were developed to distinguish E. histolytica from E. dispar infection in stool specimens. The ELISA result for E. histolytica antigen was positive in 26 of 27 E. histolytica-positive stool specimens, three of 25 E. dispar-positive stools, and one of 30 stools with other or no intestinal parasites, giving a specificity and sensitivity for the detection of E. histolytica infection of 93% and 96%, respectively. The assay result used to detect both E. dispar and E. histolytica was positive in 26 of 27 E. histolytica-positive stools, 19 of 25 E. dispar-positive stools, and one of 30 stools negative by microscopy and culture for Entamoeba, giving a specificity and sensitivity of 97% and 87%, respectively. Because these ELISAs can be completed in several hours, they offer promise as rapid and sensitive means of detecting amebic infection.
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Entamoeba
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Amibias are illness in Tunisia diagnosed until now on the sole basis of the morphological aspects of the parasite. Our aim is to report the first Tunisian results concerning the molecular identification of E. histolytica/E. dispar,25 stools presenting cysts and/or vegetative shapes of E. histolytica/E. dispar were gathered at the "Laboratoire de Parasitologie Hôpital La Rabta Tunis" between 2001and 2004 for PCR. The stools came from 24 subjects, one of them having two samples: 9 Tunisian patients, 5 adressed to the hospital services for abdominal pains or diarrheas and 4 adressed for a systemic tracking (food manipulation), and 15 foreign students for which a tracking is done each fall.The identification showed thus for the Tunisian patients the presence of : E. histolytica alone for a patient (food manipulator) 11%. E. histolytica associated to E. dispar for two patients 22%. E. dispar alone for six patients 67%. Nearly similar results has been obtained for foreign student's samples: E. histolytica alone in one case (7%), E. histolytica associated to E. dispar in four cases (26%) and E. dispar alone in 10 cases (67%).These results show therefore the existence in Tunisia the two species E. histolytica and E. dispar for symptomatic or non symptomatic patients. The distinction between the two species is very important on the therapeutic level as well as the epidemiologic and public health level.
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The purpose of the study was to obtain more reliable epidemiological data concerning Entamoeba (E.) histolytica infection in Tunisian food handlers using established molecular tools able to differentiate E. histolytica from E. dispar. From 2002 to 2005, 4,266 fresh stools specimens received in the setting of the National program of food handlers' control were analysed by optical microscopy. Twelve (2.8 ‰) were positive for the presence of four nuclei cysts identified as E. histolytica/E. dispar. Extraction of DNA from the 12 samples, followed by specific amplifications of E. histolytica and E. dispar SSU rDNA, showed that 11 samples (92%) were positive for E. dispar and negative for E. histolytica. Sequencing analysis of 8 PCR products permitted to verify the results obtained with conventional PCR. The remaining sample was negative by PCR amplifying E. histolytica DNA or E. dispar DNA specifically, although it did not show any inhibition. It probably contains protozoan cysts genetically distinct from these two species but morphological similar. Estimation of relative proportions between E. histolytica and E. dispar in cyst carriers showed that all explored individuals harboured the non pathogenic E. dispar strains. This result highlights the need of use in this population of complementary tests that allow specific diagnosis and obviate unnecessary chemotherapy.
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In the Czech Republic, 40 to 50 cases of Entamoeba histolytica/dispar infections are reported annually to the National Reference Laboratory for diagnostics of intestinal parasitoses. However, the actual number of patients with Entamoeba histolytica infection is unknown as diagnosis relies on cyst detection in faecal samples by microscopy, the method which cannot differentiate between pathogenic E. histolytica and nonpathogenic E. dispar. The aim of this study was (1) to evaluate the proportions between E.histolytica and E. dispar in patients, mainly travellers, using multiplex nested PCR technique, (2) to evaluate specificity of the technique for detection of these species.Faecal samples from 68 patients microscopically positive for cysts of E. histolytica/dispar were tested by PCR. Of these, 65 persons (95.6%) were positive for E. dispar, whereas only 3 patients (4.4%) were positive for E. histolytica.This study shows that the number of patients infected with pathogenic E. histolytica is very low in the Czech Republic and points to the necessity of differentiation of Entamoeba species for physician's decision in treatment of E. histolvtica- or E.dispar-infected persons.
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Entamoeba
Chitinase
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