Modification of the clinical course of intestinal microsporidiosis in acquired immunodeficiency syndrome patients by immune status and anti-human immunodeficiency virus therapy

Prevalence and genetic diversity of Enterocytozoon bieneusi in nonhuman primates in Northern and Central China

Background

Enterocytozoon bieneusi is a common enteric pathogen reported in human and many animals. But there are few reports of E. bieneusi in nonhuman primates (NHPs). The aim of this study was to examine the prevalence and molecular characterization of E. bieneusi in NHPs from Northern and Central China.

Results

A total of 299 specimens of NHPs were collected. The overall prevalence rate of E. bieneusi was 9.4% (28/299) in NHPs by ribosomal internal transcribed spacer (ITS) amplification, including 10.0% (16/160) in captive NHPs and 8.6% (12/139) in wild NHPs. In captive NHPs, the infection rate was 9.1% in male, 11.5% in female. Infection rate in juvenile ITS (6.7%) was higher than in the adult ITS (5.6%). In different regions, infection rate in Hubei (14.7%) was higher than in Henan (7.6%) and Beijing (7.9%). Five genotypes were found, including 4 known genotypes (D, HND-Ⅰ, EbpC, SHW2) and a novel genotype named NHP1. Genotype D (8/28) and NHP1 (8/28) were the most prevalent, followed by EbpC (6/28), SHW2 (4/28), and HND-Ⅰ (2/28). All the 5 genotypes belonged to zoonotic Group1.

Conclusion

These findings could deepen our understanding of E. bieneusi prevalence and genotype distribution in NHPs in China. Our study shows that NHPs may be the reservoir of zoonotic E. bieneusi and might present a potential serious threat.

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Enterocytozoon bieneusi was detected in 9.36% fecal specimens of NHPs.

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Four known genotypes (D, HND-Ⅰ, EbpC and SHW2) and a novel genotype NHP1 were detected.

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Genotypes D, HND-Ⅰ, EbpC, SHW2 and NHP1 were classified into zoonotic Group1.

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Nonhuman primates may pose a risk for human transmission.

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.

Treatment of parasitic diarrhea in HIV-infected patients

Parasitic infections responsible for diarrhea have a worldwide distribution, overlapping with AIDS in most countries. Indeed, highly active antiretroviral therapy has markedly reduced the incidence of most parasitic opportunistic infections, but parasite-related diarrhea remains frequent and probably underestimated in developing countries. In this review, we focus on the advances in molecular epidemiology, diagnosis and current treatment of the most prevalent parasitic infections in HIV-infected patients. Most of these parasites are protozoa, whose diagnosis at the laboratory requires some adapted technique and expertise. We highlight the importance of diagnosis and the skill of the laboratory of parasitology, since most parasitic infections responsible for diarrhea in AIDS patients can be treated.

Declining incidence of intestinal microsporidiosis and reduction in AIDS-related mortality following introduction of HAART in Sydney, Australia

Limited data exist regarding the incidence of intestinal microsporidiosis following the introduction of highly active antiretroviral therapy (HAART) in Australia. At St Vincent's Hospital, Sydney, all faecal samples submitted for diarrhoea from HIV-infected patients between 1995 and 2006 underwent screening for microsporidiosis. A total of 3564 patients (7366 faecal specimens) was examined, resulting in 159 patients identified with microsporidiosis. The incidence of microsporidiosis declined from 11% in 1995 to 0% from 2004 onwards. At presentation the majority of patients were severely immunocompromised (median CD4 105 cells/mm(3)), with only 16% of patients on effective HAART. Twenty-four patients (24/76, 32%) died within a median of 22 months following microsporidiosis diagnosis. Significant predictors of AIDS-related mortality at presentation included the level of immunodeficiency and receiving no or ineffective HAART (P<0.05). Patients presenting after 1998 had a significant reduction in the risk of AIDS-related mortality compared with patients presenting before 1998 (hazard ratio 0.27, 95% CI 0.79-0.92). All 52 (68%) surviving patients were on effective HAART, with a median CD4 count 382 cells/mm(3) and HIV RNA of < 50 copies/ml at follow-up (median 4 years). The dramatic decline of intestinal microsporidiosis in our study reconfirms the importance of effective HAART in preventing advanced immunodeficiency, opportunistic infections and associated AIDS-related deaths.

