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A 56-year-old man with half of year history of UC was admitted to our hospital due to abdominal pain, diarrhea, and hematochezia (more than ten times per day) for two weeks. He had had homosexual intercourse with many men. Subsequent laboratory findings revealed that there was a significant increase in elevated white blood cells (WBC, 11.77x109/L), C-Reactive Protein (CRP, 83.7 mg/L), tumor necrosis factor-alpha (TNF-ɑ, 6.83 pg/ml), interleukin-2 (IL-2, 75.78 pg/ml), IL-6 (124.68 pg/ml), IL-10 (58.24 pg/ml) and IL-17 (128.76 pg/ml), and fecal calprotectin (FC >1800 μg/g). Albumin (ALB, 22.5 g/L) and Hemoglobin (Hb, 98 g/L) were significantly decreased. Amoeba was identified in the stool. The abdominal contrast-enhanced Computed Tomography (CT) showed that there was thickened intestinal wall in the sigmoid colon and rectum. Colonoscopy and intestinal histopathology suggested active severe UC (E2) and Entamoeba Histolytica (trophozoites) in the necrotic tissue (Figure 1). The result of enzyme immunoassay (EIA) screening for HIV was positive. The HIV viral load was 7.85x109 copies/mL, and the CD4+ cell count was 43/μL.

Aims: This study evaluates the action of Weissella paramesenteroides WpK4 on amoebic colitis., Methods and Results: Weissella paramesenteroides WpK4 was administered in Entamoeba dispar infected and noninfected mice and clinical parameters were evaluated. Following 7 days, the caeca were collected for histopathology, morphometry and immunohistochemical staining of MUC-2, CDC-47 and IgA. The treatment reduced diarrhoea and the presence of blood in the faeces and diminished the area of necrosis, also causing weight gain. Also, the addition of this bacterium enhanced the expression of the mucin (MUC-2). The reduction in necrosis and increased CDC-47 expression indicates significant epithelial regeneration. The negative correlation between CDC-47 and the necrosis area reveals that the bacterium favoured the recovery of the necrotic regions and the positive correlation found between the expression of MUC-2 and CDC-47 indicates that the epithelial regeneration also supports the synthesis of MUC-2., Conclusions: Weissella paramesenteroides WpK4 was able to increase the protection of the intestinal mucosa against experimental amoebic colitis through the increase of MUC-2 and epithelial regeneration., Significance and Impact of the Study: Weissella paramesenteroides WpK4 presents the potential to become a complementary tool in the treatment of amoebic colitis., (© 2020 The Society for Applied Microbiology.)

The microbiome provides resistance to infection. However, the underlying mechanisms are poorly understood. We demonstrate that colonization with the intestinal bacterium Clostridium scindens protects from Entamoeba histolytica colitis via innate immunity. Introduction of C. scindens into the gut microbiota epigenetically altered and expanded bone marrow granulocyte-monocyte progenitors (GMPs) and resulted in increased intestinal neutrophils with subsequent challenge with E. histolytica. Introduction of C. scindens alone was sufficient to expand GMPs in gnotobiotic mice. Adoptive transfer of bone marrow from C. scindens-colonized mice into naive mice protected against amebic colitis and increased intestinal neutrophils. Children without E. histolytica diarrhea also had a higher abundance of Lachnoclostridia. Lachnoclostridia C. scindens can metabolize the bile salt cholate, so we measured deoxycholate and discovered that it was increased in the sera of C. scindens-colonized specific pathogen-free and gnotobiotic mice, as well as in children protected from amebiasis. Administration of deoxycholate alone increased GMPs and provided protection from amebiasis. We elucidated a mechanism by which C. scindens and the microbially metabolized bile salt deoxycholic acid alter hematopoietic precursors and provide innate protection from later infection with E. histolytica.

Entamoeba histolytica is the causative agent of amebiasis, an infectious disease targeting the intestine and the liver in humans. Two types of intestinal infection are caused by this parasite: silent infection, which occurs in the majority of cases, and invasive disease, which affects 10% of infected persons. To understand the intestinal pathogenic process, several in vitro models, such as cell cultures, human tissue explants or human intestine xenografts in mice, have been employed. Nevertheless, our knowledge on the early steps of amebic intestinal infection and the molecules involved during human-parasite interaction is scarce, in part due to limitations in the experimental settings. In the present work, we took advantage of tissue engineering approaches to build a three-dimensional (3D)-intestinal model that is able to replicate the general characteristics of the human colon. This system consists of an epithelial layer that develops tight and adherens junctions, a mucus layer and a lamina propria-like compartment made up of collagen containing macrophages and fibroblast. By means of microscopy imaging, omics assays and the evaluation of immune responses, we show a very dynamic interaction between E. histolytica and the 3D-intestinal model. Our data highlight the importance of several virulence markers occurring in patients or in experimental models, but they also demonstrate the involvement of under described molecules and regulatory factors in the amoebic invasive process., (© 2020 John Wiley & Sons Ltd.)

