Cystoisospora belli infections in humans: the past 100 years

Metabarcoding study of potential pathogens and zoonotic risks associated with dog feces in Seoul, South Korea

BACKGROUND

A significant portion of South Korea's population, approximately a quarter, owns pets, with dogs being the most popular choice among them. However, studies analyzing the fecal organism communities of dogs in South Korea are lacking, and limited efforts have been exerted to identify pathogens with potential zoonotic implications. Therefore, this study aimed to investigate potential pathogens using metabarcoding analysis and evaluate the risk of zoonotic diseases in dog feces in Seoul, South Korea.

METHODOLOGY

Fecal samples were collected from both pet and stray dogs in the Mapo district of Seoul. Next-generation sequencing (NGS) was utilized, employing 16S rRNA amplicon sequencing to identify prokaryotic pathogens, and 18S rRNA amplicon sequencing for eukaryotic pathogens. The data obtained from the QIIME2 pipeline were subjected to various statistical analyses to identify different putative pathogens and their compositions.

PRINCIPAL FINDINGS

Significant variations in microbiota composition were found between stray and pet dogs, and putative prokaryotic and eukaryotic pathogens were identified. The most prevalent putative bacterial pathogens were Fusobacterium, Helicobacter, and Campylobacter. The most prevalent putative eukaryotic pathogens were Giardia, Pentatrichomonas, and Cystoisospora. Interestingly, Campylobacter, Giardia, and Pentatrichomonas were found to be significantly more prevalent in stray dogs than in pet dogs. The variation in the prevalence of potential pathogens in dog feces could be attributed to environmental factors, including dietary variances and interactions with wildlife, particularly in stray dogs. These factors likely contributed to the observed differences in pathogen occurrence between stray and pet dogs.

CONCLUSIONS/SIGNIFICANCE

This study offers valuable insights into the zoonotic risks associated with dog populations residing in diverse environments. By identifying and characterizing putative pathogens in dog feces, this research provides essential information on the impact of habitat on dog-associated pathogens, highlighting the importance of public health planning and zoonotic risk management.

Intestinal protozoa in returning travellers: a GeoSentinel analysis from 2007 to 2019

BACKGROUND

Prolonged diarrhoea is common amongst returning travellers and is often caused by intestinal protozoa. However, the epidemiology of travel-associated illness caused by protozoal pathogens is not well described.

METHODS

We analysed records of returning international travellers with illness caused by Giardia duodenalis, Cryptosporidium spp., Cyclospora cayetanensis or Cystoisospora belli, reported to the GeoSentinel Network during January 2007-December 2019. We excluded records of travellers migrating, with an unascertainable exposure country, or from GeoSentinel sites that were not located in high-income countries.

RESULTS

There were 2517 cases, 82.3% giardiasis (n = 2072), 11.4% cryptosporidiosis (n = 287), 6.0% cyclosporiasis (n = 150) and 0.3% cystoisosporiasis (n = 8). Overall, most travellers were tourists (64.4%) on long trips (median durations: 18-30 days). Cryptosporidiosis more frequently affected people < 18 years (13.9%) and cyclosporiasis affected people ≥ 40 years (59.4%). Giardiasis was most frequently acquired in South Central Asia (45.8%) and sub-Saharan Africa (22.6%), cryptosporidiosis in sub-Saharan Africa (24.7%) and South-Central Asia (19.5%), cyclosporiasis in South East Asia (31.3%) and Central America (27.3%), and cystoisosporiasis in sub-Saharan Africa (62.5%). Cyclosporiasis cases were reported from countries of uncertain endemicity (e.g. Cambodia) or in countries with no previous evidence of this parasite (e.g. French Guiana). The time from symptom onset to presentation at a GeoSentinel site was the longest amongst travellers with giardiasis (median: 30 days). Over 14% of travellers with cryptosporidiosis were hospitalized.