Diarrhea in patients with AIDS

Diarrhea in patients with AIDS is a worldwide problem that can have a devastating impact on quality of life for the patient. Chronic diarrhea, usually defined as at least 4 weeks' duration, is more common in patients with low CD4-positive T-lymphocyte counts, signaling advanced immunosuppression. Some organisms, such as Microsporidia, usually cause diarrhea only in the immunosuppressed; others, such as Cryptosporidium, Salmonella, Shigella, and Campylobacter, which are capable of causing diarrhea in the immunocompetent population, produce more severe or prolonged infections in people living with AIDS. Familiarity with the most common pathogens in the clinician's region will help with diagnosis and treatment. Because treatment options vary widely depending upon the infectious agent, thorough microbiologic evaluation is warranted. A stepped diagnostic approach of stool cultures and specialized microscopy and stains for protozoa, followed by sigmoidoscopy or colonoscopy and duodenoscopy with biopsies for histopathological examination is recommended in all patients with persistent, disabling diarrhea who have a CD4 count of less than 200/mm3, and should be considered for those with higher counts on an individual basis. Treatment, tailored to the specific pathogen, may need to be prolonged in the most severely immunocompromised patients to prevent relapse or recrudescence. For patients taking antiretroviral therapy (especially protease inhibitors) in whom no infectious agent can be found, diarrhea may be due to the medications. Nonspecific antidiarrheal agents should be tried until one that suits the patient is found. The most essential component of any therapeutic strategy for a patient with AIDS-associated diarrhea is restoration of the underlying immunologic defect using highly active antiretroviral therapy.

Enterocytozoon bieneusi (microsporidia) in clinical samples from immunocompetent individuals in Tenerife, Canary Islands, Spain

Microsporidia are newly emerging pathogens of humans and animals, with Enterocytozoon bieneusi being the most common causal agent in human microsporidiosis. To determine the presence of E. bieneusi, 273 clinical samples (40 urine, 156 stools, 37 sputum, 9 bronchial aspirates, 5 bronchial washes and 26 pleural fluids) from immunocompetent patients, mainly suffering diarrhoea or pneumonia, in Tenerife, Canary Islands, Spain were analysed using light microscopy after staining with Weber's chromotrope and by PCR/hybridisation with a specific probe designed to increase the sensitivity of the identification. In this study, detection of E. bieneusi after PCR/hybridisation is reported in 18 (11.54%) of 156 stool samples, 1 (2.5%) of 40 urine samples and 6 (16.22%) of 37 sputum samples. To our knowledge, these are the first reports of E. bieneusi in this subtropical region, showing the increased importance of these parasites as emerging pathogens worldwide.

First detection and genotyping of human-associated microsporidia in pigeons from urban parks

Microsporidia are ubiquitous opportunistic parasites in nature infecting all animal phyla, and the zoonotic potential of this parasitosis is under discussion. Fecal samples from 124 pigeons from seven parks of Murcia (Spain) were analyzed. Thirty-six of them (29.0%) showed structures compatible with microsporidia spores by staining methods. The DNA isolated from 26 fecal samples (20.9%) of microsporidia-positive pigeons was amplified with specific primers for the four most frequent human microsporidia. Twelve pigeons were positive for only Enterocytozoon bieneusi (9.7%), 5 for Encephalitozoon intestinalis (4%), and one for Encephalitozoon hellem (0.8%). Coinfections were detected in eight additional pigeons: E. bieneusi and E. hellem were detected in six animals (4.8%); E. bieneusi was associated with E. intestinalis in one case (0.8%); and E. hellem and E. intestinalis coexisted in one pigeon. No positive samples for Encephalitozoon cuniculi were detected. The internally transcribed spacer genotype could be completed for one E. hellem-positive pigeon; the result was identical to the genotype A1 previously characterized in an E. hellem Spanish strain of human origin. To our knowledge, this is the first time that human-related microsporidia have been identified in urban park pigeons. Moreover, we can conclude that there is no barrier to microsporidia transmission between park pigeons and humans for E. intestinalis and E. hellem. This study is of environmental and sanitary interest, because children and elderly people constitute the main visitors of parks and they are populations at risk for microsporidiosis. It should also contribute to the better design of appropriate prophylactic measures for populations at risk for opportunistic infections.

