Molecular diagnosis of an Enterocytozoon bieneusi human genotype C infection in a moderately immunosuppressed human immunodeficiency virus seronegative liver-transplant recipient with severe chronic diarrhea

A Simian Immunodeficiency Virus-Infected Macaque Model of Enterocytozoon bieneusi Infection

Microsporidiosis caused by Enterocytozoon bieneusi is a common opportunistic infection in patients with HIV/AIDS and those on immunosuppressive therapy. A significant loss of mucosal or peripheral CD4+ T cells and subsequent dysfunction of the intestinal immune system may be responsible for the development of chronic microsporidiosis in these patients. We have used the Simian immunodeficiency virus (SIV)-infected macaque model to investigate this relationship. To establish the course of E. bieneusi infection in SIV-infected animals, four SIV-infected animals were experimentally challenged with E. bieneusi when their CD4+ counts dropped to less than 300 cells/μL of blood. Analysis of fecal samples by nested polymerase chain reaction revealed that three out of four E. bieneusi-infected macaques continued to shed spores for 7-24 months after infection, an indication of chronic microsporidiosis. Four other SIV-infected macaques, after having an initial negative phase, spontaneously acquired E. bieneusi infection when their CD4+ counts dropped to less than 600 cells/μL of blood and shed spores for 8-19 months. The shedding of E. bieneusi spores in the feces increased relative to decrease in peripheral blood CD4+ T cell numbers. Gut biopsies were obtained before and after challenge to phenotype the mucosal lymphocyte subsets using flow cytometry. The immunophenotypic analysis showed no restoration of CD4+ T cells after E. bieneusi infection in the intestinal cells. A slight increase in the percentage population of CD4+ T cells in peripheral blood did not have any effect on the control of E. bieneusi infection in the SIV-infected macaques. These preliminary studies demonstrate that SIV-infected macaques develop chronic E. bieneusi infections as their CD4+ counts dropped to below 300 cells/μL of blood.

A Perspective on the Molecular Identification, Classification, and Epidemiology of Enterocytozoon bieneusi of Animals

The microsporidian Enterocytozoon bieneusi is an obligate intracellular pathogen that causes enteric disease (microsporidiosis) in humans and has been recorded in a wide range of animal species worldwide. The transmission of E. bieneusi is direct and likely occurs from person to person and from animal to person via the ingestion of spores in water, food, or the environment. The identification of E. bieneusi is usually accomplished by molecular means, typically using the sequence of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA. Currently, ~820 distinct genotypes of E. bieneusi have been recorded in at least 210 species of vertebrates (mammals, birds, reptiles, and amphibians) or invertebrates (insects and mussels) in more than 50 countries. In this chapter, we provide a perspective on (1) clinical aspects of human microsporidiosis; (2) the genome and DNA markers for E. bieneusi as well as molecular methods for the specific and genotypic identification of E. bieneusi; (3) epidemiological aspects of E. bieneusi of animals and humans, with an emphasis on the genotypes proposed to be zoonotic, human-specific, and animal-specific; and (4) future research directions to underpin expanded molecular studies to better understand E. bieneusi and microsporidiosis.

Microsporidiosis in Humans

Microsporidia are obligate intracellular pathogens identified ∼150 years ago as the cause of pébrine, an economically important infection in silkworms. There are about 220 genera and 1,700 species of microsporidia, which are classified based on their ultrastructural features, developmental cycle, host-parasite relationship, and molecular analysis. Phylogenetic analysis suggests that microsporidia are related to the fungi, being grouped with the Cryptomycota as a basal branch or sister group to the fungi. Microsporidia can be transmitted by food and water and are likely zoonotic, as they parasitize a wide range of invertebrate and vertebrate hosts. Infection in humans occurs in both immunocompetent and immunodeficient hosts, e.g., in patients with organ transplantation, patients with advanced human immunodeficiency virus (HIV) infection, and patients receiving immune modulatory therapy such as anti-tumor necrosis factor alpha antibody. Clusters of infections due to latent infection in transplanted organs have also been demonstrated. Gastrointestinal infection is the most common manifestation; however, microsporidia can infect virtually any organ system, and infection has resulted in keratitis, myositis, cholecystitis, sinusitis, and encephalitis. Both albendazole and fumagillin have efficacy for the treatment of various species of microsporidia; however, albendazole has limited efficacy for the treatment of Enterocytozoon bieneusi. In addition, immune restoration can lead to resolution of infection. While the prevalence rate of microsporidiosis in patients with AIDS has fallen in the United States, due to the widespread use of combination antiretroviral therapy (cART), infection continues to occur throughout the world and is still seen in the United States in the setting of cART if a low CD4 count persists.