CONCLUSIONS

This analysis provides new insights into the epidemiology and clinical significance of four intestinal protozoa that can cause morbidity in international travellers. These data might help optimize pretravel advice and post-travel management of patients with travel-associated prolonged gastrointestinal illnesses. This analysis reinforces the importance of international travel-related surveillance to identify sentinel cases and areas where protozoal infections might be undetected or underreported.

Microscopic and Molecular Identification of Cyclospora cayetanensis and Cystoisospora belli in HIV-Infected People in Tabriz, Northwest of Iran

Opportunistic pathogens such as Cryptosporidium, Cystoisospora belli, and Cyclospora cayetanensis cause various gastrointestinal and non-digestive disorders in people with HIV/AIDS. These symptoms are especially severe in HIV-infected people who have a CD4+ count of less than 200 cells/mL. This study aimed to determine the prevalence of C. belli and C. cayetanensis infections among people living with HIV in Tabriz, northwest of Iran. This descriptive study was performed on 137 people with HIV who had been referred to behavioral disease counseling centers in Tabriz. Then, after receiving written consent, fecal samples were collected and evaluated for the detection of parasitic infections using direct methods and modified acid fast staining, as well as polymerase chain reaction (PCR).From the 137 fecal samples collected (98 males and 39 females, between 20 and 40 years old), 1.5% were positive for C. cayetanensis and 2.9% were positive for C. belli. Due to the prevalence of C. cayetanensis and C. belli in people with HIV in Tabriz, essential measures, including personal hygiene training for infection control and prevention, seem necessary.

Protozoan predation as a driver of diversity and virulence in bacterial biofilms

Protozoa are eukaryotic organisms that play a crucial role in nutrient cycling and maintaining balance in the food web. Predation, symbiosis and parasitism are three types of interactions between protozoa and bacteria. However, not all bacterial species are equally susceptible to protozoan predation as many are capable of defending against predation in numerous ways and may even establish either a symbiotic or parasitic life-style. Biofilm formation is one such mechanism by which bacteria can survive predation. Structural and chemical components of biofilms enhance resistance to predation compared to their planktonic counterparts. Predation on biofilms gives rise to phenotypic and genetic heterogeneity in prey that leads to trade-offs in virulence in other eukaryotes. Recent advances, using molecular and genomics techniques, allow us to generate new information about the interactions of protozoa and biofilms of prey bacteria. This review presents the current state of the field on impacts of protozoan predation on biofilms. We provide an overview of newly gathered insights into (i) molecular mechanisms of predation resistance in biofilms, (ii) phenotypic and genetic diversification of prey bacteria, and (iii) evolution of virulence as a consequence of protozoan predation on biofilms.

Intestinal Parasitic Infections in 2023

Intestinal parasites include intestinal protozoa and intestinal helminths. Intestinal parasitic infections (IPIs) pose a global health problem affecting over one billion people worldwide. Although these infections are predominantly seen in the developing world, they are frequently seen in the developed countries, particularly in immunocompromised patients. Patients' clinical presentations generally include diarrhea, dysentery, abdominal pain, nausea, vomiting, nutritional deficiency, iron deficiency anemia, anal and perianal itching, and rarely intestinal obstruction. The intestinal parasites have similarities in their mode of transmission and life cycle. The stool test is the primary way of diagnosing IPIs. Treatment is given with various anti-parasitic agents. However, appropriate preventive measures are essential for successfully controlling the IPIs.

Development of a new multiplex PCR to detect fecal coccidian parasite

BACKGROUND

Cryptosporidium spp., Cystoisospora belli and Cyclospora cayetanensis are common intestinal coccidian parasites causing gastroenteritis. The clinical presentation caused by each parasite is indistinguishable from each other. Uniplex polymerase chain reaction (PCR) for these three groups of intestinal coccidian parasites was developed by us in our laboratory. Thereafter, we planned to develop a single-run multiplex polymerase chain reaction (mPCR) assay to detect Cryptosporidium spp., C. belli and C. cayetanensis simultaneously from a stool sample and described it here as coccidian mPCR.