Competing Interests: All authors declare that there are no competing interests regarding the present report.

Amoebic colitis represents a common parasitic infection in developing countries. In western world, it is encountered only sporadically. The clinical presentation is usually non-specific, non-invasive laboratory tests are often false negative and endoscopic and histopathological appearance may mimic other illnesses, especially Crohns disease. The disease therefore harbours a huge risk of misdiagnosing and a proper diagnosis is usually challenging. We present a case of an amoebic colitis with Crohn-like features and negative parasitological testing in a 53-years-old woman, in which the final diagnosis was established on the basis of its histopathological examination.

Entamoeba histolytica ( Eh ) is a protozoan parasite of humans that colonizes the outer colonic mucus layer. Under conditions not fully understood, Eh breaches innate host defenses and invades the intestinal mucosa-causing amebic colitis and liver abscess. In asymptomatic infection, Eh interacts with and feeds on resident microbiota that forms biofilms on the outer colonic mucus layer. Despite the close association between Eh and commensal microbiota, we still lack basic knowledge on whether microbiota and/or their metabolites influence Eh virulence traits critical in disease pathogenesis. In the pathogenesis of intestinal amebiasis, Eh overcomes the protective mucus layer using a combination of mucinase/glycosidase and potent mucus secretagogue activity. In this addendum, we discuss the interconnected role of a healthy mucus barrier and the role commensal microbiota play in shaping innate host defense against Eh -induced pro-inflammatory and secretory responses critical in disease pathogenesis.

Entamoeba histolytica is a protozoan parasite that affects a large proportion of the world's population and causes amoebic dysentery and extra-intestinal disease. Many individuals remain asymptomatic during colonisation; in 10% of individuals, the parasite breaks through the mucosal barrier and leads to invasive disease. An eight-month-old girl who was evaluated for hypo-albuminaemia and was diagnosed with amoebic colitis is reported. To the best of our knowledge, this is the first report of hypo-albuminaemia owing to amoebic colitis in any age group.

A case of amoebic colitis and liver abscess is described in a previously fit 59-year old man who had been given the incorrect diagnosis of ulcerative colitis. His symptoms were so severe that a colectomy was being considered. The patient had a significant travel history including trips to Morocco, the Gambia and Cape Verde, putting him at risk of acquiring amoebic disease. However, this history was not ascertained until much later on in the disease process. The case highlighted crucial learning points including the importance of taking a lifelong travel history, the difficulties in telling ulcerative colitis and amoebic colitis apart both clinically and histopathologically, and the importance of sending multiple stool samples for parasitological microscopy analysis in patients being investigated for inflammatory bowel disease.

Understanding the mechanisms by which Entamoeba histolytica drives gut inflammation is critical for the development of improved preventive and therapeutic strategies. E. histolytica encodes a homolog of the human cytokine macrophage migration inhibitory factor (MIF). Here, we investigated the role of E. histolytica MIF (EhMIF) during infection. We found that the concentration of fecal EhMIF correlated with the level of intestinal inflammation in persons with intestinal amebiasis. Mice treated with antibodies that specifically block EhMIF had reduced chemokine expression and neutrophil infiltration in the mucosa. In addition to antibody-mediated neutralization, we used a genetic approach to test the effect of EhMIF on mucosal inflammation. Mice infected with parasites overexpressing EhMIF had increased chemokine expression, neutrophil influx, and mucosal damage. Together, these results uncover a specific parasite protein that increases mucosal inflammation, expands our knowledge of host-parasite interaction during amebic colitis, and highlights a potential immunomodulatory target., (© The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

Amebiasis is uncommon in developed countries. Several case reports in the literature emphasize that both the presenting symptoms and the radiological findings of colonic amebiasis closely resemble more common conditions, such as idiopathic inflammatory bowel disease and gastro-intestinal malignancy. We describe a unique case of colonic amebiasis (amebomas) coexisting with signet-ring cell carcinoma of the ileocecal valve, the cecum and the appendix. Endoscopically, the ulcerated tumor was indistinguishable from the ulcerations and pseudotumors (amebomas) detected in the ascending colon. Histological examination of biopsy specimens revealed the pathognomonic features of protozoa with ingested erythrocytes in combination with signet-ring cell infiltration. The author concludes that amebiasis may not only mimic carcinoma but, rarely, may coexist with carcinoma in the same patient. Clinicians and pathologists should be aware of this possibility in order not to delay diagnosis and treatment of malignant disease., Competing Interests: Conflict-of-interest statement: The author has no conflicts of interests to declare.