Enterocytozoon bieneusi of animals-With an 'Australian twist'

Enterocytozoon bieneusi is a microsporidian microorganism that causes intestinal disease in animals including humans. E. bieneusi is an obligate intracellular pathogen, typically causing severe or chronic diarrhoea, malabsorption and/or wasting. Currently, E. bieneusi is recognised as a fungus, although its exact classification remains contentious. The transmission of E. bieneusi can occur from person to person and/or animals to people. Transmission is usually via the faecal-oral route through E. bieneusi spore-contaminated water, environment or food, or direct contact with infected individuals. Enterocytozoon bieneusi genotypes are usually identified and classified by PCR-based sequencing of the internal transcribed spacer region (ITS) of nuclear ribosomal DNA. To date, ~600 distinct genotypes of E. bieneusi have been recorded in ~170 species of animals, including various orders of mammals and reptiles as well as insects in >40 countries. Moreover, E. bieneusi has also been found in recreational water, irrigation water, and treated raw- and waste-waters. Although many studies have been conducted on the epidemiology of E. bieneusi, prevalence surveys of animals and humans are scant in some countries, such as Australia, and transmission routes of individual genotypes and related risk factors are poorly understood. This article/chapter reviews aspects of the taxonomy, biology and epidemiology of E. bieneusi; the diagnosis, treatment and prevention of microsporidiosis; critically appraises the naming system for E. bieneusi genotypes as well as the phylogenetic relationships of these genotypes; provides new insights into the prevalence and genetic composition of E. bieneusi populations in animals in parts of Australia using molecular epidemiological tools; and proposes some areas for future research in the E. bieneusi/microsporidiosis field.

A Case of Intestinal Microsporidiosis in a Renal Transplant Recipient

Post-renal transplant diarrhea is a common clinical presentation. An extensive list of potential etiology adds to the diagnostic dilemma. In cases of prolonged or intractable diarrhea, invasive tests are often performed. Intestinal microsporidia can be diagnosed with simple non-invasive stool polymerase chain reaction (PCR). Based on this case, we propose an easy to follow flow chart and present a literature review on post-renal transplant diarrhea. Further multicenter validation testing is required for the proposed flow chart.

Solid Organ Transplant and Parasitic Diseases: A Review of the Clinical Cases in the Last Two Decades

The aim of this study was to evaluate the occurrence of parasitic infections in solid organ transplant (SOT) recipients. We conducted a systematic review of literature records on post-transplant parasitic infections, published from 1996 to 2016 and available on PubMed database, focusing only on parasitic infections acquired after SOT. The methods and findings of the present review have been presented based on the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) checklist. From data published in the literature, the real burden of parasitic infections among SOT recipients cannot really be estimated. Nevertheless, publications on the matter are on the increase, probably due to more than one reason: (i) the increasing number of patients transplanted and then treated with immunosuppressive agents; (ii) the “population shift” resulting from immigration and travels to endemic areas, and (iii) the increased attention directed to diagnosis/notification/publication of cases. Considering parasitic infections as emerging and potentially serious in their evolution, additional strategies for the prevention, careful screening and follow-up, with a high level of awareness, identification, and pre-emptive therapy are needed in transplant recipients.

