Entamoeba histolytica exploits the autophagy pathway in macrophages to trigger inflammation in disease pathogenesis.

The mechanism whereby Entamoeba histolytica (Eh) binding with macrophages at the intercellular junction triggers aggressive pro-inflammatory responses in disease pathogenesis is not well understood. The host intracellular protein degradation process autophagy and its regulatory proteins are involved in maintenance of cellular homeostasis and excessive inflammatory responses. In this study we unraveled how Eh hijacks the autophagy process in macrophages to dysregulate pro-inflammatory responses. Direct contact of live Eh with macrophages activated caspase-6 that induced rapid proteolytic degradation of the autophagy ATG16L1 protein complex independent of NLRP3 inflammasome and caspase-3/8 activation. Crohn's disease susceptible ATG16L1 T300A variant was highly susceptible to Eh-mediated degradation that augmented pro-inflammatory cytokines in mice. Quantitative proteomics revealed downregulation of autophagy and vesicle-mediated transport and upregulation of cysteine-type endopeptidase pathways in response to Eh. We conclude during Eh-macrophage outside-in signaling, ATG16L1 protein complex plays an overlooked regulatory role in shaping the pro-inflammatory landscape in amebiasis.

Intestinal parasites including Cryptosporidium, Cyclospora, Giardia, and Microsporidia, Entamoeba histolytica, Strongyloides, Schistosomiasis, and Echinococcus: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice.

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of intestinal parasites in the pre- and post-transplant period. Intestinal parasites are prevalent in the developing regions of the world. With increasing travel to and from endemic regions, changing immigration patterns, and the expansion of transplant medicine in developing countries, they are increasingly recognized as a source of morbidity and mortality in solid-organ transplant recipients. Parasitic infections may be acquired from the donor allograft, from reactivation, or from de novo acquisition post-transplantation. Gastrointestinal multiplex assays have been developed; some of the panels include testing for Cryptosporidium, Cyclospora, Entamoeba histolytica, and Giardia, and the performance is comparable to conventional methods. A polymerase chain reaction test, not yet widely available, has also been developed to detect Strongyloides in stool samples. New recommendations have been developed to minimize the risk of Strongyloides donor-derived events. Deceased donors with epidemiological risk factors should be screened for Strongyloides and recipients treated if positive as soon as the results are available. New therapeutic agents and studies addressing the optimal treatment regimen for solid-organ transplant recipients are unmet needs.

First molecular epidemiology of Entamoeba histolytica, E. dispar and E. moshkovskii infections in Yemen: different species-specific associated risk factors.

OBJECTIVES: To investigate the molecular epidemiology of Entamoeba histolytica, E. dispar and E. moshkovskii infections among rural communities in Yemen. METHODS: In a community-based study, faecal samples were collected from 605 participants and examined by wet mount, formalin-ether sedimentation, trichrome staining and nested multiplex PCR techniques. Demographic, socio-economic and environmental information was collected using a pre-tested questionnaire. RESULTS: Overall, 324 (53.6%) of the samples were positive for Entamoeba cysts and/or trophozoites by microscopic examination. Molecular analysis revealed that 20.2%, 15.7% and 18.2% of the samples were positive for E. histolytica, E. dispar and E. moshkovskii, respectively. Multivariate analysis showed different sets of species-specific risk factors among these communities. Educational level was identified as the significant risk factor for E. histolytica; age and gender were the significant risk factors for E. moshkovskii; and sources of drinking water and consumption of unwashed vegetables were the significant risk factors for E. dispar. Moreover, living in coastal/foothill areas and presence of other infected family members were risk factors for both E. histolytica and E. moshkovskii infections. CONCLUSION: The study reveals that Entamoeba spp. infection is highly prevalent among rural communities in Yemen, with E. histolytica, E. dispar and E. moshkovskii differentiated for the first time. Identifying and treating infected family members, providing health education pertinent to good personal and food hygiene practices and providing clean drinking water should be considered in developing a strategy to control intestinal parasitic infections in these communities, particularly in the coastal/foothill areas of the country.