METHODS

New primers for C. belli and C. cayetanensis were designed and uniplex PCRs were standardized. The coccidian mPCR was standardized with known positive DNA control isolates. It was validated with 58 known positive and 58 known negative stool samples, which were previously identified by uniplex PCR.

RESULTS

The coccidian mPCR was standardized with earlier primers designed by us for Cryptosporidium spp. and C. cayetanensis, and a newly designed primer for the internal transcribed spacer-1 (ITS-1) gene for C. belli. The coccidian mPCR was 92.1% sensitive for Cryptosporidium spp., and 100% sensitive for C. belli and C. cayetanensis each, when tested on 116 known samples. It was 100% specific for all intestinal coccidian parasites. Two representative PCR products of the newly designed ITS-1 primer for C. belli were sequenced and submitted to the GenBank, which best match with the sequences of C. belli.

CONCLUSION

A highly sensitive, specific, cost-effective, indigenous, single-run coccidian mPCR has been developed, which can simultaneously detect Cryptosporidium spp., C. belli and C. cayetanensis.

The Tubulin Superfamily in Apicomplexan Parasites

Microtubules and specialized microtubule-containing structures are assembled from tubulins, an ancient superfamily of essential eukaryotic proteins. Here, we use bioinformatic approaches to analyze features of tubulins in organisms from the phylum Apicomplexa. Apicomplexans are protozoan parasites that cause a variety of human and animal infectious diseases. Individual species harbor one to four genes each for α- and β-tubulin isotypes. These may specify highly similar proteins, suggesting functional redundancy, or exhibit key differences, consistent with specialized roles. Some, but not all apicomplexans harbor genes for δ- and ε-tubulins, which are found in organisms that construct appendage-containing basal bodies. Critical roles for apicomplexan δ- and ε-tubulin are likely to be limited to microgametes, consistent with a restricted requirement for flagella in a single developmental stage. Sequence divergence or the loss of δ- and ε-tubulin genes in other apicomplexans appears to be associated with diminished requirements for centrioles, basal bodies, and axonemes. Finally, because spindle microtubules and flagellar structures have been proposed as targets for anti-parasitic therapies and transmission-blocking strategies, we discuss these ideas in the context of tubulin-based structures and tubulin superfamily properties.

Commensal Intestinal Protozoa-Underestimated Members of the Gut Microbial Community

The human gastrointestinal microbiota contains a diverse consortium of microbes, including bacteria, protozoa, viruses, and fungi. Through millennia of co-evolution, the host-microbiota interactions have shaped the immune system to both tolerate and maintain the symbiotic relationship with commensal microbiota, while exerting protective responses against invading pathogens. Microbiome research is dominated by studies describing the impact of prokaryotic bacteria on gut immunity with a limited understanding of their relationship with other integral microbiota constituents. However, converging evidence shows that eukaryotic organisms, such as commensal protozoa, can play an important role in modulating intestinal immune responses as well as influencing the overall health of the host. The presence of several protozoa species has recently been shown to be a common occurrence in healthy populations worldwide, suggesting that many of these are commensals rather than invading pathogens. This review aims to discuss the most recent, conflicting findings regarding the role of intestinal protozoa in gut homeostasis, interactions between intestinal protozoa and the bacterial microbiota, as well as potential immunological consequences of protozoa colonization.

Cystoisospora belli, liver disease and hypothesis on the life cycle

Cystoisospora belli causes chronic diarrhoea, acalculous cholecystitis, cholangiopathy and disseminated cystoisosporosis in patients with AIDS. Clinical manifestations and histological stages during C. belli infection in a patient with AIDS and liver disease were described. It was possible to identify sporozoite-like structures in the villus epithelium of the duodenum, close to the vascularization that underlies the basal membrane and unizoite tissue cysts near to the vascularization in the lamina propria. Unizoite tissue cysts were found inside of sinusoids in the liver communicating with the central vein and with a bile canaliculus and portal spaces. Based on these findings a hypothesis on C. belli life cycle could consider that the route of migration of unizoite tissue cysts up the liver is via the portal blood. The unizoite tissue cysts located in hepatic portal vein could migrated via sinusoid to central vein and general circulation through the venous system. The unizoite tissue cysts could also return via bile canaliculus to bile duct to portal triad. This hypothesis allows to understand the presence of unizoite stages in blood, the pathway by which the bile ducts become infected and unizoites in the liver being able to behave like hypnozoites that favour relapses and treatment failures.