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.

HIV1 and the gut in the era of highly active antiretroviral therapy

The gut and its gut-associated lymphoid tissue serve as a preferential site for HIV1 entry, active viral replication, reservoir, and HIV-mediated CD4 cell apoptosis. The widespread use of highly active antiretroviral therapy (HAART) has resulted in a significant decrease in the incidence of opportunistic enteric pathogens as a consequence of immune recovery. Nonetheless, patients with advanced HIV1 disease who were recently diagnosed or have poor response to HAART can still suffer from opportunistic infections with pathogens such as Cryptosporidium, microsporidia, Isospora belli, Cyclospora cayetanensis, Mycobacterium avium complex, and cytomegalovirus, among others. This review describes the impact of HIV1 infection on gut immune function, the salient features of the most common opportunistic enteric pathogens and HIV-associated enteropathy, and the effects of immune reconstitution after introduction of HAART.

Intestinal microsporidiosis due to Enterocytozoon bieneusi in elderly human immunodeficiency virus--negative patients from Vigo, Spain

We report what is, to our knowledge, the first study in which microsporidial infection was detected in elderly human immunodeficiency virus (HIV)--negative patients. Of the 60 elderly patients studied, 47 had diarrhea. Intestinal microsporidiosis due to Enterocytozoon bieneusi was diagnosed in 8 patients (17.02%) by use of Weber's chromotrope-based stain and polymerase chain reaction with species-specific primers. The mean age of these 8 patients was 75 years; 7 had chronic diarrhea and 1 had nonchronic diarrhea. Six of the patients with chronic diarrhea had no other pathogens isolated. In our opinion, elderly patients, because of their special immunological characteristics, should be considered a group at risk for the acquisition of intestinal microsporidiosis.

Zoonotic potential of Enterocytozoon bieneusi

The reservoirs and the modes of transmission of the most frequent microsporidial species in humans, Enterocytozoon bieneusi, are still unknown. We have examined fecal samples of 26 humans and 350 animals from 37 species to find 18 samples containing this parasite from humans, cats, pigs, cattle, and a llama. Genotypic characterization of the internal transcribed spacer of the rRNA gene resulted in 14 different genotypes, 6 of them previously undescribed. Phylogenetic analysis revealed the lack of a transmission barrier between E. bieneusi from humans and animals (cats, pigs, and cattle). Thus, E. bieneusi appears to be a zoonotic pathogen.

Infectious diarrhea in human immunodeficiency virus

Chronic HIV-associated diarrhea is currently a field in flux. Improved noninvasive diagnostic tests, improved pathogen-specific regimens, and better empiric therapies may change some of the assumptions used to select algorithms for diagnostic evaluation and management. Any shift in the cause of diarrhea from pathogen-associated to idiopathic or a reduction in the overall incidence of diarrhea would have considerable impact. It is unclear how significant the problem of pathogen relapse in previous responders will become. Existing studies reviewed in this article show that the high diagnostic yield of endoscopy when stool tests are negative, coupled with significantly better outcomes when pathogens are identified, support the current practice of routine endoscopic evaluation. There currently are scant data on the economic impact of HIV-associated diarrhea as it relates to pathogen-specific and empiric therapy in the era of protease inhibitors. Such data would be integral to future evaluation of the impact of diagnostic and therapeutic strategies.

Chemotherapy for patients with multiple parasitic infections

Multiple parasitic infections have become increasingly recognized as a result of improvements in laboratory diagnosis and a growing population of immunocompromised individuals. This review examines the principles of chemotherapy in groupings of multiple infections which are of particular clinical significance.

