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Purpose: Dientamoeba fragilis (D. fragilis) is a common intestinal protozoan with a global distribution. In the present study, we aimed to determine genetic diversity of D. fragilis isolates with multilocus sequence typing (MLST) in the southwest of Turkey and analyse the clinical findings., Materials and Methods: The study included faecal samples from 200 individuals in Aydin, Turkey. The positivity of D. fragilis was determined with 18 S rRNA gene-based PCR assay. Six nested-PCR reactions were set to amplify partial D. fragilis housekeeping genes in the positive samples. The sequences were aligned with the references from GenBank to detect nucleotide polymorphisms and haplotypes. Additionally, the clinical findings and demographic characteristics of patients were statistically analysed between D. fragilis-infected and non-infected cases., Results: The positivity of D. fragilis was 16% (32 out of 200 cases) with 18 S rRNA based-PCR, and all were classified as "genotype 1". The analysis of six MLST loci revealed different haplotypes only at one locus; the remaining five loci exhibited no polymorphisms. The haplotypes in the present study were identical to at least one previously reported reference, except the locus "large subunit of RNA polymerase II" locus. There were no significant differences in any of the clinical findings or demographic characteristics between the infected and non-infected groups., Conclusions: Our study revealed a low genetic diversity of D. fragilis isolates from Turkey, like other countries including Italy, Denmark, the UK, Australia, and Brazil. The high degree of sequence similarity in housekeeping genes indicated the clonal distribution of D. fragilis., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Blastocystis sp. and Dientamoeba fragilis are intestinal protists, which are common worldwide, but the pathogenic role of these organisms in gastrointestinal diseases is still controversial. This study aimed to investigate the frequency of Blastocystis sp. and D. fragilis in stool samples from adult patients with celiac disease (CD) by using conventional and molecular methods. A total of 75 patients with CD and 75 healthy individuals were included in this study. Fresh stool specimens collected from each individual were analyzed by conventional and molecular methods. The overall prevalence of Blastocystis sp. and D. fragilis was 41.3% (31/75) and 24% (18/75) in patients with CD, and 46.7% (35/75) and 13.3% (10/75) in healthy controls, respectively. There was no statistically significant difference in the prevalence of Blastocystis sp. and D. fragilis between CD patients and healthy individuals. Blastocystis sp. subtypes were identified in 20 CD and 16 control patients and the overall subtype distribution was observed as ST1 13.9%, ST2 30.6%, and ST3 55.6%. The prevalence of Blastocystis sp. and D. fragilis in adults with CD is similar to the prevalence of protozoa in healthy adults. In this study, the most prevalent Blastocystis subtype was ST3 and the most frequent allele was a34 in both CD patients and healthy individuals. No significant difference was found between the two groups in terms of the detection rates of Blastocystis sp. and D. fragilis, and it is thought that both protists may be colonisers of the intestinal microbiome., Competing Interests: Declaration of competing interest Not applicable., (Copyright © 2024. Published by Elsevier B.V.)

Dientamoeba fragilis (D. fragilis) represents a common protozoan in both high and low income countries. Despite this, epidemiological data on dientamoebiasis are still limited, and it is possible that the actual prevalence rates of D. fragilis have been underestimated due to the challenges in its detection and identification. In the present study, symptomatic patients from Rome (Central Italy) were surveyed for two years to determine D. fragilis percentage of infection and genotypes. Stool samples collection was performed over 864 patients, DNA extracted, and RT-PCR performed by the SeeGene Allplex™ Gastrointestinal Parasite Panel Assays. Seventy-nine resulted positive for D. fragilis (9.1%). Co-infections were detected in 22 isolates: 21 displayed Blastocystis sp. + D. fragilis (27.8%). Based on the sequence of a central fragment of the SSU rRNA gene, only genotype 1 was identified. These findings are among the few available data regarding genetic diversity of D. fragilis in Italy. Large-scale human and animal research are required to enhance our knowledge of prevalence, host range, genetic variability and zoonotic transmission of this little-known intestinal protozoan., Competing Interests: Declaration of Competing Interest The authors declare that no conflict of interest exists., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Dientamoeba fragilis is a ubiquitous intestinal parasite with detection in the stools that has become increasingly frequent following the advent of PCR as a routine screening tool. However, the pathogenicity of this parasite is still much debated. In order to assess the potentially pathogenic nature of this protozoan, a retrospective case-control study was carried out between January and December 2020 on patients from Toulouse University Hospital, with the aim of evaluating the potential clinical effects and changes in laboratory parameters linked to the presence and load of D. fragilis in stools. After matching age, sex and mode of care (consultation or hospitalisation), no significant difference was observed in the frequency of clinical signs between the 36 patients who tested positive for Dientamoeba fragilis PCR in their stools and the 72 control patients who were PCR negative for this protozoan. The presence of D. fragilis in the faeces was not associated with changes in laboratory parameters. Furthermore, a high digestive load of D. fragilis had no identifiable impact on clinical and laboratory parameters. Only the concomitant presence of Blastocystis sp. in stools was significantly more frequent in the D. fragilis group (uni- and multivariate analysis). Finally, this study showed no significant difference in clinical or laboratory signs between patients carrying Dientamoeba fragilis and the control group, regardless of the intestinal parasite load, suggesting that D. fragilis could be considered a commensal of the digestive tract., (© G. Tchamwa Bamini et al., published by EDP Sciences, 2024.)

