Study of the pathogenic potential of Dientamoeba fragilis in experimentally infected mice

Observations on the transmission of Dientamoeba fragilis and the cyst life cycle stage

Little is known about the life cycle and mode of transmission of Dientamoeba fragilis. Recently it was suggested that fecal–oral transmission of cysts may play a role in the transmission of D. fragilis. In order to establish an infection, D. fragilis is required to remain viable when exposed to the pH of the stomach. In this study, we investigated the ability of cultured trophozoites to withstand the extremes of pH. We provide evidence that trophozoites of D. fragilis are vulnerable to highly acidic conditions. We also investigated further the ultrastructure of D. fragilis cysts obtained from mice and rats by transmission electron microscopy. These studies of cysts showed a clear cyst wall surrounding an encysted parasite. The cyst wall was double layered with an outer fibrillar layer and an inner layer enclosing the parasite. Hydrogenosomes, endoplasmic reticulum and nuclei were present in the cysts. Pelta-axostyle structures, costa and axonemes were identifiable and internal flagellar axonemes were present. This study therefore provides additional novel details and knowledge of the ultrastructure of the cyst stage of D. fragilis.

Dientamoeba fragilis associated with microbiome diversity changes in acute gastroenteritis patients

This study examined the correlation between intestinal protozoans and the bacterial microbiome in faecal samples collected from 463 patients in New Zealand who were diagnosed with gastroenteritis. In comparison to traditional microscopic diagnosis methods, Multiplexed-tandem PCR proved to be more effective in detecting intestinal parasites. Among the identified protozoans, Blastocystis sp. and Dientamoeba fragilis were the most prevalent. Notably, D. fragilis was significantly associated with an increase in the alpha-diversity of host prokaryotic microbes. Although the exact role of Blastocystis sp. and D. fragilis as the primary cause of gastroenteritis remains debatable, our data indicates a substantial correlation between these protozoans and the prokaryote microbiome of their hosts, particularly when compared to other protists or patients with gastroenteritis but no detectable parasitic cause. These findings underscore the significance of comprehending the contributions of intestinal protozoans, specifically D. fragilis, to the development of gastroenteritis and their potential implications for disease management.

A Cross-Sectional Study on the Occurrence of the Intestinal Protist, Dientamoeba fragilis, in the Gut-Healthy Volunteers and Their Animals

Dientamoeba fragilis is a cosmopolitan intestinal protist colonizing the human gut with varying prevalence depending on the cohort studied and the diagnostic methods used. Its role in human health remains unclear mainly due to the very sporadic number of cross-sectional studies in gut-healthy populations. The main objective of this study was to expand knowledge of the epidemiology of D. fragilis in gut-healthy humans and their animals. A total of 296 stool samples from humans and 135 samples from 18 animal species were analyzed. Using qPCR, a prevalence of 24% was found in humans in contrast to conventional PCR (7%). In humans, several factors were found to influence the prevalence of D. fragilis. A more frequent occurrence of D. fragilis was associated with living in a village, traveling outside Europe and contact with farm animals. In addition, co-infection with Blastocystis spp. was observed in nearly half of the colonized humans. In animals, D. fragilis was detected in 13% of samples from eight species using qPCR. Our molecular phylogenies demonstrate a more frequent occurrence of Genotype 1 in gut-healthy humans and also revealed a likely a new protist species/lineage in rabbits related to D. fragilis and other related organisms.

Gut Non-Bacterial Microbiota: Emerging Link to Irritable Bowel Syndrome

As a common functional gastrointestinal disorder, irritable bowel syndrome (IBS) significantly affects personal health and imposes a substantial economic burden on society, but the current understanding of its occurrence and treatment is still inadequate. Emerging evidence suggests that IBS is associated with gut microbial dysbiosis, but most studies focus on the bacteria and neglect other communities of the microbiota, including fungi, viruses, archaea, and other parasitic microorganisms. This review summarizes the latest findings that link the nonbacterial microbiota with IBS. IBS patients show less fungal and viral diversity but some alterations in mycobiome, virome, and archaeome, such as an increased abundance of Candida albicans. Moreover, fungi and methanogens can aid in diagnosis. Fungi are related to distinct IBS symptoms and induce immune responses, intestinal barrier disruption, and visceral hypersensitivity via specific receptors, cells, and metabolites. Novel therapeutic methods for IBS include fungicides, inhibitors targeting fungal pathogenic pathways, probiotic fungi, prebiotics, and fecal microbiota transplantation. Additionally, viruses, methanogens, and parasitic microorganisms are also involved in the pathophysiology and treatment. Therefore, the gut nonbacterial microbiota is involved in the pathogenesis of IBS, which provides a novel perspective on the noninvasive diagnosis and precise treatment of this disease.

Investigation of Dientamoeba fragilis and Blastocystis in patients from Turkey with ulcerative colitis and irritable bowel syndrome: Any relation with genotypes?