Background: Amebic colitis, caused by intestinal infection with the parasite, Entamoeba histolytica, is a common cause of diarrhea worldwide. Fulminant amebic colitis is the most devastating complication of this infection, associated with both high mortality and morbidity. We conducted a review of the English literature to describe cases of fulminant amebic colitis associated with exposure to corticosteroid medications in order to identify the risk factors for poor outcome and determine difficulties in diagnosis and treatment., Methodology and Principal Findings: Articles reporting severe and fulminant forms of amebic colitis between 1991 and 2016 were collected. 525 records were screened to identify 24 cases for qualitative analysis associated with corticosteroid use. Cases arose from areas of high endemicity or travel to such areas. Most cases (14 of 24, 58%) were given corticosteroids for initially misdiagnosed colitis, mainly inflammatory bowel, resulting in rapid progression of disease. Nearly half of all cases underwent surgical intervention, and 25% of cases died, despite all patients eventually receiving treatment with metronidazole. The odds of death did not differ significantly by prior misdiagnosis, co-morbidities, bowel perforation or need for surgery., Conclusions and Significance: Infection with E. histolytica should be considered prior to the administration of corticosteroids, in particular for patients residing in endemic areas or those with appropriate travel history, especially prior to the diagnosis of inflammatory bowel disease. The development of preventative and treatment interventions are needed to improve outcomes of fulminant disease.

Critical to the pathogenesis of intestinal amebiasis, Entamoeba histolytica (Eh) induces mucus hypersecretion and degrades the colonic mucus layer at the site of invasion. The parasite component(s) responsible for hypersecretion are poorly defined, as are regulators of mucin secretion within the host. In this study, we have identified the key virulence factor in live Eh that elicits the fast release of mucin by goblets cells as cysteine protease 5 (EhCP5) whereas, modest mucus secretion occurred with secreted soluble EhCP5 and recombinant CP5. Coupling of EhCP5-αvβ3 integrin on goblet cells facilitated outside-in signaling by activating SRC family kinases (SFK) and focal adhesion kinase that resulted in the activation/phosphorlyation of PI3K at the site of Eh contact and production of PIP3. PKCδ was activated at the EhCP5-αvβ3 integrin contact site that specifically regulated mucin secretion though the trafficking vesicle marker myristoylated alanine-rich C-kinase substrate (MARCKS). This study has identified that EhCP5 coupling with goblet cell αvβ3 receptors can initiate a signal cascade involving PI3K, PKCδ and MARCKS to drive mucin secretion from goblet cells critical in disease pathogenesis.

Background: Intestinal amebiasis is one of the important differential diagnoses of Inflammatory Bowel Disorders in areas where it is highly prevalent., Aim: Studies comparing the clinical, endoscopic and histological features of these disorders have never been done, so we undertook this study., Materials and Methods: A retrospective study comparing mucosal biopsies of 14 consecutive cases of intestinal amebiasis with 14 cases of Ulcerative colitis and 12 cases of Crohn's disease. A total of 65 biopsies from patients with amebiasis, 56 biopsies from patients with Crohn's disease and 65 biopsies of patients with Ulcerative colitis were reviewed., Results and Conclusions: Discrete small ulcers less than 2 cm in diameter in the cecum or rectosigmoid, with intervening normal mucosa, were the most common finding on endoscopy in patients with amebiasis. On histology, necrotic material admixed with mucin, proteinaceous exudate and blood clot lining ulcers, significant surface epithelial changes such as shortening and tufting adjacent to sites of ulceration, mild chronic inflammation extending into the deep mucosa and mild architectural alteration were features of amebiasis. Trophozoite forms of ameba were seen in the necrotic material lining sites of ulceration or lying separately, as well as over intact mucosa. Necrotic material lining ulcers was less common in IBD, but chronic inflammation, crypt abscess formation and architectural alteration were more severe.