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.

Dientamoeba fragilis is a flagellated protozoan with amoeba-like morphology that inhabits the human gastrointestinal tract. It is endemic in a vast geography around the world, including developed countries. There are limited studies on non-human hosts of the parasite, and suitable hosts have not been clarified. The parasite has been detected in non-human primates, pigs, cats, dogs and rats. There is no study in the literature investigating and detecting the presence of this parasite in cattle. In this study, stool samples taken from 163 different cattle and calves from 11 different farms between March 2017 and May 2022 were examined for the detection of D. fragilis via PCR. Trichrome staining was performed on all PCR-positive samples. The isolates with the expected amplicon size were sequenced using the 18S ribosomal RNA region, and their genotypes were determined by BLAST analysis. Sequences were analysed with the most similar and reference sequences in the literature, forming a phylogenetic tree. We detected D. fragilis in 31 (19.01%) of the 163 stool samples. D. fragilis cysts/trophozoites were detected by trichrome staining method in six of 31 samples. All PCR products selected for molecular analysis from positive samples had the same nucleotide sequence. As a result of BLAST analysis, all sequences were determined to belong to D. fragilis genotype 1. This study determined for the first time that cattle are suitable hosts for D. fragilis. Furthermore, the parasite subtype we detected belongs to genotype 1, which is the most common type in humans, suggesting that the parasite may have a zoonotic character. Our result is important in terms of the epidemiology of the parasite, as the mode of transmission is controversial, and available data on its suitable hosts are limited., (© 2022 Wiley-VCH GmbH.)

The protozoan Dientamoeba fragilis is one of the most common parasites in the digestive system of humans worldwide. The host range and transmission routes of D. fragilis, including the role of animals, are still ambiguous with few reports from non-human primates, sheep, rodents, pigs, a cat and a dog. In this study, we used microscopic and TaqMan qPCR analyses to investigate D. fragilisin 150 faecal samples from pet budgerigars (Melopsittacus undulatus) in the Central Anatolia Region of Turkey. Dientamoeba fragilis DNA was detected in 32 samples, resulting in a mean prevalence of 21.3%. In microscopic examination, trophozoites/cysts of D. fragilis were detected in 13 of 32 qPCR-positive samples. SSU rRNA sequence analyses of the qPCR-positive isolates identified genotype 1 of D. fragilis as predominant in budgerigars. Phylogenetic analyses of the SSU rRNA gene region clustered D. fragilis genotypes, as well as other trichomonads, in separate monophyletic clusters with bootstrap values ≥79.0. Our study provides the first evidence for the natural host status of pet budgerigars for D. fragilisand contributes to the knowledge of the epidemiology of this parasite. The high prevalence of genotype 1 of D. fragilis suggests that pet budgerigars are suitable reservoirs for zoonotic transmission. Our findings contribute to an increased awareness and knowledge of D. fragilis infections in the context of a one-health approach., (© 2022 Wiley-VCH GmbH.)