Emerging and reemerging intestinal protozoa

The intestinal protozoa have gained importance to physicians practicing medicine in the United States, Canada, and Europe during recent years as a result of increasing world travel, the globalization of the world's economy, and the growing number of chronically immunosuppressed people. During the spring of 1996, Cyclospora cayetanensis caused diarrhea in approximately 1500 people exposed to Guatemalan raspberries. This epidemic recurred in 1997, emphasizing the risks of the global economy and food supply on which we depend. In addition to importation of intestinal protozoa from the tropics, AIDS and the increasing use of organ transplants have created a new population of people at risk for chronic infection by ubiquitous protozoa previously not known to cause serious human disease. These infections include cryptosporidiosis, isosporiasis, and microsporidiosis. Finally, Entamoeba histolytica, the etiologic agent of invasive amebiasis, has only recently been recognized to be a distinct species from a nonpathogenic but indistinguishable (by light microscopy) intestinal commensal, Entamoeba dispar. The rapidly changing epidemiology of these intestinal protozoa, as well as new approaches to diagnosis and treatment of these protozoa, are discussed.

Eradication of cryptosporidia and microsporidia following successful antiretroviral therapy

OBJECTIVES

Incidence of opportunistic protozoal infections causing diarrheal illnesses in patients with HIV has decreased since the introduction of highly active antiretroviral therapy (HAART). The objective of this study was to determine whether the parasites, cryptosporidia, and microsporidia were effectively eradicated or only suppressed following treatment.

DESIGN

Six HIV-positive patients with diarrheal symptoms caused by cryptosporidia or microsporidia were prospectively followed up with stool samples and duodenal biopsies. Samples were taken before HAART, between 1 to 3 months, and 6 months post-HAART.

METHODS

Duodenal samples were analyzed using routine histology and transmission electron microscopy. Stool samples were analyzed by both light microscopy and polymerase chain reaction (PCR) techniques.

RESULTS

Patients who responded successfully to HAART eradicated both cryptosporidial and microsporidial organisms. Symptoms improved within 1 month of therapy but complete eradication of the organisms was only observed after 6 months of treatment.

CONCLUSIONS

AIDs-related cryptosporidiosis and microsporidiosis can be cured following successful antiretroviral therapy.

Drug treatment of microsporidiosis

Microsporidia are ubiquitous organisms that are emerging pathogens in humans. These are most likely zoonotic and/or waterborne infections. In the immunosuppressed host, such as those treated with immunosuppressive drugs or infected with human immunodeficiency virus particularly at advanced stages of the disease, microsporidia can produce a wide range of clinical diseases. The most common manifestation is gastrointestinal tract infection; however, encephalitis, ocular infection, sinusitis, myositis and disseminated infection have also been described. In addition, these organisms have been reported in immune competent individuals. Multiple genera are involved in these infections and different organisms can result in distinct clinical pictures. Differences in clinical and parasitologic response to various therapeutic agents have emerged from clinical, as well as in vitro and in vivo studies. Currently there are no precisely defined guidelines for the optimal treatment of microsporidial infections. This article reviews the available data on compounds with in vitro activity and/or in vivo efficacy for microsporidial infections. Copyright 2000 Harcourt Publishers Ltd.

Clinical and diagnostic aspects of intestinal microsporidiosis in HIV-infected patients with chronic diarrhea in Rio de Janeiro, Brazil

The objectives of this study were to determine both the prevalence of microsporidial intestinal infection and the clinical outcome of the disease in a cohort of 40 HIV-infected patients presenting with chronic diarrhea in Rio de Janeiro, Brazil. Each patient, after clinical evaluation, had stools and intestinal fragments examined for viral, bacterial and parasitic pathogens. Microsporidia were found in 11 patients (27.5%) either in stools or in duodenal or ileal biopsies. Microsporidial spores were found more frequently in stools than in biopsy fragments. Samples examined using transmission electron microscopy (n=3) or polymerase chain reaction (n=6) confirmed Enterocytozoon bieneusi as the causative agent. Microsporidia were the only potential enteric pathogens found in 5 of the 11 patients. Other pathogens were also detected in the intestinal tract of 21 patients, but diarrhea remained unexplained in 8. We concluded that microsporidial infection is frequently found in HIV infected persons in Rio de Janeiro, and it seems to be a marker of advanced stage of AIDS.