Life Cycle and Transmission of Cyclospora cayetanensis: Knowns and Unknowns

Although infections with Cyclospora cayetanensis are prevalent worldwide, many aspects of this parasite’s life cycle and transmission remain unknown. Humans are the only known hosts of this parasite. Existing information on its endogenous development has been derived from histological examination of only a few biopsy specimens. Its asexual and sexual stages occur in biliary-intestinal epithelium. In histological sections, its stages are less than 10 μm, making definitive identification difficult. Asexual (schizonts) and sexual (gamonts) are located in epithelial cells. Male microgamonts have two flagella; female macrogametes contain wall-forming bodies. Oocysts are excreted in feces unsporulated. Sporulation occurs in the environment, but there are many unanswered questions concerning dissemination and survival of C. cayetanensis oocysts. Biologically and phylogenetically, C. cayetanensis closely resembles Eimeria spp. that parastize chickens; among them, E. acervulina most closely resembles C. cayetanensis in size. Here, we review known and unknown aspects of its life cycle and transmission and discuss the appropriateness of surrogates best capable of hastening progress in understanding its biology and developing mitigating strategies.

Intestinal apicomplexan parasitoses among a hospital-based population in Honduras, 2013-2019

Introduction:

Intestinal apicomplexa protozoa are a recognized cause of gastroenteritis. They are endemic in Honduras and their epidemiology varies in different population groups.

Objective:

To identify risk factors for cyclosporiasis, cryptosporidiosis, and cystoisosporiasis.

Materials and methods:

We conducted a case-control study in a hospital-based population. We performed the diagnosis using the modifed Ziehl-Neelsen staining technique and collected the information from laboratory records and clinical charts.

Results:

Cyclosporiasis was associated with diarrhea (OR=2.28; 95%CI: 1.10-4.89), weight loss (OR=12.7; 95%CI: 2.49-122.00), watery stools (OR=2.42; 95%CI: 1.26-4.65), and infection with another protozoan (OR=3.13; 95%CI: 1.66-5.95). Cryptosporidiosis was associated with HIV infection (OR=15.43; 95%CI: 3.34-71.22), diarrhea (OR=3.52; 95%CI: 1.40-9.40), lymphopenia (OR=6.16; 95%CI: 1.99-18.98), and green color stools (OR=3.00; 95%CI: 1.23-7.30). Cystoisosporiasis was associated with HIV infection (OR=11.20; 95%CI: 3.53-35.44), diarrhea (OR=7.30; 95%CI: 1.89-28.52), leukopenia (OR=4.28; 95%CI: 1.33-13.75), green color stools (OR=11.59; 95%CI: 1.16-558.60), and Charcot-Leyden crystals (OR=11.59; 95%CI: 1.16-558.60).

Conclusions:

In this hospital-based population from Honduras, HIV infection was a risk factor for cryptosporidiosis and cystoisosporiasis, but not for cyclosporiasis.

Identification of two potential aetiological agents of chronic diarrhoea in an immunocompromised patient in Cuba using conventional and molecular diagnostic techniques

The aetiology of diarrhoea in a patient in Cuba with HIV was investigated. Although molecular diagnostics are still not used in many under-resourced settings, here traditional methods were supported by use of PCR. This approach enabled detection of a dual infection (Cystoisospora belli and Enterocytozoon bieneusi), the latter of which was not identified by microscopy with Didier's trichromic staining.