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., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Objective: Dientamoeba fragilis ( D. fragilis ) is a flagellated protozoan with an amoeba-like morphology, located in the gastrointestinal tract. The hypothesis was that the parasite was transported by Enterobius vermicularis ( E. vermicularis ) eggs. This study aimed to determine the association of D. fragilis and E. vermicularis with the genotypes of the identified strain of D. fragilis . Results of trichrome staining were compared with those of polymerase chain reaction (PCR), which is widely used in the diagnosis of D. fragilis ., Methods: A total of 391 samples were obtained. The stool and cellophane slide samples were sent together to the Parasitology Department Laboratory, Faculty of Medicine, Aydın Adnan Menderes University, between 1 October 2017 and 1 October 2018. Stool samples of all patients with E. vermicularis (n=74) and without E. vermicularis (n=74) infection were used. All samples were examined for the presence of D. fragilis by trichrome staining and PCR. The 18S ribosomal RNA region of D. fragilis isolates was sequenced. Demographic characteristics and clinical findings of the patients were evaluated., Results: D. fragilis was detected in 42 (28.37%) of 148 samples; 28 (66.6%) of them were detected in patients with E. vermicularis infection. The coexistence of two parasites was significant (p<0.05). All isolates sequenced were genotype 1. No significant relationship was found between the presence of parasites and clinical findings, living area and gender (p>0.05)., Conclusion: D. fragilis is frequently associated with E. vermicularis , so the presence of D. fragilis should be also considered in affected patients. The use of high-sensitivity molecular methods such as PCR is important in preventing false results., Amaç: Dientamoeba fragilis ( D. fragilis ), amip benzeri morfolojiye sahip, gastrointestinal yerleşimli, kamçılı bir protozoondur. Parazitin Enterobius vermicularis ( E. vermicularis ) yumurtalarıyla taşındığı hipotezi kabul görmektedir. Çalışmamızda D. fragilis ve E. vermicularis birlikteliğini incelemek, bulunan D. fragilis ’lerin genotiplerini belirlemek ve D. fragilis tanısında yaygın olarak kullanılan trikrom boyama ile polimeraz zincir reaksiyon (PZR) yöntemlerini karşılaştırmak amaçlanmıştır., Yöntemler: Çalışmamızda Aydın Adnan Menderes Üniversitesi Tıp Fakültesi, Parazitoloji Laboratuvarı’na 1 Ekim 2017-1 Ekim 2018 tarihleri arasında dışkı ve selofan lam örneği birlikte gönderilmiş toplam 391 olgu örneği incelenmiştir. Selofanlı lam örneklerinde E. vermicularis saptanan tüm gönüllü olguların (74 olgu) dışkı örneği ile E. vermicularis negatif 74 olgunun dışkı örneği çalışılmıştır. Tüm dışkılar trikrom boyama ve PZR yöntemleri ile D. fragilis varlığı açısından incelenmiştir. Saptanan D. fragilis izolatlarının 18S ribozomal RNA bölgesi sekanslanmıştır. Olguların demografik özellikleri ve kliniği değerlendirilmiştir., Bulgular: Toplam 148 olgunun 42’sinde (%28,37) D. fragilis saptanmıştır. D. fragilis pozitif olan 42 olgunun %66,6’sını E. vermicularis pozitif olgular oluşturmuş ve iki parazitin birlikteliği anlamlı bulunmuştur (p<0,05). Sekanslanan tüm izolatlar genotip 1 olarak saptanmıştır. Klinik bulgular, yaşanılan bölge ve cinsiyet ile parazit varlığı arasında anlamlı bir ilişki saptanamamıştır (p>0,05)., Sonuç: Araştırmamızda D. fragilis ’in sıklıkla E. vermicularis ile birliktelik gösterdiği ve bu olgularda D. fragilis varlığına ayrıca dikkat edilmesi gerektiği vurgulanmıştır. Yanlış sonuçları engellemede, yüksek duyarlılığa sahip PZR gibi yöntemlerin önemi bir kez daha görülmüştür.

In order to provide additional data on the prevalence and genetic diversity of Dientamoeba fragilis in human populations, we conducted a study in children from low-income communities in Sao Paulo State, Brazil. Fecal samples from daycare center attendees up to 6 years old (n=156) and staff members (n=18) were submitted to PCR and sequencing of D. fragilis as well as to microscopic examination for the presence of other intestinal parasites. All children assessed were asymptomatic and 10.3% (16/156) were positive for D. fragilis. No worker was found to be positive. An association between Dientamoeba and coinfection with other intestinal parasites was observed. Concerning the genetic diversity, 14 and only two isolates were genotype 1 and genotype 2, respectively. Our findings outline interesting aspects: (1) asymptomatic children as carriers of Dientamoeba in communities in which environmental conditions ensure parasite transmission and, (2) association between Dientamoeba infection in young children and coinfection with other enteric parasites, reinforcing its transmission via the fecal-oral route.

Dientamoeba fragilis is an intestinal protozoan, an inhabitant of the human gastrointestinal tract, with a worldwide distribution. The reported prevalence of D. fragilis varies worldwide in different populations between 0.3% and 82.9%, and its role as a pathogen is still unclear. The parasite has been identified in the faeces of asymptomatic patients and with different acute and chronic symptoms, like abdominal pain, diarrhoea, flatulence, nausea and vomiting. The aims of this study were to evaluate the prevalence of D. fragilis in the North-East of Italy, and the clinical improvement of symptoms after recommended treatment with paromomycin or metronidazole. Furthermore, a literature review of D. fragilis prevalence studies in Italy was carried out to show the Italian situation. Of 575 enrolled people, 85 (14.8%) were positive for D. fragilis. The most prevalent symptoms were abdominal pain 28.2%, anal itching 27.1%, watery diarrhoea 18.8%, meteorism 16.5% and nausea/lack of appetite 14.1%. The high rate of anal itching was unexpected, because it wasn't a common symptom. 32 patients were co-infected with B. hominis (37.7%) and three with G. lamblia (3.5%). Our study showed paromomycin had a high efficacy for treatment of D. fragilis infections 100.0% (45/45), while caution must be used when using metronidazole 53.3% (24/40). We recommend paromomycin for empirical treatment, given its great effectiveness in our population., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In most developing countries, Dientamoeba fragilis infection is an obscure protozoan infection. We aimed to determine a frequency and clinical importance of D. fragilis infection in Taif, Saudi Arabia. A 1-year case control study included patients with gastrointestinal (cases, n=114) or non-gastrointestinal symptoms (controls, n=90). The fecal samples were examined with the classical parasitological methods for intestinal protozoa, and by real time PCR for D. fragilis. The infection by D. fragilis was detected in 5.8% by PCR and in 4.4% patients by microscopy. The infection was identified more in control group (n=9) than in cases (n=3); a sole infection in 11 patients and mixed with Giardia in 1 patient. The other enteric parasites detected were Blastocystis sp. (8.3%), Giardia sp. (5.3%), Cryptosporidium sp. (2.9%), Entamoeba histolytica (1.4%), Entamoeba coli (0.9%) and Hymenolepis nana (0.4%). Our results tend to reinforce the need to increase awareness of D. fragilis infection in Saudi Arabia.