We present a case of a 30-year-old postpartum woman who delivered by caesarean section at 34 weeks. On postoperative day 9, she was admitted to our hospital in shock. Emergency abdominal surgery was performed. Massive purulent ascites collected in the abdominal cavity and was associated with intestinal necrosis, which extended from the ascending colon to one-third of the descending colon. The necrotic lesion was excised, and an artificial anus was constructed at the ileum end. A histological finding on the 15th day indicated the possibility of amoebic enteritis, and the patient was started on metronidazole therapy. The diarrhoea improved dramatically after metronidazole treatment was started. The patient was able to walk unassisted on the 45th day and was subsequently discharged. Amoebic enteritis has been thought to be epidemic in developing countries, but today, the incidence of amoebic enteritis as a sexually transmitted disease is increasing in developed countries., (2015 BMJ Publishing Group Ltd.)

A retrospective cohort study was conducted in 55 symptomatic patients with amebic colitis that visited at St. Luke's International Hospital and Mie University Hospital from 1994 through 2013. To diagnose amebic colitis, 40 patients underwent total colonoscopy within 1 week after hospital visiting and before receiving any treatment. The percentage of characteristic endoscopic findings of amebic colitis including discrete ulcers or erosions with white or yellow exudates were 0% in terminal ileum, 93% in cecum, 28% in ascending, 25% in transverse, 15% in descending, 20% in sigmoid colon and 45% in rectum. The rectal lesions in 55% of patients with amebic colitis were nonspecific. The trophozoite identification rate by direct smear of intestinal tract washings performed during colonoscopy was 88%. The protozoan identification rate was 70% in biopsy specimens taken from the periphery of the characteristic discrete ulcers. Total colonoscopy should be considered for the diagnosis of amebic colitis., (Copyright © 2015 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

The administration of metronidazole is generally effective to treat amebic colitis. Fulminant amebic colitis is relatively rare, and it is associated with a high mortality rate. Three cases of fulminant amebic colitis were diagnosed in our hospital between 1993 and 2014. One of these patients died despite our efforts. Amebic colitis often presents with no obvious risk factors and with atypical clinical symptoms. Therefore, the diagnosis of amebic colitis can be difficult. Early diagnosis is the most important factor in successful treatment of fulminant amebic colitis. The present cases demonstrate that it is important to consider the possibility of amebic colitis during evaluation of the acute abdomen.

Aims: To review the clinical and pathological factors associated with fulminant amoebic colitis (FAC) requiring colonic resection and its outcome., Methods: We retrospectively identified adult patients admitted to our centre between June 2007 and December 2011 with FAC who underwent colonic resection and were diagnosed with amoebic colitis based on the presence of trophozoites on histological examination. The clinical details were extracted from the medical notes and correlated with the pathological findings., Results: Thirty patients (18 men and 12 women) met the inclusion criteria. Their mean age was 50.1 years (range 21-89). The most frequent symptoms were abdominal pain, vomiting and fever. More than half the patients (16/30) had underlying conditions associated with immunosuppression including diabetes mellitus and tuberculosis. Pathological investigation of colonic resections showed predominantly right-sided involvement with geographic colonic ulcers covered with a creamy-white pseudomembrane, perforations, gangrenous changes, amoeboma and lesions mimicking inflammatory bowel disease. All showed basophilic dirty necrosis with abundant nuclear debris and amoebic trophozoites on histological examination. 21/30 patients (70%) had involvement beyond the caecum. 17/30 patients (57%) died. Those with involvement beyond the caecum were more likely to die (15/21, 71.4%) than those with less extensive disease., Conclusions: FAC presents as acute abdomen and can mimic appendicitis, ischaemic bowel disease, tuberculosis and malignancy. Comorbidities causing immunosuppression frequently associated. Mortality remains high despite surgery, so FAC should be suspected in every case of acute abdomen with colonic perforation if associated with typical gross and microscopic findings and a history of stay in an endemic area., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

The Entamoeba histolytica-methylated LINE-binding protein (EhMLBP) binds to methylated repetitive DNA and is a positive regulator of a reverse transcriptase of a long interspersed nucleotide element (LINE). This protein protects trophozoites against heat shock by reducing protein aggregation. The presence of EhMLBP and polyubiquitinated proteins in heat shock-induced protein aggregates raised the question whether these proteins interact. This assumption was confirmed by co-immunoprecipitation experiments: ubiquitinated proteins were detected in the perinuclear region of non-stressed E. histolytica trophozoites, whereas ubiquitinated proteins were detected in the perinuclear region and colocalized with EhMLBP in cytoplasmic granules in heat-shocked trophozoites. We also observed that overexpression of the reverse transcriptase of EhRLE3 induced the upregulation of EhMLBP expression and the formation of these EhMLBP-containing granules. Since (i) these EhMLBP-containing granules in the cytoplasm of heat-shocked E. histolytica trophozoites also contain polyubiquitinated proteins and poly(A)(+) mRNA and (ii) their formation is promoted by sodium arsenate, puromycin, and pateamine A and is inhibited by cycloheximide, we propose that these cytoplasmic EhMLBP-containing granules are stress granules. Our data also suggest that the formation of these granules is dependent upon EhMLBP and LINE., (© 2014 John Wiley & Sons Ltd.)