Febrile neutropenia in the tropics: a description of clinical and microbiological findings and their impact on inappropriate therapy currently used at an oncological reference center in Colombia.

INTRODUCTION: Febrile neutropenia is a common complication of chemotherapy treatment of malignant hematological diseases. However, there is insufficient information regarding the infectious complications of febrile neutropenia in our country. Objective. We will evaluate the microbial characteristics of bacterial and fungal isolates and the clinical outcome of patients with febrile neutropenia who received medical attention at an oncological reference center in Colombia. MATERIALS AND METHODS: A prospective case series included patients with histologically confirmed oncological disease, who were admitted because of febrile neutropenia or presented with febrile neutropenia during hospitalization. Patients with benign hematological diseases were excluded. Demographic, microbiological, and clinical features as well as treatment and outcome information from patients with febrile neutropenia were obtained. We performed univariate and multivariate analyses, with mortality defined as the outcome. RESULTS: One hundred and thirty episodes of febrile neutropenia were identified in 104 patients. The mean patient age was 19, and 53% of the patients were male. Approximately 86% of the episodes occurred in patients with hematological disorders. An infectious site was identified in 65% of patients; 41% and 24% of the febrile neutropenia pateints´ episodes exhibited a localized infectious focus and developed bloodstream infections, respectively. The majority of infections were found in blood, urine, gastrointestinal tract, and soft tissue. Distribution analysis of microbiological isolates revealed 46.4% Gram-negative bacilli, 38.4% Gram-positive cocci, 8% fungi, and 7.1% parasites; there was a 7.7% mortality rate. Appropriate empirical antimicrobial therapy was a protection-related factor in multivariate analyses (OR= 0.17; 0.034 - 0.9 95% CI; p= 0.037). CONCLUSIONS: The mortality rate was relatively low and comparable to the rate reported by developed countries. Inappropriate empirical antimicrobial therapy was the main factor associated with mortality.

Febrile neutropenia in the tropics: A description of clinical and microbiological findings and their impact on inappropriate therapy currently used at an oncological reference center in Colombia / Neutropenia febril en el trópico: una descripción de los hallazgos clínicos y microbiológicos y el impacto de la terapia inapropiada que utilizan en un centro de referencia oncológica en Colombia

Introduction. Febrile neutropenia is a common complication of chemotherapy treatment of malignant hematological diseases. However, there is insufficient information regarding the infectious complications of febrile neutropenia in our country. Objective. We will evaluate the microbial characteristics of bacterial and fungal isolates and the clinical outcome of patients with febrile neutropenia who received medical attention at an oncological reference center in Colombia. Materials and methods. A prospective case series included patients with histologically confirmed oncological disease, who were admitted because of febrile neutropenia or presented with febrile neutropenia during hospitalization. Patients with benign hematological diseases were excluded. Demographic, microbiological, and clinical features as well as treatment and outcome information from patients with febrile neutropenia were obtained. We performed univariate and multivariate analyses, with mortality defined as the outcome. Results. One hundred and thirty episodes of febrile neutropenia were identified in 104 patients. The mean patient age was 19, and 53% of the patients were male. Approximately 86% of the episodes occurred in patients with hematological disorders. An infectious site was identified in 65% of patients; 41% and 24% of the febrile neutropenia pateints´ episodes exhibited a localized infectious focus and developed bloodstream infections, respectively. The majority of infections were found in blood, urine, gastrointestinal tract, and soft tissue. Distribution analysis of microbiological isolates revealed 46.4% Gram-negative bacilli, 38.4% Gram-positive cocci, 8% fungi, and 7.1% parasites; there was a 7.7% mortality rate. Appropriate empirical antimicrobial therapy was a protection-related factor in multivariate analyses (OR= 0.17; 0.034 - 0.9 95% CI; p= 0.037). Conclusions. The mortality rate was relatively low and comparable to the rate reported by developed countries. Inappropriate empirical antimicrobial therapy was the main factor associated with mortality.