The actual role of Dientamoeba fragilis and Blastocystis in patients with gastrointestinal symptoms is still under debate. A multicenter case-control study was performed in The Netherlands to elucidate the clinical relevance of molecular diagnostics results in gastroenteritis (GE). Samples from this case-control study were used to perform a detailed analysis on the presence of D. fragilis and Blastocystis in relation to gastrointestinal symptoms. In the present study, a real-time PCR for Blastocystis was performed on 1374 case samples and 1026 control samples from the multicenter gastroenteritis case-control study previously tested for D. fragilis. Prevalence of both micro-organisms was highest in children under 20 years of age and lowest in the oldest age group. A significantly lower overall detection of D. fragilis and Blastocystis was found in cases (both 25.8%) as compared to controls (37.6% and 40.0%, respectively). The difference for D. fragilis was statistically significant for subjects above 20 years of age. For Blastocystis, the difference was statistically significant in all age groups, except in children less than 5 years of age. A negative relation between D. fragilis-positive cases and diarrhea was found in this study population. More GE symptoms were reported in cases without D. fragilis or Blastocystis. In the present study, prevalence of both D. fragilis and Blastocystis is lower in cases with gastroenteritic symptoms than in controls. Besides, in cases with D. fragilis or Blastocystis, no association is shown between any of the GE symptoms. Interestingly, this suggests that the presence of these protozoans may be considered characteristic of a healthy intestinal microbiome.

Objectives: This study aimed to (i) determine risk factors for enteropathogen co-infections, (ii) determine whether enteropathogen co-infections influence gastroenteritis risk, and (iii) determine whether enteropathogen co-infection occurred randomly in preschool children., Methods: A monthly-repeated cross-sectional survey in Dutch children aged 0-48 months was conducted during October 2012 to October 2014. A total of 981 stool samples were collected along with questionnaires collecting data on gastrointestinal symptoms and potential risk factors; 822 samples were successfully tested for 19 enteropathogens using real-time multiplex PCRs. Logistic regression analysis assessed co-infections in relation to gastroenteritis and potential risk factors., Results: In all, 598/822 (72.7%) stool samples tested positive for at least one enteropathogen, of which 290 (48.5%) were positive for two or more enteropathogens. Risk factors for two or more enteropathogen co-infections were young age (<12 months, OR 1.9, 95% CI 1.1-3.3; 13-36 months, OR 1.7, 95% CI 1.1-2.5, versus 37-48 months), day-care attendance (OR 1.8, 95% CI 1.3-2.5), households with three or more children versus those with one child (OR 1.7, 95% CI 1.1-2.8). Stool samples collected in spring less often had two or more enteropathogens versus summer (OR 0.4, 95% CI 0.2-0.7). Food allergy was a risk factor for three or more enteropathogen co-infections (OR 3.2, 95% CI 1.1-8.9). The frequency of co-infection was higher than expected for norovirus GI/norovirus GII, Clostridium difficile/norovirus GI, C. difficile/rotavirus, astrovirus/Dientamoeba fragilis, atypical enteropathogenic Escherichia coli/adenovirus, typical enteropathogenic E. coli/adenovirus, and enteroaggregative E. coli/astrovirus. No co-infection was associated with increased gastroenteritis risk., Conclusions: Risk factors for enteropathogen co-infections were identified and specific enteropathogens co-occurred significantly more often than expected by chance. Enteropathogen co-infections were not associated with increased gastroenteritis risk, calling into question their clinical relevance in preschool children., (Copyright © 2018 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