Blastocystis sp. and Dientamoeba fragilis are two most common protists worldwide, whose pathogenic potentials are a matter of debate since their discovery. This study aims to investigate the relationship between the activation of ulcerative colitis (UC) and irritable bowel syndrome (IBS) with these protists. A total of 100 patients (35 IBS, 35 active UC, and 30 remittent UC), diagnosed at Hacettepe University Adult Hospital (Ankara, Turkey), were screened for D. fragilis and Blastocystis sp. with microscopic examination using the methods of wet mount, trichrome staining, conventional PCR, nested PCR, real-time PCR and genotyping. Eight patients (4 IBS, 2 active, and 2 remittent UC patients) were found to be D. fragilis positive. 18S rRNA region of the parasite was amplified in four of the patients, whereas cathepsin L-like cysteine peptidase; clan Sc, family S9, serine peptidase; and clan MH, family M20 metallopeptidase in six different patients. All isolates were Genotype 1. Sequence results showed very limited diversity. A total of nine patients (3 IBS, 5 active UC, 1 remittent UC) were found to be positive for Blastocystis sp., all of which were Subtype 3. One active UC and one IBS patient were found to be positive for both parasites. No statistically significant difference was detected between the patient groups in means of parasite detection. D. fragilis was found to be related to older age (p=0,045). In our study, no significant correlation was identified between D. fragilis and Blastocystis sp., and the activation of UC and IBS. More studies are needed on the host-parasite relationship, including the role of gut microbiota, together with transcriptomic and metabolomic assessments to unveil the pathogenicity of both protists.

Diagnostic and Therapeutic Considerations Towards Dientamoeba fragilis in Children: A Survey Amongst General Practitioners and Pediatricians in the Netherlands

ABSTRACT

This survey was undertaken to obtain insight in the attitude of Dutch physicians towards pathogenicity, diagnostic- and therapeutic approach towards Dientamoeba fragilis in children. Physicians were invited by e-mail for a questionnaire. A total of 211 of 450 physicians (46.9%) completed the questionnaire, including 67 general practitioners (GPs) and 144 pediatricians. Of all respondents, 175 of 211 (82.9%) considered D fragilis a "potential pathogen", when other causes of gastro-intestinal complaints are ruled out. Only 16 of 211 (7.6%) performed diagnostic tests regularly. Diagnostic tests were performed by 162 of 211 (77%) of respondents in children with diarrhea and abdominal pain in consideration of duration of symptoms. Fecal polymerase chain reaction (PCR) was diagnostic modality of preference. Eighty-nine of 142 (62.7%) prescribed metronidazole as antibiotic of first choice. This study shows heterogeneity in clinical practice amongst Dutch physicians regarding diagnostic- and therapeutic approach of D fragilis in children. Different attitude towards pathogenicity and inconsistent guidelines could be causative factors.

Dientamoeba fragilis in children: a systematic review on diagnostic considerations and efficacy of treatment

Introduction: The presence of D. fragilis in feces is characterized by an asymptomatic carrier ship to a spectrum of gastrointestinal symptoms. However, a causal relationship remains to be elucidated. In this systematic review, we aimed to evaluate the relationship between the eradication of D. fragilis and symptoms to establish the strength of evidence that D. fragilis in symptomatic children warrants antibiotic treatment.Areas covered: This systematic review covers a challenge in daily clinical practice. Is it necessary to test for D. fragilis in children with gastrointestinal symptoms and does a positive fecal PCR test warrant treatment?Expert opinion: Testing for D. fragilis seems justified in a selection of children with persistent unexplained chronic abdominal pain and diarrhea. Treatment of D. fragilis should be withhold until other causes like celiac disease have been excluded. Both microscopic and Real Time-PCR methods (or a combination of the two) can be used for diagnosis. Paromomycin or clioquinol are antibiotics of choice based on their small spectrum of activity, fewer side effects, and better eradication rates than metronidazole. Future randomized studies, with strict inclusion criteria, appropriate diagnostic testing, and doses of antibiotics based on bodyweight are warranted.

Fecal calprotectin as a factor that supports the pathogenicity of Dientamoeba fragilis