Eradication of cryptosporidia and microsporidia following successful antiretroviral therapy

OBJECTIVES

Incidence of opportunistic protozoal infections causing diarrheal illnesses in patients with HIV has decreased since the introduction of highly active antiretroviral therapy (HAART). The objective of this study was to determine whether the parasites, cryptosporidia, and microsporidia were effectively eradicated or only suppressed following treatment.

DESIGN

Six HIV-positive patients with diarrheal symptoms caused by cryptosporidia or microsporidia were prospectively followed up with stool samples and duodenal biopsies. Samples were taken before HAART, between 1 to 3 months, and 6 months post-HAART.

METHODS

Duodenal samples were analyzed using routine histology and transmission electron microscopy. Stool samples were analyzed by both light microscopy and polymerase chain reaction (PCR) techniques.

RESULTS

Patients who responded successfully to HAART eradicated both cryptosporidial and microsporidial organisms. Symptoms improved within 1 month of therapy but complete eradication of the organisms was only observed after 6 months of treatment.

CONCLUSIONS

AIDs-related cryptosporidiosis and microsporidiosis can be cured following successful antiretroviral therapy.

Microsporidia: emerging advances in understanding the basic biology of these unique organisms

Microsporidia are long-known parasites of a wide variety of invertebrate and vertebrate hosts. The emergence of these obligate intracellular organisms as important opportunistic pathogens during the AIDS pandemic and the discovery of new species in humans renewed interest in this unique group of organisms. This review summarises recent advances in the field of molecular biology of microsporidia which (i) contributed to the understanding of the natural origin of human-infecting microsporidia, (ii) revealed unique genetic features of their dramatically reduced genome and (iii) resulted in the correction of their phylogenetic placement among eukaryotes from primitive protozoans to highly evolved organisms related to fungi. Microsporidia might serve as new intracellular model organisms in the future given that gene transfer systems will be developed.

Diagnosis of Enterocytozoon bieneusi by PCR in stool samples eluted from filter paper disks

We report a PCR-based assay for the detection of Enterocytozoon bieneusi. We extracted DNA from feces which had been applied to filter paper disks and evaluated four preserving solutions. Infected specimens were identified by electrophoresis of amplicons from concentrated formalin-fixed samples and unconcentrated fresh feces. Our findings demonstrate that this methodology is effective for sample collection, mailing, and diagnosis of this pathogen.

Microsporidiosis in mammals

Microsporidia are small, single-celled, obligately intracellular parasites that have caused significant agricultural losses and interference with biomedical research. Interest in the microsporidia is growing, as these organisms are recognized as agents of opportunistic infections in persons with AIDS and in organ transplant recipients. Microsporidiosis is also being recognized in children and travelers, and furthermore, concern exists about the potential of zoonotic and waterborne transmission of microsporidia to humans. This article reviews the basic biology and epidemiology of microsporidiosis in mammals.

A spore counting method and cell culture model for chlorine disinfection studies of Encephalitozoon syn. Septata intestinalis