Intestinal microsporidiosis in Strasbourg from 2014 to 2016: emergence of an Enterocytozoon bieneusi genotype of Asian origin

Microsporidia cause opportunistic infections in highly immunodeficient individuals. Few studies on the epidemiology of these infections have been conducted in France. Between 2014 and 2016, we undertook a study to estimate the prevalence and circulating genotypes of this fungus-related micro-organism among the population of Strasbourg University Hospital. Samples were collected from hospitalized patients and analyzed using microscopy and molecular assays. Strains from positive subjects were sequenced for genotyping. Only 7/661 patients (1.1%) were positive for microsporidia, and the only species identified was Enterocytozoon bieneusi. Two patients presented immunodeficiency linked to AIDS, and five transplant recipients presented immunodeficiency linked to immunosuppressive therapies. Only five patients received specific antimicrosporidial treatment, but clinical outcomes were good in all cases. We identified four genotypes: A and D in patients with AIDS, and C and S9 in transplant recipients. To date, genotype S9 has been described only once. This genotype is similar to those found in farm animals in China. Because some of these animals have been introduced to Central Europe, we postulate that this genotype might be of Asian origin. Thus, genotyping microsporidial strains may be of epidemiological and clinical interest to identify potential outbreak sources depending on the infecting strains.

Microsporidia and coccidia as causes of persistence diarrhea among liver transplant children: incidence rate and species/genotypes

We determined species/genotype(s) of enteric microsporidia and coccidia causing diarrhea among 44 liver transplant children in Shiraz Nemazee hospital using acid-fast-trichrome staining and polymerase chain reaction-sequencing techniques. Enterocytozoon bieneusi (genotype D), Cryptosporidium (parvum and meleagridis) were detected in 6.81% and 11.36% of the children, respectively.

Molecular epidemiologic characterization of Enterocytozoon bieneusi in HIV-infected persons in Benin City, Nigeria

Molecular characterization of Enterocytozoon bieneusi has led to better understanding of microsporidiosis transmission in humans. This study aimed to detect and genotype E. bieneusi in human immunodeficiency virus (HIV)-infected persons. Stool specimens were collected from 463 HIV-infected patients and analyzed for E. bieneusi by polymerase chain reaction (PCR) and DNA sequence analysis of the internal transcribed spacer. E. bieneusi was detected in 77 HIV patients. CD4 cell counts < 200 cells/μL was associated with E. bieneusi infection (P = 0.09). E. bieneusi was significantly associated with weight loss (P < 0.0001), diarrhea (P = 0.006), fever (P < 0.0001), not being married (P < 0.0001), and flush type of toilet (P = 0.0007). Six known genotypes of D, A, IV, CAF2, EbpA, and Peru 8 in 31, 22, 14, 2, 1, and 1 patients, respectively, five novel genotypes of E. bieneusi, and one infection with mixed genotypes were observed in this study. Three of the novel genotypes were genetically distant to the genotypes commonly found in humans.

Identification and characterization of microsporidia from fecal samples of HIV-positive patients from Lagos, Nigeria

Background

Microsporidia are obligate intracellular parasites that infect a broad range of vertebrates and invertebrates. They have been increasingly recognized as human pathogens in AIDS patients, mainly associated with a life-threatening chronic diarrhea and systemic disease. However, to date the global epidemiology of human microsporidiosis is poorly understood, and recent data suggest that the incidence of these pathogens is much higher than previously reported and may represent a neglected etiological agent of more common diseases indeed in immunocompetent individuals. To contribute to the knowledge of microsporidia molecular epidemiology in HIV-positive patients in Nigeria, the authors tested stool samples proceeding from patients with and without diarrhea.