We present a case of amoebic colitis, misdiagnosed as inflammatory bowel disease and treated with corticosteroids, leading to severe necrotizing enterocolitis. We review the literature on the epidemiology, pathogenesis, diagnosis, and treatment of amoebic dysentery, with special emphasis on the association between immunosuppressive treatment and the development of severe invasive amoebiasis.

The emergence of amoebiasis is of great public health concern since it has the potential to become endemic in developed nations essentially due to increased travel to endemic areas, emigration of people from affected nations and increase in the HIV-AIDS population. Fulminant necrotizing amoebic colitis is a rare and relatively less-known form of amoebiasis typically associated with very high morbidity and mortality, as is presented in the current case., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Background: Toxic or fulminant colitis due to Entamoeba histolytica infrequently presents but is very serious. Unfortunately, there are numerous contradictory factors related to mortality., Methods: We analyzed several cases of E. histolytica infection to determine the factors related to mortality. We included patients >15 years of age who were histopathologically diagnosed with amoebic toxic colitis and treated from January 2000 through December 2006. We evaluated demographic, clinical, laboratorial, surgical, and histopathological characteristics., Results: We examined 24 patients and recorded 12 deaths (50%). Twenty patients underwent surgery within a mean time of 24 hours (range: 8-120 hours). Tenesmus and intestinal perforation were determined to be statistically significant (P<0·05) by univariate analysis. Three models of logistic regression were able to determine three statistically significant factors that affected mortality: (1) tenesmus and a lymphocyte count <1·5×10(3) cell/μl; 2) depth of invasion beyond the mucosa and a lymphocyte count <1·5×10(3) cell/μl; 3) time spent with symptoms and perforation., Conclusions: The mortality rate determined in this study is similar to previously reported series. A low lymphocyte count, significant depth of invasion, and intestinal perforation were determined to be the factors related to increased mortality, while tenesmus and limited amount of time spent with symptoms were associated with survival. Quick diagnosis and appropriate treatment are important factors that reduce mortality.

A 75-year-old man was admitted because of watery diarrhea, hematochezia and right lower abdominal pain. Many deep undermining colonic ulcers were found by colonoscopy, and we detected trophozoite amoeba pathologically. Metronidazole was administered orally from 3 days after admission. However, since CT demonstrated a huge abscess in the abdominal cavity, we performed percutaneous drainage from 17 days after admission. On day 157, the patient was discharged, because the colonic ulcers had almost healed, and trophozoite amoebas were not recognized pathologically.

The enteric protozoan parasite Entamoeba histolytica is the cause of potentially fatal amebic colitis and liver abscesses. E. histolytica trophozoites colonize the colon, where they induce inflammation, penetrate the mucosa, and disrupt the host immune system. The early establishment of E. histolytica in the colon occurs in the presence of antimicrobial human (LL-37) and murine (CRAMP [cathelin-related antimicrobial peptide]) cathelicidins, essential components of the mammalian innate defense system in the intestine. Studying this early step in the pathogenesis of amebic colitis, we demonstrate that E. histolytica trophozoites or their released proteinases, including cysteine proteinase 1 (EhCP1), induce intestinal cathelicidins in human intestinal epithelial cell lines and in a mouse model of amebic colitis. Despite induction, E. histolytica trophozoites were found to be resistant to killing by these antimicrobial peptides, and LL-37 and CRAMP were rapidly cleaved by released amebic cysteine proteases. The cathelicidin fragments however, did maintain their antimicrobial activity against bacteria. Degradation of intestinal cathelicidins is a novel function of E. histolytica cysteine proteinases in the evasion of the innate immune system in the bowel. Thus, early intestinal epithelial colonization of invasive trophozoites involves a complex interplay in which the ultimate outcome of infection depends in part on the balance between degradation of cathelicidins by amebic released cysteine proteinases and upregulation of proinflammatory mediators which trigger the inflammatory response.