The microsporidia have recently been recognized as a group of pathogens that have potential for waterborne transmission; however, little is known about the effects of routine disinfection on microsporidian spore viability. In this study, in vitro growth of Encephalitozoon syn. Septata intestinalis, a microsporidium found in the human gut, was used as a model to assess the effect of chlorine on the infectivity and viability of microsporidian spores. Spore inoculum concentrations were determined by using spectrophotometric measurements (percent transmittance at 625 nm) and by traditional hemacytometer counting. To determine quantitative dose-response data for spore infectivity, we optimized a rabbit kidney cell culture system in 24-well plates, which facilitated calculation of a 50% tissue culture infective dose (TCID(50)) and a minimal infective dose (MID) for E. intestinalis. The TCID(50) is a quantitative measure of infectivity and growth and is the number of organisms that must be present to infect 50% of the cell culture wells tested. The MID is as a measure of a system's permissiveness to infection and a measure of spore infectivity. A standardized MID and a standardized TCID(50) have not been reported previously for any microsporidian species. Both types of doses are reported in this paper, and the values were used to evaluate the effects of chlorine disinfection on the in vitro growth of microsporidia. Spores were treated with chlorine at concentrations of 0, 1, 2, 5, and 10 mg/liter. The exposure times ranged from 0 to 80 min at 25 degrees C and pH 7. MID data for E. intestinalis were compared before and after chlorine disinfection. A 3-log reduction (99.9% inhibition) in the E. intestinalis MID was observed at a chlorine concentration of 2 mg/liter after a minimum exposure time of 16 min. The log(10) reduction results based on percent transmittance-derived spore counts were equivalent to the results based on hemacytometer-derived spore counts. Our data suggest that chlorine treatment may be an effective water treatment for E. intestinalis and that spectrophotometric methods may be substituted for labor-intensive hemacytometer methods when spores are counted in laboratory-based chlorine disinfection studies.

The diagnostic value of electron microscopy in human immunodeficiency virus-positive patients with gastrointestinal disease

BACKGROUND

Our aim was to determine the diagnostic value of electron microscopy in evaluating the etiology of gastrointestinal disease in patients infected with the human immunodeficiency virus (HIV).

METHODS

A retrospective review of electron microscopic and light microscopic results of all HIV-positive patients with gastrointestinal and liver diseases was made during a 3-year period from June 1995 to June 1998.

RESULTS

A total of 145 HIV-positive patients had their electron microscopy specimens reviewed. Of these, 136 were investigated for diarrhea, and the other 9 for increased liver enzymes. Twenty-seven of the 145 (18.6%) HIV-positive patients had a pathogen identified by electron microscopy, compared with only 13 of 145 (9%) identified by light microscopy (P < 0.005). The sensitivity of light microscopy for detecting opportunistic pathogens was 68%. Twenty-one of the 27 (77.8%) patients diagnosed by electron microscopy had microsporidiosis, and the most commonly diagnosed species was Enterocytozoon bieneusi. Light microscopy failed to identify 12 cases of microsporidiosis and 2 cases of leishmaniasis.

CONCLUSIONS

Electron microscopy contributes substantially to the identification of pathogens in HIV-positive patients. Light microscopy failed to identify one of every two pathogens diagnosed by electron microscopy.

Gastrointestinal infections in the immunocompromised host

Infectious diseases of the gastrointestinal tract continue to be an important source of morbidity and mortality. Viruses, bacteria, fungi, and protozoa that infect normal hosts also infect the gastrointestinal tract in immunocompromised hosts. Disease caused by these pathogens may be more severe and more difficult to treat in immunocompromised hosts. In addition, pathogens that rarely cause disease in normal hosts cause significant disease in immunosuppressed hosts. Diagnostic decisions need to take into account expected pathogens and response to therapy. Treatment decisions must be based on the findings of diagnostic procedures; expected pathogens; and recent data suggesting that highly active antiretroviral therapy, with its ability to reconstitute immune function, is an essential component of treatment. This review summarizes the most important developments made in the pathogenesis, clinical presentation, diagnosis, and treatment of gastrointestinal infections in immunocompromised hosts in the past year.

Successful treatment with nitazoxanide of Enterocytozoon bieneusi microsporidiosis in a patient with AIDS

A patient with AIDS and chronic diarrhea caused by Enterocytozoon bieneusi was successfully treated with nitazoxanide, producing a complete clinical and parasitological response, while off of antiviral therapy. This suggests that nitazoxanide may be effective in treating microsporidiosis caused by E. bieneusi, a disease for which there is no established treatment.