Methodology/Principal Findings

Stool samples from 193 HIV-positive patients with and without diarrhea (67 and 126 respectively) from Lagos (Nigeria) were investigated for the presence of microsporidia and Cryptosporidium using Weber’s Chromotrope-based stain, Kinyoun stain, IFAT and PCR. The Weber stain showed 45 fecal samples (23.3%) with characteristic microsporidia spores, and a significant association of microsporidia with diarrhea was observed (O.R.  = 18.2; CI: 95%). A similar result was obtained using Kinyoun stain, showing 44 (31,8%) positive samples with structures morphologically compatible with Cryptosporidium sp, 14 (31.8%) of them with infection mixed with microsporidia. The characterization of microsporidia species by IFAT and PCR allowed identification of Enterocytozoon bieneusi, Encephalitozoon intestinalis and E. cuniculi in 5, 2 and 1 samples respectively. The partial sequencing of the ITS region of the rRNA genes showed that the three isolates of E.bieneusi studied are included in Group I, one of which bears the genotype B.

Conclusions/Significance

To our knowledge, this is the first report of microsporidia characterization in fecal samples from HIV-positive patients from Lagos, Nigeria. These results focus attention on the need to include microsporidial diagnosis in the management of HIV/AIDS infection in Nigeria, at the very least when other more common pathogens have not been detected.

Microsporidia infection in a mexican kidney transplant recipient

Microorganisms of the microsporidia group are obligated intracellular protozoa that belong to the phylum Microspora; currently they are considered to be related or belong to the fungi reign. It is considered an opportunistic infection in humans, and 14 species belonging to 8 different genera have been described. Immunocompromized patients such as those infected with human immunodeficiency virus (HIV), also HIV serum-negative asymptomatic patients, with poor hygienic conditions, and recipients of bone marrow or solid organ transplantation are susceptible to develop deinfection. Sixty transplanted patients with renal microsporidia infection have been reported worldwide. The aim of this paper is to inform about the 2nd case of kidney transplant and microsporidia infection documented in Mexico.

First reported foodborne outbreak associated with microsporidia, Sweden, October 2009

Microsporidia are spore-forming intracellular parasites that infrequently cause disease in immunocompetent persons. This study describes the first report of a foodborne microsporidiosis outbreak which affected persons visiting a hotel in Sweden. Enterocytozoon bieneusi was identified in stool samples from 7/11 case-patients, all six sequenced samples were genotype C. To confirm that this was not a chance finding, 19 stool samples submitted by healthy persons from a comparable group who did not visit the hotel on that day were tested; all were negative for microsporidia. A retrospective cohort study identified 135 case-patients (attack rate 30%). The median incubation period was 9 days. Consumption of cheese sandwiches [relative risk (RR) 4·1, 95% confidence interval (CI) 1·4–12·2] and salad (RR 2·1, 95% CI 1·1–4) were associated with illness. Both items contained pre-washed, ready-to-eat cucumber slices. Microsporidia may be an under-reported cause of gastrointestinal outbreaks; we recommend that microsporidia be explored as potential causative agents in food- and waterborne outbreaks, especially when no other organisms are identified.

First cases of microsporidiosis in transplant recipients in Spain and review of the literature

Microsporidia are currently considered emerging pathogens responsible for life-threatening infections in organ transplant recipients. Here, we describe the first cases of intestinal microsporidiosis by Enterocytozoon bieneusi genotype D in two non-HIV-infected renal transplant recipients from Spain. Previously reported cases of microsporidiosis in organ transplant recipients have also been reviewed, highlighting the necessity of considering organ transplant recipients a risk group for microsporidiosis. A systematic search for these parasites is recommended in cases of persistent diarrhea and in the differential diagnosis of other syndromes, such as chronic fever of unknown etiology.

Parasitic infections in solid organ transplant recipients

Parasitic infections are an uncommon but potentially severe complication in solid organ transplant (SOT) recipients. An increase in donors who have emigrated from tropical areas and more transplant recipients traveling to endemic areas have led to a rise in parasitic infections reported among SOT recipients. Clinicians should include these infections in their differential diagnosis and promote adherence to preventive measures in SOT recipients.