Introducción. La neutropenia febril es una complicación frecuente de la quimioterapia para las neoplasias hematológicas. Se dispone de escasa información de sus complicaciones infecciosas en nuestro medio. Objetivo. Evaluar las características clínicas y microbiológicas de pacientes con neutropenia febril, así como su resultado clínico en una institución de referencia oncológica en Colombia. Materiales y métodos. Se conformó prospectivamente una serie de casos con pacientes con enfermedad oncológica confirmada, que consultaron o presentaron neutropenia febril durante la hospitalización. Se excluyeron aquellos con enfermedad hematológica benigna. Se recolectaron datos sobre variables demográficas, microbiológicas, clínicas, de tratamiento y de resultado de los pacientes. Se llevaron a cabo un análisis univariado y uno multivariado, con la mortalidad como resultado. Resultados. Se identificaron 130 episodios de neutropenia febril en 104 pacientes, con una edad media de 19 años y 53 % masculinos. El 86 % de los episodios ocurrieron en pacientes con alteraciones hematológicas. Se demostró infección en 65 % de los casos: 41 % con un foco infeccioso localizado y 27,7 % con bacteriemia. Los principales focos infecciosos se localizaron en el torrente sanguíneo, el aparato urinario, el sistema gastrointestinal, la piel y los tejidos blandos. De los aislamientos microbiológicos, 46,4 % fueron bacilos Gram negativos, 38,4 %, cocos Gram positivos, 9 %, hongos y, 7,1%, parásitos. La mortalidad global fue de 7,7 %. En el análisis multivariado la utilización de un tratamiento empírico apropiado se correlacionó con una menor mortalidad, de forma independiente (OR=0,17; IC 95% 0,034-0,9; p=0,037). Conclusiones. La tasa de mortalidad fue relativamente baja y fue comparable con lo reportado en países desarrollados. El tratamiento antimicrobiano inapropiado fue el principal factor asociado con mortalidad.

Entamoeba infected orbital cysts as a late complication to orbital floor fractures.

An unusual late complication to an orbital floor fracture is presented. Five years after trauma a now 22-year old man demonstrated an entamoeba infected cyst in the orbit.

[Invasive amebiasis at an institution for the mentally retarded in Shizuoka Prefecture].

Amebiasis caused by Entamoeba histolytica at an institution for mentally retarded in Shizuoka Prefecture is reported. Five of the 50 patients showed E. histolytica cysts in their stools and 4 were positive serologically. The polymerase chain reaction and restriction fragment length polymorphism revealed that the isolates were pathogenic-type E. histolytica. Epidemiological analysis revealed that the amebic infection was caused by the abnormal behavior of mentally retarded patients. Administration of diloxanide furoate and metronidazole for cyst-carriers eliminated cysts from the stool and lowered the antibody titer.

Interaction of laminin with Entamoeba histolytica cysteine proteinases and its effect on amebic pathogenesis.

The Entamoeba histolytica 27-kDa cysteine proteinases exhibit striking binding specificities for immobilized laminin over other components of the extracellular matrix, such as collagen and fibronectin. Inactivation of the proteinase with the active-site inhibitor L-trans-epoxysuccinyl-leucylamido(4-guanidino)butane abolishes laminin binding by the enzyme, and conversely, laminin inhibits cleavage of a fluorogenic dipeptide substrate of the amebic cysteine proteinase, suggesting that the substrate binding pocket of the enzyme is involved in the binding of laminin. The addition of laminin but not fibronectin or collagen to E. histolytica trophozoites significantly reduces amebic liver abscess formation in severe combined immunodeficient mice, further supporting the hypothesis that E. histolytica cysteine proteinases play an important role in amebic pathogenesis. The specific interaction of amebic proteinases with laminin may be exploited in designing new inhibitors of these enzymes.

Severe vaginal infection with Entamoeba histolytica in a woman who recently returned from Mexico: case report and review.

Genital amebiasis is a rare complication of infection with Entamoeba histolytica, even in areas where the pathogen is endemic. We describe a patient who apparently contracted intestinal amebiasis on a trip to Mexico and who presented with ulcerative vulvovaginitis 2 months later. Her condition rapidly progressed to severe necrotizing vulvovaginitis that required a radical vulvectomy. Histopathologic examination of the surgical specimen revealed the presence of E. histolytica trophozoites. The patient recovered after surgery and antiamebic therapy. We review the epidemiology and pathogenesis of genital amebiasis as well as therapy for this rare infection.