BackgroundDespite the global distribution of the intestinal protozoan Dientamoeba fragilis, its clinical picture remains unclear. This results from underdiagnosis: microscopic screening methods either lack sensitivity (wet preparation) or fail to reveal Dientamoeba (formalin-fixed sample).AimIn a retrospective study setting, we characterised the clinical picture of dientamoebiasis and compared it with giardiasis. In addition, we evaluated an improved approach to formalin-fixed samples for suitability in Dientamoeba diagnostics.MethodsThis study comprised four parts: (i) a descriptive part scrutinising rates of Dientamoeba findings; (ii) a methodological part analysing an approach to detect Dientamoeba -like structures in formalin samples; (iii) a clinical part comparing demographics and symptoms between patients with dientamoebiasis (n = 352) and giardiasis (n = 272), and (iv) a therapeutic part (n = 89 patients) investigating correlation between faecal eradication and clinical improvement.ResultsThe rate of Dientamoeba findings increased 20-fold after introducing criteria for Dientamoeba -like structures in formalin-fixed samples (88.9% sensitivity and 83.3% specificity). A further increase was seen after implementing faecal PCR. Compared with patients with giardiasis, the symptoms in the Dientamoeba group lasted longer and more often included abdominal pain, cramping, faecal urgency and loose rather than watery stools. Resolved symptoms correlated with successful faecal eradication (p < 0.001).ConclusionsPreviously underdiagnosed, Dientamoeba has become the most frequently recorded pathogenic enteroparasite in Finland. This presumably results from improved diagnostics with either PCR or detection of Dientamoeba -like structures in formalin-fixed samples, an approach applicable also in resource-poor settings. Symptoms of dientamoebiasis differ slightly from those of giardiasis; patients with distressing symptoms require treatment.

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., Competing Interests: Competing interests: PFvR received financial support from BÜHLMANN Laboratories AG (Schönenbuch, Switzerland) for other ongoing trials., (© Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: Intestinal infections are common in the elderly, presented with atypical symptoms and may be the cause of mortality with a more severe clinical manifestation. The weakening of cellular and humoral immunity by aging affects the intestinal flora and increases the risk of infection in the presence of chronic diseases. The aim of this study was to investigate the presence of possible parasitic agents in the intestinal system of ≥65-year-old nursing home residents through fecal examination, and to determine the demographic features (age and gender) of this elderly group., Methods: A total of 82 stool samples were examined (100x, 40x) with saline and iodine preparations, formol-ethyl acetate concentration process, trichrome and modified Erlich Ziehl Neelsen stained preparations., Results: One or more parasitological agents were detected in 17 (20.7%) of the 82 stool samples examined. The most common agent was Blastocystis spp. (13.4%), followed by Cryptosporidium spp. (2.4%) and Dientamoeba fragilis (2.4%)., Conclusion: In this study, it was determined that attention should be given to elderly population with regard to intestinal parasitic infections. Because of changes in the immune system, more opportunistic factors could be detected. More frequent screening in public areas such as nursing homes is important for preventing infections.

Introduction: The characteristics of D. fragilis infection are described, with special focus on the clinical and epidemiological aspects., Materials and Methods: A retrospective and descriptive study was performed, including all the patients with Dientamoeba fragilis infection who attended a specialized unit between January 2012 and December 2017. PCR was used to diagnose D. fragilis. Patients were treated with metronidazole or paromomycin and reviewed at four and eight weeks post-treatment. Cure was defined as the negativization of all parasitological tests, in absence of symptoms., Results: 163 patients were diagnosed. The most frequent symptoms were abdominal pain (36.2%), chronic diarrhoea (12.3%), anal itching (10.4%), abdominal discomfort (9.2%), skin disease (8%), acute diarrhoea (4.3%) and vomiting (4.3%). Fifty patients were asymptomatic. Forty-two patients had eosinophilia in blood. Thirty-eight cases (23.3%) had a coinfection by Enterobius vermicularis. One hundred and seven patients received treatment, sixty-one of them with metronidazole and the rest with paromomycin. Ninety-nine patients (91%) were cured. The rate of cure was 100% in the paromomycin group versus 86.8% in the metronidazole group (p=0.005; OR: 1.173 [1.057-1.302]). The absence of cure was associated with E. vermicularis coinfection (p=0.014; OR: 6.167 [1.432-26.563] and with longer duration of the symptoms (175 [±159SD]) versus 84 [±88SD] days, p=0.014) but multivariable analysis did not confirm these associations., Conclusion: Dientamoeba fragilis is an important and underestimated cause of gastrointestinal disease in both the autochthonous and immigrant or traveller population. More studies are needed to clarify its optimal treatment and the role played by E. vermicularis in its transmission and maintenance., (Copyright © 2018 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.)