An annotated checklist of the eukaryotic parasites of humans, exclusive of fungi and algae

The classification of "parasites" in the medical field is a challenging notion, a group which historically has included all eukaryotes exclusive of fungi that invade and derive resources from the human host. Since antiquity, humans have been identifying and documenting parasitic infections, and this collective catalog of parasitic agents has expanded considerably with technology. As our understanding of species boundaries and the use of molecular tools has evolved, so has our concept of the taxonomy of human parasites. Consequently, new species have been recognized while others have been relegated to synonyms. On the other hand, the decline of expertise in classical parasitology and limited curricula have led to a loss of awareness of many rarely encountered species. Here, we provide a comprehensive checklist of all reported eukaryotic organisms (excluding fungi and allied taxa) parasitizing humans resulting in 274 genus-group taxa and 848 species-group taxa. For each species, or genus where indicated, a concise summary of geographic distribution, natural hosts, route of transmission and site within human host, and vectored pathogens are presented. Ubiquitous, human-adapted species as well as very rare, incidental zoonotic organisms are discussed in this annotated checklist. We also provide a list of 79 excluded genera and species that have been previously reported as human parasites but are not believed to be true human parasites or represent misidentifications or taxonomic changes.

Investigation of neglected protists Blastocystis sp. and Dientamoeba fragilis in immunocompetent and immunodeficient diarrheal patients using both conventional and molecular methods

Introduction

The clinical significance of Blastocystis sp. and Dientamoeba fragilis in patients with gastrointestinal symptoms is a controversial issue. Since the pathogenicity of these protists has not been fully elucidated, testing for these organisms is not routinely pursued by most laboratories and clinicians. Thus, the prevalence of these organisms and the subtypes of Blastocystis sp. in human patients in Turkey are not well characterized. This study aimed to determine the prevalence of Blastocystis sp. and D. fragilis in the diarrheic stool samples of immunodeficient and immunocompetent patients using conventional and molecular methods and to identify Blastocystis sp. subtypes using next generation sequencing.

Material and methods

Individual stool specimens were collected from 245 immunodeficient and 193 immunocompetent diarrheic patients between March 2017 and December 2019 at the Gazi University Training and Research Hospital in Ankara, Turkey. Samples were screened for Blastocystis sp. and D. fragilis by conventional and molecular methods. Molecular detection of both protists was achieved by separate qPCRs targeting a partial fragment of the SSU rRNA gene. Next generation sequencing was used to identify Blastocystis sp. subtypes.

Results

The prevalence of Blastocystis sp. and D. fragilis was 16.7% and 11.9%, respectively as measured by qPCR. The prevalence of Blastocystis sp. and D. fragilis was lower in immunodeficient patients (12.7% and 10.6%, respectively) compared to immunocompetent patients (21.8% and 13.5%, respectively). Five Blastocystis sp. subtypes were identified and the following subtype distribution was observed: ST3 54.4% (n = 37), ST2 16.2% (n = 11), ST1 4.4% (n = 3), ST6 2.9% (n = 2), ST4 1.5% (n = 1), ST2/ST3 11.8% (n = 8) and ST1/ST3 8.8% (n = 6). There was no statistically significant difference in the distribution of Blastocystis sp. subtypes between immunocompetent and immunodeficient patients.

Conclusion and recommendation

Our findings demonstrated that Blastocystis sp. and D. fragilis are commonly present in immunocompetent and immunodeficient patients with diarrhea. This study is the first to use next generation sequencing to address the presence of Blastocystis sp. mixed subtypes and intra-subtype variability in clinical samples in Turkey.