Objective: To determine the level of oxygen-nitrogen stress parameters in the pathogenesis of amebiasis., Methods: Twenty-four acute intestinal amebiasis patients and 20 healthy controls were enrolled in the present study. Serum malondialdehyde and nitric oxide levels were determined spectrophotometrically., Results: Serum malondialdehyde and nitric oxide levels were significantly higher in acute intestinal amebiasis patients than healthy controls (P<0.001)., Conclusions: These results suggest that oxidative and nitrosative stress may play a major role in tissue damage in acute intestinal amebiasis patients. Also these parameters can be used to supplement the conventional microscopic method for reliable diagnosis of intestinal amebiasis.

Entamoeba histolytica is the causative agent of amebiasis, a disease that is a major source of morbidity and mortality in the developing world. The potent cytotoxic activity of the parasite appears to underlie disease pathogenesis, although the mechanism is unknown. Recently, progress has been made in determining that the parasite activates apoptosis in target cells and some putative effectors have been identified. Recent studies have also begun to unravel the host genetic determinants that influence infection outcome. Thus, we are beginning to get a clearer picture of how this parasite manages to infect, invade and ultimately inflict devastating tissue destruction.

Diarrhoea is a common presenting complaint to the Acute Medical Unit. We report a case of acute fulminant necrotizing amebic colitis in a 73 year old man with no recent travel history preceding his admission. Such cases are often difficult to diagnose and hence associated with a high mortality, unless treated promptly and appropriately. This case report highlights the importance of early diagnosis and prompt initiation of treatment.

The enteric protozoan parasite Entamoeba histolytica causes amebic colitis through disruption of the mucus layer, followed by binding to and destruction of epithelial cells. However, it is not known whether ameba infections or ameba components can directly affect the enteric nervous system. Analysis of mucosal innervations in the mouse model of cecal amebiasis showed that axon density was diminished to less than 25% of control. To determine whether amebas directly contributed to axon loss, we tested the effect of either E. histolytica secreted products (Eh-SEC) or soluble components (Eh-SOL) to an established coculture model of myenteric neurons, glia, and smooth muscle cells. Neuronal survival and axonal degeneration were measured after 48 h of exposure to graded doses of Eh-SEC or Eh-SOL (10 to 80 μg/ml). The addition of 80 μg of either component/ml decreased the neuron number by 30%, whereas the axon number was decreased by 50%. Cytotoxicity was specific to the neuronal population, since the glial and smooth muscle cell number remained similar to that of the control, and was completely abrogated by prior heat denaturation. Neuronal damage was partially prevented by the cysteine protease inhibitor E-64, showing that a heat-labile protease was involved. E. histolytica lysates derived from amebas deficient in the major secreted protease EhCP5 caused a neurotoxicity similar to that of wild-type amebas. We conclude that E. histolytica infection and ameba protease activity can cause selective damage to enteric neurons.

Acute appendicitis of amebic origin is considered a rare cause of acute appendicitis. We report a case of amebic appendicitis presenting with fever, severe pain in the right lower quadrant of the abdomen and rebound tenderness. Lab investigations revealed neutrophilic leukocytosis. The patient underwent appendectomy. Histopathological examination revealed numerous Entameba histolytica trophozoites in the mucosa of the appendix. Acute appendicitis of amebic origin does not appear frequently. Appendicular amebiasis can give the clinical features of acute appendicitis and should be treated accordingly.

Background: The endocytoscopy system (ECS) is a new method to provide real-time super-magnifying microscopic imaging in vivo. Routine diagnosis of amebic colitis requires multiple tests that are both time consuming and costly., Objective: To determine the feasibility of ECS to directly detect the amebic parasites in vivo., Design: Prospective, single-center, pilot study., Setting: Tertiary-care university hospital., Patients: This study involved 5 patients who were suspected to have amebic colitis by conventional colonoscopy in our institute., Interventions: A super-magnifying ECS with 450 x magnification., Main Outcome Measurements: We compared ECS findings with those of conventional methods-serum antibody tests and histology of colon biopsy specimens., Results: We successfully visualized the amebic trophozoites in all 5 cases. In contrast, 3 specimens had positive results on serology, and 3 had positive histology results on hematoxylin and eosin staining., Limitations: Pilot study with a limited number of patients. Findings were compared only with serology and histology findings., Conclusions: ECS would be a useful tool for the prompt diagnosis of amebic colitis via the real-time in vivo visualization of amebic trophozoites., (Copyright 2010 American Society for Gastrointestinal Endoscopy. Published by Mosby, Inc. All rights reserved.)