Impact of protease inhibitors on the outcome of human immunodeficiency virus-infected patients with chronic diarrhea

OBJECTIVE

The effect of protease inhibitors on the outcome of chronic HIV-related diarrhea is unknown. The aim of this study was to compare the response to treatment of chronic HIV-related diarrhea, recurrence of diarrhea, and survival in a large cohort of individuals taking protease inhibitors to the outcome in similar patients not receiving protease inhibitors.

METHODS

We reviewed the medical records of all patients referred between October 1993 and October 1996 at Bellevue Hospital for endoscopic evaluation of chronic HIV-related diarrhea after negative stool examination. Only patients presenting after December 1995 received protease inhibitor therapy. Follow-up data were obtained from chart review and direct telephone contact. The success of antidiarrheal therapy was compared between protease inhibitor and nonprotease inhibitor groups for patients receiving pathogen-specific therapy and for those with no pathogens found on endoscopy.

RESULTS

Two hundred eighty-two of 307 patients evaluated for chronic diarrhea were followed for a mean of 69.9+/-34.1 weeks. Patients receiving protease inhibitors had a significantly higher rate of successful response to antidiarrheal therapy (62.0% vs 33.5%, p < 0.001). Protease inhibitors were associated with a significant decrease in stool frequency (4.8+/-4.5 vs 3.4+/-4.6 bowel movements per day, p = 0.01), an increase in weight (2.4+/-5.9 vs -1.6+/-6.2 kg, p < 0.001), a decrease in recurrence of diarrhea (34.8% vs 15.3%, p = 0.02), and a longer mean survival (148 vs 118 weeks, p = 0.002).

CONCLUSIONS

Protease inhibitors significantly improve the outcome of antidiarrheal therapy and survival in patients with chronic HIV-associated diarrhea.

Cryptosporidia and microsporidia--waterborne diseases in the immunocompromised host

Cryptosporidia and microsporidia are emerging parasitic pathogens in immunocompetent and immunocompromised individuals. Cryptosporidium infects several wild and domestic animals that excrete oocysts into the environment and contaminated water represents the major source of infection for humans. Waterborne transmission of Cryptosporidium is a major risk for humans and appropriate measures have to be taken to protect immunocompetent and immunocompromised individuals to become infected. For microsporidia, the sources and ways of transmission are not well documented. Although several animal hosts have been identified recently, the relevant reservoirs of human microsporidia are still unknown. Also, the routes of spreading are unknown. Is microsporidiosis a zoonotic disease that will be transmitted through close contact with infected animals or is contaminated surface water responsible for transmission and represents a relevant reservoir? This review is designed to give information on these two emerging intestinal parasites in a format that will be useful to clinical microbiologists, physicians interested in infectious diseases, and public health personnel.

Molecular techniques for detection, species differentiation, and phylogenetic analysis of microsporidia

Microsporidia are obligate intracellular protozoan parasites that infect a broad range of vertebrates and invertebrates. These parasites are now recognized as one of the most common pathogens in human immunodeficiency virus-infected patients. For most patients with infectious diseases, microbiological isolation and identification techniques offer the most rapid and specific determination of the etiologic agent. This is not a suitable procedure for microsporidia, which are obligate intracellular parasites requiring cell culture systems for growth. Therefore, the diagnosis of microsporidiosis currently depends on morphological demonstration of the organisms themselves. Although the diagnosis of microsporidiosis and identification of microsporidia by light microscopy have greatly improved during the last few years, species differentiation by these techniques is usually impossible and transmission electron microscopy may be necessary. Immunfluorescent-staining techniques have been developed for species differentiation of microsporidia, but the antibodies used in these procedures are available only at research laboratories at present. During the last 10 years, the detection of infectious disease agents has begun to include the use of nucleic acid-based technologies. Diagnosis of infection caused by parasitic organisms is the last field of clinical microbiology to incorporate these techniques and molecular techniques (e.g., PCR and hybridization assays) have recently been developed for the detection, species differentiation, and phylogenetic analysis of microsporidia. In this paper we review human microsporidial infections and describe and discuss these newly developed molecular techniques.