Clinical significance of enteric protozoa in the immunosuppressed human population

Globally, the number of immunosuppressed people increases each year, with the human immunodeficiency virus (HIV) pandemic continuing to spread unabated in many parts of the world. Immunosuppression may also occur in malnourished persons, patients undergoing chemotherapy for malignancy, and those receiving immunosuppressive therapy. Components of the immune system can be functionally or genetically abnormal as a result of acquired (e.g., caused by HIV infection, lymphoma, or high-dose steroids or other immunosuppressive medications) or congenital illnesses, with more than 120 congenital immunodeficiencies described to date that either affect humoral immunity or compromise T-cell function. All individuals affected by immunosuppression are at risk of infection by opportunistic parasites (such as the microsporidia) as well as those more commonly associated with gastrointestinal disease (such as Giardia). The outcome of infection by enteric protozoan parasites is dependent on absolute CD4(+) cell counts, with lower counts being associated with more severe disease, more atypical disease, and a greater risk of disseminated disease. This review summarizes our current state of knowledge on the significance of enteric parasitic protozoa as a cause of disease in immunosuppressed persons and also provides guidance on recent advances in diagnosis and therapy for the control of these important parasites.

Microsporidiosis in solid organ transplant recipients: two Enterocytozoon bieneusi cases and review

Microsporidiosis first came to prominence as an opportunistic infection in patients with acquired immunodeficiency syndrome. Microsporidia are now emerging pathogens responsible for severe diarrhea during solid organ transplantation. Two main clinical entities can be identified: infection by Enterocytozoon bieneusi, causing diarrhea with limited treatment options; and infection by Encephalitozoon intestinalis, which may disseminate and usually responds to albendazole treatment. We describe here 2 cases of microsporidiosis caused by E. bieneusi in a renal and a liver transplant recipient, respectively, in whom complete clinical efficacy of a short course of fumagillin therapy was obtained. Long-term microbiological eradication was assessed using classical methods and monitored using a real-time quantitative polymerase chain reaction-based method. Both patients experienced drug-induced thrombocytopenia, which resolved after withdrawal of the treatment. We also review the 18 other previously reported cases of microsporidiosis in transplant recipients. In case of persistent diarrhea in solid organ transplant patients, microsporidiosis should be considered. Based on the present experience, treating E. bieneusi infection with 7 days of fumagillin therapy is adequate to eradicate E. bieneusi in this context.

Monoclonal antibodies against Enterocytozoon bieneusi of human origin

Enterocytozoon bieneusi is clinically the most significant among the microsporidia infecting humans, causing chronic diarrhea, wasting, and cholangitis in individuals with human immunodeficiency virus/AIDS. The lack of immune reagents is largely due to the absence of methods for laboratory propagation of E. bieneusi. We recently described a procedure for the concentration and purification of spores from diarrheic stool of infected humans. Purified spores were used to immunize mice for production and screening of monoclonal antibodies (MAbs) against E. bieneusi. The eight immunoglobulin M MAbs generated and fully characterized did not cross-react with other human microsporidia or with other microorganisms normally present in stool. One of the MAbs, 2G4, reacted with E. bieneusi spores in stools from monkeys and humans, without background fluorescence, which makes it an ideal diagnostic reagent. It also recognizes intracellular stages of the parasite and will be suitable for determining tissue distribution of E. bieneusi in infected hosts. At least two immunodominant antigens of E. bieneusi of 33,000 and 35,000 Da exist, which were recognized by rabbit and mouse antisera. The availability of MAbs against E. bieneusi will simplify considerably the diagnosis of this infection in humans and will provide tools for epidemiologic investigations regarding the true prevalence of the infection in various human and mammalian populations and the environmental sources of infection.