Entamoeba histolytica is the protozoan parasite that causes amebic colitis. The parasite triggers apoptosis on contact with host cells; however, the biological significance of this event during intestinal infection is unclear. We examined the role of apoptosis in a mouse model of intestinal amebiasis. Histopathology revealed that abundant epithelial cell apoptosis occurred in the vicinity of amoeba in histological specimens. Epithelial cell apoptosis occurred rapidly on co-culture with amoeba in vitro as measured by annexin positivity, DNA degradation, and mitochondrial dysfunction. Administration of the pan caspase inhibitor ZVAD decreased the rate and severity of amebic infection in CBA mice by all measures (cecal culture positivity, parasite enzyme-linked immunosorbent assay, and histological scores). Similarly, caspase 3 knockout mice on the resistant C57BL/6 background exhibited even lower cecal parasite antigen burden and culture positive rates than wild type mice. The permissive effect of apoptosis on infection could be tracked to the epithelium, in that transgenic mice that overexpressed Bcl-2 in epithelial cells were more resistant to infection as measured by cecal parasite enzyme-linked immunosorbent assay and histological scores. We concluded that epithelial cell apoptosis in the intestine facilitates amebic infection in this mouse model. The parasite's strategy for inducing apoptosis may point to key virulence factors, and therapeutic maneuvers to diminish epithelial apoptosis may be useful in amebic colitis.

Background: Amebiasis is a worldwide health problem that mainly affects developing countries. Invasive amebiasis tends to develop complications, and among these, perforation of the colon, although infrequent (1.9-9.1%), is the most lethal. Surgical treatment in these cases should be carried out in a timely fashion prior to the presentation of systemic repercussions or death. In the present study, we analyzed a total of 122 cases of invasive amebiasis-associated colon perforation., Methods and Study Design: We conducted a clinical, retrospective, and observational study and presented cases of colonic perforation observed over the past 30 years at the Medical-Surgical Emergency Service of the Mexico City-based Hospital General de México OD during the 1970-1999 period., Results: During this time, a total of 19,916 emergency abdominal surgeries were performed. One hundred twenty-two of these procedures corresponded to cases of colon perforation by ameba, which represents 0.6%; 80 patients were men (65.6%) and 42 were women (34.4%), with an average age of 48 years. Multiple colon perforation was 74%, with right colon the most affected (90.5%). Depending on the perforation's extension and localization, right hemicolectomy with ileostomy were performed in 53 patients (43.45%), subtotal colectomy with ileostomy in 43 (35.25%), left hemicolectomy with transverse colostomy in 12 (9.83%), exteriorization of perforated left colon (stoma) in 13 (10.65%), and primary closure with exteriorization in one patient (0.8%). Post-operative complications were present in 48 patients (39.3%), and 20 cases were related with the creation of a stoma. Eighteen of these cases were due to persistent abdominal sepsis and ten due to toxic colon; the latter correspond solely to patients with initial nonresective treatment. General mortality was 40%, with 32% (17 of 53 cases) of mortality in those submitted to right hemicolestomy, 16.7% (two of 12) of left hemicolestomy, 44.2% (19 of 43) in those in whom a subtotal colectomy was performed, with 76.9% (ten of 13) patients with exteriorization of the perforated right colon, and with 100% (one of one patient) mortality with primary closure., Conclusions: Perforation is the most frequent surgical complication of invasive amebiasis of the colon, occurring principally in masculine gender and in the fourth decade of life. Resection and stoma creation is the procedure of choice that can resolve the septic focus from the first surgical procedure, depending on the general status of the patient. However, morbidity and mortality are high, and there is a tendency for these to be lower on comparing initial cases with those with recently conducted surgical procedures.

A 52-year-old man had bloody stools during chemotherapy for gastric cancer. A colonoscopy revealed necrotizing ulcer-like changes. A biopsy confirmed the presence of amoebic trophozoites. Subsequently, peritonitis with intestinal perforation developed, and emergency peritoneal lavage and colostomy were performed. After surgery, endotoxin adsorption therapy was performed and metronidazole was given. Symptoms of peritonitis and colonitis resolved. However, the patient's general condition worsened with the progression of gastric cancer. The patient died 50 d after surgery. Fulminant amoebic colitis is very rarely associated with chemotherapy. Amoebic colitis should be considered in the differential diagnosis of patients who have bloody stools during chemotherapy.