Blastocystis sp. and Dientamoeba fragilis are single-cell parasites of the human intestine which are common worldwide and reported in cases with gastrointestinal symptoms. However, the role of Blastocystis sp. and D. fragilis in patients with gastrointestinal symptoms is still controversial because their presence is not always associated with symptoms. As some intestinal parasitic infections can cause severe illness in immunocompromised individuals careful consideration of intestinal protist infection is warranted. However, testing for Blastocystis sp. and D. fragilis is not routinely carried out by most laboratories and clinicians. Therefore, this study aimed to determine the prevalence of Blastocystis sp. and D. fragilis in immunocompetent and immunosuppressed patients with diarrhea by conventional and molecular methods. Both Blastocystis sp. and D. fragilis were detected more frequently by quantitative polymerase chain reaction than by conventional methods. Next generation sequencing was used to characterize the diversity and frequency of Blastocystis sp. subtypes and mixed subtypes in patients in Turkey. Five Blastocystis sp. subtypes (ST1, ST2, ST3, ST4 and ST6) were detected. ST3 was the most frequent subtype in both immunocompetent and immunosuppressed patients. Mono-infections were more common than mixed subtype infections. Our findings showed that Blastocystis sp. and D. fragilis are commonly present in immunocompetent and immunodeficient patients with diarrhea.

Molecular detection of Cystoisospora belli by single-run polymerase chain reaction in stool samples

INTRODUCTION

Cystoisospora belli (C. belli) is the only pathogenic species of the Cystoisospora genus responsible for severe diarrhea in immunocompromised patients. Most common microscopic method of diagnosis is less sensitive due to intermittent shedding of oocysts. We developed a new single-run polymerase chain reaction (PCR)-based diagnostic assay for C. belli.

METHODS

A new single-run PCR-based diagnostic assay was standardized for the detection of C. belli. Diagnostic reproducibility and repeatability of the PCR assay were evaluated. A cross-sectional analytical study was done on a total of 354 stool samples collected from 331 immunocompromised patients with diarrhea. All the stool samples were tested for the presence of oocysts of C. belli and were also tested by our new PCR assay for C. belli. Three of the representative PCR products were confirmed by sequencing. Fisher's exact test was used to compare the two proportions.

RESULTS

Microscopy detected C. belli in 11/354 (3.1%) of stool samples, and the new PCR-based assay detected C. belli in 16/354 (4.5%). The new single-run PCR-based assay detected C. belli in all the stool samples which were tested positive by microscopy and additionally detected C. belli in five stool samples. The developed PCR assay detected statistically significant proportion of C. belli (p < 0.001) as compared to microscopy. The 795 base pair PCR product from one microscopy positive stool sample and two microscopy negative stool samples were confirmed by sequencing.

CONCLUSION

Our newly developed single-run PCR-based detection assay for C. belli is robust and reproducible. It may be used for molecular diagnosis of cystoisosporiasis especially in transplant, pediatrics, and human immunodeficiency virus (HIV) positive patients.

Comparison of Two Real-Time PCR Assays Targeting Ribosomal Sequences for the Identification of Cystoisospora belli in Human Stool Samples

Cystoisospora (C.) belli is a coccidian parasite associated with acute or chronic gastroenteritis in immunocompromised patients. Dissatisfactory sensitivity of microscopy as the diagnostic standard approach has been described. Here, we comparatively evaluated two real-time PCRs targeting ribosomal RNA gene sequences of C. belli in stool in a test comparison without a reference standard applying latent class analysis. Therefore, 1000 stool samples from Ghanaian HIV (human immunodeficiency virus) patients (n = 905) as well as military returnees from the tropics (n = 95) were assessed by both assays in parallel. After the exclusion of 33 samples showing PCR inhibition, 29 and 33 positive results were recorded with the 5.8S rRNA gene/ITS-2 sequence PCR and the ITS-2 sequence PCR, respectively, resulting in an accuracy-adjusted prevalence of 3.2%. Nearly perfect agreement between both assays was indicated by Fleiss’ kappa of 0.933 with sensitivity and specificity of 92.8% and 100% as well as 100% and 99.8% for the 5.8S rRNA gene/ITS-2 sequence PCR and the ITS-2 sequence PCR, respectively. Both assays proved to be suitable for the diagnosis of C. belli in human stool samples with slightly better sensitivity of the ITS-2 sequence assay, while the 5.8S rRNA gene/ITS-2 sequence PCR may be considered for confirmatory testing.