The pore-forming peptide of Entamoeba histolytica, the protozoan parasite causing human amoebiasis.

Amoebapore, the pore-forming peptide of E. histolytica has been isolated and its structure elucidated on the cDNA and protein level. The peptide is composed of 77 amino acid residues including six cysteine residues and has a molecular mass of 8244 Da. The primary translation product contains a signal sequence of 21 mostly hydrophobic amino acid residues. The active peptide has been located in the cytoplasmic granules of the amoebae. Circular dichroism spectroscopy revealed an all alpha-helical conformation and computer-aided secondary structure prediction yielded a structure of four helices. The helical conformation and three intramolecular disulfide bonds impart a highly compact and rigid structure upon the molecule. The activity of amoebapore, measured by a liposome depolarization assay, is resistant to heating at 100 degrees C in the absence of reducing agents. Synthetic peptides corresponding to the helices 1 and 3 exhibited pore-forming activity. Two minor, biologically active isoforms of amoebapore have amino acid sequence identity of 57% and 47%, respectively. Whereas amoebapore is a constituent of pathogenic E. histolytica isolates, nonpathogenic E. histolytica produce a structurally very similar peptide, the specific activity of which is approximately one third that of amoebapore. The biological significance of amoebapore for the pathogenicity of E. histolytica and specifically for its cytolytic activity remains to be determined.

Antigens in electron-dense granules from Entamoeba histolytica as possible markers for pathogenicity.

In vitro interaction of Entamoeba histolytica with collagen induces intracellular formation and release of electron-dense granules (EDG) and stimulation of collagenolytic activity. Purified EDG contain 1.66 U of collagenase per mg of protein. Thus, EDG may participate in tissue destruction during invasive amebiasis. Monoclonal antibodies (MAbs) L1.1 and L7.1 reacted specifically with EDG in enzyme-linked immunosorbent assay (ELISA) and immunofluorescence and immunoelectron microscopy. MAb L7.1 immunoprecipitated three polypeptides with molecular weights of 95,000, 68,000, and 28,000 from lysates of biosynthetically labeled E. histolytica. Both MAbs recognized the pathogenic E. histolytica axenic strains HM1:IMSS, HM38:IMSS, and HK-9 but failed to react in ELISA with Entamoeba moshkovskii, Entamoeba invadens, and E. histolytica-like Laredo. In addition, MAb L7.1 reacted with one E. histolytica isolate from a symptomatic patient but did not react with four of five isolates from asymptomatic patients. EDG antigens were detected by a MAb L7.1-based ELISA in E. histolytica-containing fecal samples from symptomatic, but not asymptomatic, individuals. These results suggest that the EDG antigen detected with MAb L7.1 may be differentially expressed in pathogenic and nonpathogenic E. histolytica.

[Gastrointestinal findings in HIV infection. Clinical aspects, microbiological findings and endoscopic picture]. / Gastrointestinale Befunde bei der HIV-Infektion. Klinik, mikrobiologische Befunde und endoskopisches Erscheinungsbild.

Among 200 hospitalized patients treated for HIV infections there were 98 with gastrointestinal symptoms, independent of the stage of the disease. Only 22 had abnormal stool findings. But histological examination and culture of endoscopically obtained biopsies revealed opportunistic infection in 62, of whom 28 had a cytomegalovirus infection. Mycobacterium avium-intracellulare was found in the gastrointestinal mucosa of 25 patients, but its clinical significance is unclear. In 33 of the 98 patients previously classified as positive for HIV or AIDS-related complex, endoscopic demonstration of an opportunistic infection required amendment of their HIV stage. In over 60% endoscopy revealed mucosal changes. A distinction from Crohn's disease or ulcerative colitis could only be made by histology or exclusion of the causative microorganism. Demonstration of the causative microorganism from the biopsy is thus essential in patients with gastrointestinal symptoms, because specific treatment is in principle possible and successful for some opportunistic infections.