Background: Amebic colitis although common, rarely presents as fulminant colitis which has a high morbidity and mortality unless treated promptly and appropriately., Aim: To study the clinical, morphological features and outcome of fulminant amebic colitis (FAC)., Materials and Methods: A retrospective study of six patients who underwent surgical resections from 2002-06 and were diagnosed with FAC, was carried out. The morphological features assessed included the average number of trophozoites per high-power field and the depth of invasion of trophozoites into the muscularis propria., Results: The study included five adults and one child who underwent surgery for fulminant colitis. Interestingly, a definite preoperative diagnosis of amebic colitis was made only in one patient and suspected in another. Intraoperatively, multiple perforations of the intestine with peritonitis were the most common findings. Gross examination typically revealed multiple ulcers with exudate and intervening normal mucosa. Microscopically, ulceration and myonecrosis with trophozoites within the exudate were seen in all cases. Trophozoites invading the muscularis propria were seen in five cases. Of the cases that showed myoinvasion by trophozoites, two patients expired within two weeks of surgery. One of the patients who expired also showed co-infection with Actinomyces., Conclusion: FAC is an uncommon outcome in amebic colitis with a high mortality requiring prompt surgical intervention.

Background: It has been suggested that the damage observed in invasive amebiasis is related to interactions between polymorphonuclear leukocytes (PMN) and Entamoeba histolytica trophozoites. We analyzed the relation between infiltrating inflammatory cell populations and E. histolytica density in intestinal amebic lesions., Methods: Biopsies obtained endoscopically from patients with amebic colitis were analyzed to describe their morphologic abnormalities. Cellular populations and E. histolytica trophozoites were measured quantitatively in order to assess the correlation between infiltrating inflammatory cell populations and parasite density., Results: Amebic lesions were most often located in the colon (55%). The histopathologic diagnoses were colitis in 31%, erosive colitis in 26%, and ulcerated colitis in 24%. The predominant cellular populations found in the lesions were lymphocytes (59.8%) (3,672 +/- 2,413/mm(2)) followed by PMN (17%) (1,038 +/- 1,171 PMN/mm(2)) (p < 0.01). A higher density of PMN infiltration was observed in severe cases. Cellular populations predictive of the presence of E. histolytica trophozoites (p = 0.047) were PMN (p = 0.019) and lymphocytes (p = 0.033). The highest association was found between E. histolytica trophozoites and PMN (p = 0.0221)., Conclusions: Neutrophils and lymphocytes, particularly the former, are associated significantly with the density of parasites. Our findings support the theory that PMN interaction with E. histolytica contributes to the pathogenesis of amebic intestinal lesions.

Biopsies of 11 patients with histopathologically diagnosed amebic colitis was evaluated; endoscopically, they were suspected to have tuberculosis or inflammatory bowel disease. Amebiasis was suggested in the differential diagnosis in only 3 cases. Three patients had purely rectal or sigmoid involvement, whereas the others had ileocecal, cecal, ascending, or transverse colon disease. The biopsies showed cryptitis and depletion of mucin but no crypt branching. Crypt abscesses were seen in one biopsy. Trophozoites of Entamoeba histolytica were seen in the exudate in all cases. The trophozoites were round to oval, approximately 25 to 40 microm in diameter and had a single, round nucleus and periodic acid-Schiff-positive cytoplasm. Phagocytosed erythrocytes were present in the trophozoites. Some features of ulcerative colitis and infectious colitis, such as cryptitis and crypt abscesses, are also seen in amebic colitis. Amebic colitis must be included in the differential diagnosis of all patients with suspected inflammatory bowel disease and tuberculosis.

The protozoan intestinal parasite Entamoeba histolytica infects millions of people worldwide and is capable of causing amebic dysentery and amebic liver abscess. The closely related species Entamoeba dispar colonizes many more individuals, but this organism does not induce disease. To identify molecular differences between these two organisms that may account for their differential ability to cause disease in humans, we used two-dimensional gel-based (DIGE) proteomic analysis to compare whole cell lysates of E. histolytica and E. dispar. We observed 141 spots expressed at a substantially (>5-fold) higher level in E. histolytica HM-1:IMSS than E. dispar and 189 spots showing the opposite pattern. Strikingly, 3 of 4 proteins consistently identified as different at a greater than 5-fold level between E. histolytica HM-1:IMSS and E. dispar were identical to proteins recently identified as differentially expressed between E. histolytica HM-1:IMSS and the reduced virulence strain E. histolytica Rahman. One of these was E. histolytica alcohol dehydrogenase 3 (EhADH3). We found that E. histolytica possesses a higher level of NADP-dependent alcohol dehydrogenase activity than E. dispar and that some EhADH3 can be localized to the surface of E. histolytica. Episomal overexpression of EhADH3 in E. histolytica trophozoites resulted in only subtle phenotypic differences in E. histolytica virulence in animal models of amebic colitis and amebic liver abscess, making it difficult to directly link EhADH3 levels to virulence differences between E. histolytica and less-pathogenic Entamoeba.