Detection of enteroparasites in foliar vegetables commercialized in street- and supermarkets in Aparecida de Goiânia, Goiás, Brazil

Foliar vegetables contaminated with fecal residues are an important route of transmission of intestinal parasites to humans. The aim of this study was to evaluate the presence of parasitic forms of protozoa and helminths on lettuces (Lactuca sativa) and collard greens (Brassica oleracea) sold in street- and supermarkets in the city of Aparecida de Goiânia, Goiás, Brazil. A total of 30 samples of each vegetable (15 samples from each supermarkets and street markets) was analyzed. All samples were processed by spontaneous sedimentation method and centrifugal flotation. In 45% of the samples, immature forms of intestinal parasites were identified with 66.7% helminths eggs and 33.3% protozoan cysts or oocysts. Significantly more lettuce samples were contaminated with eggs, cysts or oocyst of at least one parasite than collard green samples (U=216; Z=-3.45; P <0.001). The parasitic forms were identified morphologically up to the family level with eggs of Ancylostomatidae, Strongyloididae, Ascarididae and Taeniidae, or oocysts of Eimeriidae, to the genus with Cystoisospora sp. and Toxocara sp., and to the species level with Cystoisospora canis, Dipylidium caninum and Hymenolepis nana. The presence of these infective agents in lettuce and collard green from both street- and supermarkets highlights the high risk of spreading parasites by eating raw vegetables sold in Aparecida de Goiânia.

Chronic Cystoisospora belli infection in a Colombian patient living with HIV and poor adherence to highly active antiretroviral therapy

Cystoisospora belli is an intestinal Apicomplexan parasite associated with diarrheal illness and disseminated infections in humans, mainly immunocompromised individuals such as those living with the human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS). An irregular administration of highly active antiretroviral therapy (HAART) in HIV patients may increase the risk of opportunistic infections like cystoisosporiasis. We describe here a case of C. belli infection in a Colombian HIV patient with chronic gastrointestinal syndrome and poor adherence to HAART. His clinical and parasitological cure was achieved with trimethoprim-sulfamethoxazole treatment. Although a reduction in the number of C. belli cases has been observed since the use of HAART, this parasite still has to be considered as a differential diagnosis of diarrheal disease in HIV/AIDS patients. Effective interventions enhancing adherence to HAART should be included in HIV patient care programs.

Chronic cystoisosporiasis in an immunocompetent adult: A case report

RATIONALE

Cystoisosporiasis is an intestinal infectious disease caused by a coccidian protozoa, Cystoisospora belli (C. belli). It can cause prolonged and refractory diarrhea most commonly in immunocompromised patients, while immunocompetent individuals usually exhibit no symptoms or self-limited diarrhea.

PATIENT CONCERNS

We herein report a case of chronic cystoisosporiasis in an immunocompetent patient. A 62-year-old man, who had been first diagnosed with cystoisosporiasis 15 years ago and had been treated with oral administration of trimethoprim-sulfamethoxazole (TMP-SMX), complained of persistent watery diarrhea. He was negative for anti-human immunodeficiency virus antibody and anti-human T-cell leukemia virus type 1 (HTLV-1) antibody.

DIAGNOSIS

Biopsy specimens from the duodenum revealed oocysts in the atrophic absorptive epithelium and protozoa were detected through stool examination, indicating the recurrence of cystoisosporiasis. Capsule endoscopy showed diffuse atrophic mucosa with white villi in the entire small intestine. We diagnosed him with chronic cystoisosporiasis that occurred in an immunocompetent adult.

INTERVENTIONS

Since oral administration of TMP-SMX and ciprofloxacin were ineffective, the intravenous administration of TMP-SMX was initiated.

OUTCOMES

Intravenous TMP-SMX exhibited a significant improvement.