Dientamoeba fragilis is a gastrointestinal trichomonad parasite whose pathogenicity is yet to be determined. The difficulty involved in microscopically diagnosing D. fragilis in feces led to the development of real-time PCR methodologies for the detection of D. fragilis in stool samples. Prevalence studies in Europe show much higher levels of infection where a laboratory-developed real-time assay is the predominant assay for the detection of Dientamoeba fragilis than in regions that use the EasyScreen assay for detection of gastrointestinal pathogens. The aim of this study was to compare a commercially available Dientamoeba fragilis assay (Genetic Signatures EasyScreen assay) to a widely used laboratory-developed real-time PCR method. Two hundred fifty fecal samples were screened using the laboratory-developed real-time assay on four real-time PCR platforms producing a number of discrepant results. Limit-of-detection studies were undertaken to attempt to resolve sensitivity for each platform tested. The presence or absence of Dientamoeba fragilis DNA in discrepant samples was shown using PCR amplicon next-generation sequencing. Eukaryotic 18S diversity profiling was conducted on discrepant samples to identify the presence or absence of additional protozoan species in samples that may be responsible for cross-reactivity seen in these samples. The results revealed the potential for multiple false-positive results when using the laboratory-developed real-time assay across multiple real-time platforms using manufacturer default settings. This report provides recommendations to resolve these issues where possible and suggestions for future prevalence studies, and it emphasizes the EasyScreen assay as the molecular method of choice as well as the need for standardization of detection assays across all nations screening for D. fragilis ., (Copyright © 2019 American Society for Microbiology.)

Background: Dientamoeba fragilis is a protozoan parasite of the human gastrointestinal tract and still controversial in association with gastrointestinal symptoms., Purpose: We present cross-sectional study of the prevalence of D. fragilis, and sociodemographic and clinical features in the patients with gastrointestinal symptoms., Methods: A total of 490 fecal specimens were collected from outpatients with gastrointestinal symptoms in the Department of Parasitology, Faculty of Medicine, Ege University and Celal Bayar University, Turkey. Fecal specimens were examined with microscopy and inoculated in Robinson medium. D. fragilis-positive samples were examined for the presence of other intestinal parasites using enzyme immunoassay. Real-time PCR analysis was performed on all samples., Results: Of the 490 stool specimens examined by real-time PCR, 59 patients were positive for D. fragilis infection with prevalence rate of 12.04%. Forty-four of positive patients (74.5%) were found to be infected with only D. fragilis, while 23.7% were co-infected with Blastocystis and 1.7% were co-infected with Rotavirus. No statistically significant difference was found in all the examined patients in terms of D. fragilis positivity for all sociodemographic parameters. Loose stool consistency was associated with the presence of D. fragilis, with 18.3% (P = 0.001). When the clinical symptoms of all the patients participating in this study were examined, diarrhea was statistically more significant in patients with the presence of D. fragilis (16.3%; P = 0.001). The rate of diarrhea in D. fragilis-positive patients (84.09%; P = 0.0005) was higher than that of D. fragilis-negative patients and it was statistically significant., Conclusion: This study is important for assessing the prevalence of D. fragilis and its association with other factors in symptomatic patients in a large sample group in Turkey, as well as investigating the relationship of identified symptoms with the D. fragilis pathogenicity. It is suggested that D. fragilis in this case is not a commensal parasite but a pathogenic parasite and that the most common clinical symptom is diarrhea.

In this study we characterized the presence and subtype (ST1-ST4) of Blastocystis in patients attended at a referral center for tropical diseases in Northern Italy. We also, evaluated the organism's association with other intestinal parasites. Parasite screening was performed on 756 patients, from different geographical origins (namely, Italians, Africans, South Americans, Asian and non-Italian Europeans) in which Italians represented the largest group. Blastocystis was seen to be the most prevalent parasite in the study. Subtype 3 and 1 were the most frequently found in the Italians and Africans. Our data confirmed previous studies performed in Italy, in which ST3 proved to be the most prevalent subtype, but we highlighted also a high frequency of mixed subtypes, which were probably underestimated in former analyses. Interestingly, the mixed subtypes group was the most prevalent in all the analysed geographical areas. About half of our cases showed other co-infecting parasites and the most frequent was Dientamoeba fragilis. Our study confirms that, in Blastocystis infection, multiple subtypes and co-infecting parasites are very frequently present, in particular Dientamoeba fragilis., Competing Interests: The authors have declared that no competing interests exist.

Dientamoeba fragilis is an intestinal protozoan, usually considered nonpathogenic. However, in the last years, there has been an attempt to clarify its possible pathogenic role. We aim to evaluate the clinical and epidemiological characteristics of D. fragilis -infected patients. Adults with D. fragilis detection in feces who attended the Vall d'Hebron University Hospital (Barcelona, Spain) were evaluated retrospectively from April 2009 to March 2014. We classified the patients in asymptomatic, symptomatic without other causes except infection of D. fragilis , and symptomatic with another cause. Among symptomatic patients, treatment response was evaluated. One hundred eight patients were included. Sixty-three percent of the patients were immigrants, 29.6% were autochthonous, and 7.4% were travelers. Forty-nine (45.3%) patients presented symptoms, and eosinophilia was observed in 26 (24.1%) patients. Overall, 59 (54.7%) patients were asymptomatic, 15 (13.8%) presented symptoms which were attributable to other causes, and 34 (31.5%) patients presented symptoms with no other causes. In this last group, 29 patients received specific treatment and 65.5% of them presented a complete resolution of the symptoms. The group of symptomatic patients with no other cause had more proportion of women, more proportion of autochthonous people, and were older compared with the group of asymptomatic patients. Dientamoeba fragilis infection should be considered as pathogenic when other causes are ruled out.