Calprotectin is a protein that is mostly released from neutrophils, monocytes, macrophages and submucosal epithelial cells. Fecal calprotectin (f-CP) is a marker of intestinal inflammation. There are some discussions about the pathogenicity of D. fragilis in the gastrointestinal tract. In this study, we investigated whether f-CP level is a factor supporting the pathogenicity of D. fragilis. The f-CP levels were evaluated in patients with only D. fragilis positive in comparison with healthy controls. Moreover, the levels of f-CP were investigated in fecal samples of D. fragilis negative patients with gastrointestinal complaints. The fecal samples were collected from three groups. Three groups of fecal samples were examined directly microscopy, trichrome staining, cultivation, enzyme immunoassay (EIA) and real-time PCR assay. In the first group (Group 1, n = 34), patient stool samples with gastrointestinal symptoms (without other pathogens) found only with D. fragilis were included. In the second group (Group 2, n = 31), there were patients' stool samples with gastrointestinal symptoms that D. fragilis was negative (but there may be other pathogenic agents). In the control group (Group 3, n = 23), we used fecal samples collected from healthy volunteers without any infection or gastrointestinal complaints. The collected fecal samples were stored at -20 °C until analysis. Levels of f-CP were determined by using human calprotectin ELISA kits. Total of 88 patients were enrolled in three different groups. We obtained f-CP levels as follows: 33.40 ng/mg protein in the group 1, 15.99 ng/mg protein in the group 2 and 1.54 ng/mg protein in the group 3. Statistically significant difference in f-CP levels of the group 1 and the group 2 were obtained when compared with healthy controls (p < 0.0001). However, the f-CP levels of the group 1 were not significantly different from the group 2 (p > 0.99). In conclusion, increased levels of f-CP are shown as a marker of an inflammatory disease of the lower gastrointestinal tract in infected humans. There is continues controversy about the pathogenicity of D. fragilis in symptomatic and asymptomatic patients. The findings of this study contribute to the ongoing debate about the pathogenicity of D. fragilis. In our study, the potential pathogenicity of D. fragilis is associated with increased f-CP concentrations with parasite detection in the fecal samples and therefore we assume that the parasite is not only a harmless commensal. In summary, higher levels of f-CP found in D. fragilis positive patients suggest the importance of researches that support the pathogenicity of indicated parasite.

No association between abdominal pain and Dientamoeba in Dutch and Belgian children

OBJECTIVE

To study the association between Dientamoebafragilis colonisation and faecal calprotectin to see whether the parasite is a harmless commensal or a gut pathogen.

DESIGN

Cross-sectional study of previously collected stool samples.

SETTING AND PATIENTS

Two hundred stool samples originated from children aged 5-19 years with chronic abdominal pain and diarrhoea, who were seen in paediatric clinics in the Netherlands and Belgium and in whom somatic gastrointestinal disorders were excluded. Another 122 samples came from a healthy community-based reference population of the same age. All stool samples were analysed with real-time PCR for the detection of D. fragilis and with an ELISA for calprotectin-a biomarker of gastrointestinal inflammation.

MAIN OUTCOME MEASURES

Prevalence of D. fragilis colonisation and results of stool calprotectin testing.

RESULTS

D. fragilis was detected in 45% (95% CI 38% to 51%) of patients and in 71% (95% CI 63% to 79%) of healthy children. Median (IQR) concentrations of calprotectin in patients and healthy children with a positive PCR result were not different from those with a negative PCR result (40 (40-55) μg/g vs 40 (40-75) μg/g, respectively).

CONCLUSION

Since D. fragilis colonisation is most prevalent in healthy children and is not associated with an increase in faecal calprotectin concentration, our data do not support the inference that D. fragilis is a pathogenic parasite. Routinely testing for D. fragilis in children with chronic abdominal pain should therefore be discouraged.

The possible role of bacteria, viruses, and parasites in initiation and exacerbation of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a prolonged and disabling functional gastrointestinal disorder with the incidence rate of 18% in the world. IBS could seriously affect lifetime of patients and cause high economic burden on the community. The pathophysiology of the IBS is hardly understood, whereas several possible mechanisms, such as visceral hypersensitivity, irregular gut motility, abnormal brain-gut relations, and the role of infectious agents, are implicated in initiation and development of this syndrome. Different studies demonstrated an alteration in B-lymphocytes, mast cells (MC), T-lymphocytes, and cytokine concentrations in intestinal mucosa or systemic circulation that are likely to contribute to the formation of the IBS. Therefore, IBS could be developed in those with genetic predisposition. Infections' role in initiation and exacerbation of IBS has been investigated by quite several clinical studies; moreover, the possible role of some pathogens in development and exacerbation of this disease has been described. It appears that the main obligatory pathogens correspond with the IBS disease, Clostridium difficile, Escherichia coli, Mycobacterium avium subspecies paratuberculosis, Campylobacter concisus, Campylobacter jejuni, Chlamydia trachomatis, Helicobacter pylori, Pseudomonas aeruginosa, Salmonella spp, Shigella spp, and viruses, particularly noroviruses. A number of pathogenic parasites (Blastocystis, Dientamoeba fragilis, and Giardia lamblia) may also be involved in the progression and exacerbation of the disease. Based on the current knowledge, the current study concludes that the most common bacterial, viral, and parasitic pathogens may be involved in the development and progression of IBS.

Can Giardia Infection Impair the Diagnostic Level of Fecal Calprotectin in Patients with Inflammatory Bowel Disease? A Case Report

Inflammatory bowel disease (IBD) is attributed to complex conditions of gastrointestinal tract that is frequently reported all over the world. Fecal calprotectin evaluation is described as a primary tool to screen IBD patients. There are reports showing the confounding role of some microbial agents in diagnostic levels of calprotectin. A 32-yr-old woman with symptoms like IBD/IBS (irritable bowel syndrome); admitted to IBD Clinic of Behbood Research Center for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran, Jan 2017 for evaluation of the level of fecal calprotectin. In spite of high level of calprotectin, trophozoite of Giardia intestinalis was observed in direct examination of stool sample. Microbial pathogens can lead to false elevation of fecal calprotectin and misdiagnosis of gastrointestinal patients suspected to IBD.