LESSONS

This case indicates that even immunocompetent individuals may develop recurrent and refractory cystoisosporiasis. Furthermore, intravenous treatment of antibiotic agents should be considered when the impaired absorptive ability from the small intestine is suspected.

Cystoisospora belli associated persistent diarrhea in an AIDS patient

Cystoisospora belli infection is regarded as an indicator disease of AIDS in Japan; however, only a few case reports showing this association are present. Our case study involved a 49-year-old Thai woman living in Japan since her marriage to a Japanese man. She was repeatedly hospitalized owing to persistent diarrhea. Considering her native country, she was suggested of having AIDS. Serological examination for HIV-1 tested positive, and C. belli infection was diagnosed on detection of oocysts in her stool samples. She was treated successfully for the parasitic infection with oral trimethoprim-sulphamethoxazole therapy for 10 days. No AIDS-associated opportunistic infections other than cystoisosporiasis were detected. Thus, this study suggests that an immunocompromised individual with persistent and recurrent diarrhea should be examined to confirm for C. belli infection. Moreover, it is possible that a person in a high-latitude region will develop a parasitic infection common in tropical areas because of globalization.

Pitfalls in Morphologic Diagnosis of Pathogens: Lessons Learned From the Pseudo-Cystoisospora Epidemic

Multiple groups have recently reported involvement of the gallbladder mucosa of immunocompetent patients by cystoisospora organisms. However, this has recently been disproved with the support of molecular and ultrastructural studies. Here we present a summary of these events, recounting how this pseudo-Cystoisospora epidemic began and ended. This review also highlights the important role played by ancillary techniques in supplementing the morphologic diagnosis of pathogens.

Endogenous Developmental Cycle of the Human Coccidian Cyclospora cayetanensis

Cyclospora cayetanensis is a coccidian parasite of humans of known and growing importance. However, we are surprisingly naïve as to our understanding of how to diagnose it and how it develops inside the human body. Here we provide details of the developmental stages of C. cayetanensis in the gallbladder of a 33-yr-old male with human immunodeficiency virus. The gallbladder was removed surgically in 2001 because of severe abdominal pain. For the present study, the archived paraffin block of gallbladder was processed for light microscopy and transmission electron microscopy (TEM). Histological sections were examined after staining with hematoxylin and eosin (HE) or using the periodic acid Schiff (PAS) reaction. Immature and mature asexual stages, gamonts, and oocysts were seen in epithelial cells, both in the superficial epithelium and in glands. The merozoites were present singly, in pairs, and 3 or more in a single parasitophorous vacuole in the host cytoplasm. Up to 6 nuclei were seen in immature schizonts without evidence of merozoite formation. Mature schizonts were 7.6 × 5.1 μm and contained up to 10, 3-4 μm long merozoites. Merozoites were 0.6 to 2.0 μm wide, and their shape varied from pear-shaped to slender. Merozoites were generally PAS-positive; however, some were intensely positive, some had only minute granules, while others were PAS-negative. The microgamonts (male) were 6.6 × 5.2 μm and contained fewer than 20 microgametes around a residual body. The microgametes were up to 2 μm long and were flagellated. Macrogamonts (female) contained distinctive eosinophilic wall-forming bodies that varied in size and were less than 1 μm in HE-stained sections. Macrogamonts were 5.8-6.5 × 5.3-6.5 μm. Oocysts in sections were unsporulated and had a diameter of 5.7-7.5 μm. The TEM examination confirmed the histologic findings. The DNA extracted from paraffin sections was confirmed as C. cayetanensis with real-time PCR. The detailed description of the life cycle stages of C. cayetanensis reported here in an immunosuppressed patient could facilitate histopathologic diagnosis of this parasite. We have shown that the parasite's development more closely resembles that of Cystoisospora than Eimeria and that the parasite has multiple nuclei per immature meront indicating schizogony, and we have undermined evidence for a Type II meront.