Introduction: The results of a study on the household contacts of patients with D. fragilis infection are presented., Methods: A prospective, descriptive study was carried out on all Dientamoeba fragilis-infected patients treated at the Tropical Medicine Unit of Hospital Universitario Central de Asturias between 2012- 2017 and their household contacts. Three stool samples per patient and three stool samples from each of their household contacts were concentrated and analysed. Polymerase chain reaction (PCR) was used to detect the presence of D. fragilis in all stool samples. Co-infection with E. vermicularis was studied in both groups. Patients and contacts who failed to deliver one or more samples for diagnosis and patients without household contacts were excluded., Results: 44 Patients infected with D. fragilis, as well as their 97 household contacts were enrolled. 50.5% of household contacts had a positive PCR for D. fragilis. 20 were also coinfected with E. vermicularis. The presence of infection was significantly more frequent in patients with children (34/15 versus 24/24; p= 0.064; OR: 2.267 [0.988-5.199]), E. vermicularis infection in the children being 20/29 versus 0/48 (p=0.0001), and in another family member being 29/20 versus 15/33 (p=0.008; OR: 3.190 [1.384-7.352])., Conclusions: The prevalence of D. fragilis infection in household contacts was high. It was associated with the presence of children in the family nucleus and coinfection with E. vermicularis irrespective of gender, age, rural area or contact with animals., (Copyright © 2017 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.)

The flagellated protozoan Dientamoeba fragilis is one of the most commonly diagnosed parasite of the human gut, with a global distribution. Nevertheless, essential aspects of its biology remain incompletely understood or controversial, most notably life cycle, host range, transmission routes and the ability to cause disease. Molecular epidemiologic studies are also scarce, and limited by the lack of informative genotyping tools. To date, two D. fragilis genotypes (1 and 2) are recognized, with a strong predominance of genotype 1 in both humans and few animal hosts. Recent studies have shown that a very low level of genetic variability characterizes parasite isolates collected in various geographic areas and from both symptomatic and asymptomatic cases. This has raised the hypothesis D. fragilis may be a clonal organism. The recent availability of transcriptome data should greatly assist the development of markers useful to understand genetic diversity of D. fragilis at the population level., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Pediatric diarrhea is a common cause of death among children under 5 years of age. In the current study, we investigated the frequency of intestinal parasites among 580 pediatric patients with chronic diarrhea. Parasitic protozoa (all species combined) were detected by molecular tools in 22.9% of the children and the most common parasite was Cryptosporidium spp. (15.1%). Blastocystis hominis was detected in 4.7%, Dientamoeba fragilis in 4%, Giardia duodenalis in 1.7%, and Entamoeba histolytica in 0.17%. Protozoan infections were observed among all regional groups, but prevalence was highest among Qatari subjects and during the winter season. Typing of Cryptosporidium spp. revealed a predominance of Cryptosporidium parvum in 92% of cases with mostly the IIdA20G1 subtype. Subtypes IIdA19G2, IIdA18G2, IIdA18G1, IIdA17G1, IIdA16G1, and IIdA14G1 were also detected. For Cryptosporidium hominis , IbA10G2 and IbA9G3 subtypes were identified. This study provides supplementary information for implementing prevention and control strategies to reduce the burden of these pediatric protozoan infections. Further analyses are required to better understand the local epidemiology and transmission of Cryptosporidium spp. in Qatar.

Dientamoeba fragilis is an intestinal protozoan of debated clinical significance. Here, we present cross-sectional and longitudinal observations on D. fragilis in children aged 0 to 6 years from a 1-year multi-day-care-center cohort study set in Copenhagen, Denmark. The inclusion period for the cohort was 2009 through 2012. Stool samples collected from the children were accompanied by questionnaires completed by the parents or guardians of the children. Using real-time PCR, D. fragilis was detected in the first stool sample from 97 of 142 (68.3%) children. We evaluated the associations between seven plausible risk factors (age, sex, having siblings, having domestic animals at home, having had infant colic, recent history of intake of antibiotics, and recent history of travel abroad) as well as six reported symptoms (lack of appetite, nausea, vomiting, abdominal pain, weight loss, and diarrhea) and testing positive for D. fragilis The final multivariable model identified being >3 years old and having a history of recent travel abroad as risk factors for testing positive for D. fragilis Moreover, univariable analyses indicated that having siblings was a risk factor. There was no statistical association between a recent history of gastrointestinal symptoms and testing positive for D. fragilis Among the 108 children who were represented by ≥2 samples and thus included in the longitudinal analysis, 32 tested negative on the first sample and positive later, and the last sample from each of the 108 children was positive. The results are in support of D. fragilis being a common enteric commensal in this population., (Copyright © 2017 American Society for Microbiology.)