Production and characterization of monoclonal antibodies against Enterocytozoon bieneusi purified from rhesus macaques

Enterocytozoon bieneusi spores derived from rhesus macaque feces were purified by serial salt-Percoll-sucrose-iodixanol centrifugation, resulting in two bands with different specific densities of 95.6% and 99.5% purity and with a recovery efficiency of 10.8%. An ultrastructural examination revealed typical E. bieneusi spores. Twenty-six stable hybridomas were derived from BALB/c mice immunized with spores and were cloned twice by limiting dilution or growth on semisolid medium. Four monoclonal antibodies (MAbs), reacting exclusively with spores, were further characterized. These MAbs specifically reacted with spores present in stools of humans and macaques, as visualized by immunofluorescence, and with spore walls, as visualized by immunoelectron microscopy. A blocking enzyme-linked immunosorbent assay and Western blotting revealed that the epitope recognized by 8E2 was different from those recognized by 7G2, 7H2, and 12G8, which identified the same 40-kDa protein. These MAbs will be valuable tools for diagnostics, for epidemiological investigations, for host-pathogen interaction studies, and for comparative genomics and proteomics.

Zoonotic potential of the microsporidia

Microsporidia are long-known parasitic organisms of almost every animal group, including invertebrates and vertebrates. Microsporidia emerged as important opportunistic pathogens in humans when AIDS became pandemic and, more recently, have also increasingly been detected in otherwise immunocompromised patients, including organ transplant recipients, and in immunocompetent persons with corneal infection or diarrhea. Two species causing rare infections in humans, Encephalitozoon cuniculi and Brachiola vesicularum, had previously been described from animal hosts (vertebrates and insects, respectively). However, several new microsporidial species, including Enterocytozoon bieneusi, the most prevalent human microsporidian causing human immunodeficiency virus-associated diarrhea, have been discovered in humans, raising the question of their natural origin. Vertebrate hosts are now identified for all four major microsporidial species infecting humans (E. bieneusi and the three Encephalitozoon spp.), implying a zoonotic nature of these parasites. Molecular studies have identified phenotypic and/or genetic variability within these species, indicating that they are not uniform, and have allowed the question of their zoonotic potential to be addressed. The focus of this review is the zoonotic potential of the various microsporidia and a brief update on other microsporidia which have no known host or an invertebrate host and which cause rare infections in humans.

Purification of Enterocytozoon bieneusi from stools and production of specific antibodies

Enterocytozoon bieneusi is clinically the most significant of the microsporidia in humans, causing chronic diarrhea wasting and cholangitis in individuals with human immunodeficiency virus infection and AIDS. Little progress on this infection has been made because of the inability to propagate E. bieneusi in vitro and in vivo, which limits the source of parasite spores to the stools of infected human patients. Given the size and shape of the E. bieneusi spores (1.1 to 1.6 by 0.7 to 1.0 microm) and the lack of specific immune reagents, the identification and purification of large quantities of spores from feces are technically challenging. Consequently, diagnosis relies entirely on PCR, a labor-intensive approach that requires highly skilled personnel. We describe a method for the purification of E. bieneusi spores from human stools and the production of rabbit-specific antisera. Spores were purified by a combination of isopycnic Percoll gradient centrifugation and continuous sucrose gradient centrifugation. Specific polyclonal antibodies raised in mice and rabbits reacted by indirect immunofluorescence with E. bieneusi but not with Encephalitozoon spp., Candida albicans, Staphylococcus aureus, Escherichia coli, or other forms present in human stools.

Disseminated microsporidiosis in a pancreas/kidney transplant recipient

Human microsporidiosis has been described most commonly in patients with acquired immunodeficiency syndrome and only rarely in those with other forms of immunosuppression. Only 11 cases of microsporidiosis have been reported previously in solid transplant recipients. To our knowledge, this is the first report to describe a case of microsporidiosis in a pancreas/kidney transplant recipient in whom multi-organ system dissemination was observed. This infection was not detected until postmortem examination of stained tissue sections revealed microsporidian spores that were identified as Encephalitozoon species by transmission electron microscopy. It is suspected that leakage from the duodenal anastomosis to the bladder may have contributed to the dissemination of this infection.