Background: Dientamoeba fragilis is commonly identified in children in primary care and is suspected to cause gastrointestinal disease., Objective: To determine the association between D. fragilis colonization and gastrointestinal symptoms in children., Methods: We performed a cross-sectional study with children who presented in primary care with gastrointestinal symptoms. The associations between D. fragilis colonization and specific symptoms were explored by means of logistic regression analyses. Asymptomatic siblings of these cases were invited as control subjects for a case-control analysis, where we explored the association between D. fragilis and gastrointestinal symptoms with conditional logistic regression analysis., Results: In the cross-sectional study, 107 children were included. Their median age was 9 years (interquartile range = 6-12) and 38 (35.5%) were boys. Colonization of D. fragilis was present in 59 children (55.1%). The absence of D. fragilis was associated with soft to watery stool [odds ratio (OR) = 0.29; 95% confidence interval (CI) = 0.10-0.85], chronic diarrhoea (OR = 0.42; 95% CI = 0.18-0.97) and fatigue (OR = 0.45; 95% CI = 0.20-0.99). The case-control analyses included 44 children in each group. Dientamoeba fragilis colonization was not observed more often in cases than in controls after adjustment for age and sex (OR = 1.02; 95% CI = 0.28-3.65)., Conclusion: Dientamoeba fragilis is a common parasite in children with and without gastrointestinal symptoms. The anomalous finding of the association between the absence of D. fragilis with soft to watery stools, chronic diarrhoea and fatigue are inexplicable. Our study suggests that D. fragilis colonization does not increase the risk for gastrointestinal symptoms., (© The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Dientamoeba fragilis is a single-celled protozoan, closely related to the trichomonads. Reported worldwide as causing human gastrointestinal symptoms, D. fragilis is very common and is second only to Blastocystis spp. Dientamoebiasis equals or exceeds the incidence of giardiasis. This minireview includes diagnostic options, clinical relevance, therapy, an animal model, the confirmed cyst stage, and sequencing data. The development of a rodent model, fulfilling Koch's postulates, and the confirmation of a cyst stage have clarified transmission routes, including fecal-oral transmission. The prevalence of D. fragilis varies between 0% to over 82%; results depend on the geographic location, group studied, and diagnostic methods used., (Copyright © 2016, American Society for Microbiology. All Rights Reserved.)

Dientamoeba fragilis is a protozoan with a debated role in gastrointestinal (GI) disease. Although correlated to GI symptoms, no virulence factors have been described. In this study, we evaluated the cause of GI symptoms in children at two schools, with children aged 1 to 10 years, in the county of Jönköping, Sweden. D. fragilis infection correlated to GI symptoms in children and Enterobius vermicularis correlated to D. fragilis infection.

Dientamoeba fragilis is an inhabitant of human gastrointestinal tract with a worldwide distribution. The first description considered this protozoan a rare and harmless commensal, since then it has struggled to gain recognition as a pathogen. Commercial multiplex real-time PCR was used to detect D. fragilis in fecal samples from hospitalized children (⩽18 years) with acute gastrointestinal disease, admitted to two hospitals of Lisbon area, with different demographic characteristics. A total of 176 children were studied, 103 (58·5%) male, 144 (81·8%) children between 0 and 5 years and 32 (18·2%) above 6 years old. The overall protozoa frequency considering the four tested microorganisms were 8·5% (15/176), and the most frequently found protozoan was D. fragilis, 6·3% (11/176). Dientamoeba fragilis frequency was higher among older children (21·9%), than younger children (2·8%), and greater in boys (6·8%) than in girls (5·5%). All positive children presented with diarrhoea associated with vomiting, fever and abdominal pain. Infection was associated with the age of children (P < 0·001), school attendance (P = 0·002) and consumption of certain foods (P = 0·014), e.g. cakes with crème and ham. The frequency of diantamoebiasis found in a cohort of hospitalized Portuguese children, with acute gastrointestinal disease, could be considered a very high value when compared with the protozoan frequency normally associated with this pathology.

Dientamoeba fragilis is a trichomonad parasite that can infect the gastrointestinal tract of humans causing gastrointestinal disease. Little is known about its epidemiology. We evaluated the prevalence of D. fragilis by conducting a cross sectional study of an Orang Asli population in rural Malaysia. We examined stool samples from 150 participants for D. fragilis using Wheatley's trichrome stain and collected demographic data from each participant using a structured questionnaire. Five participants (3.3%) had D. fragilis in their stool; four of these were aged < 15 years; 3 were male and 2 were female. All participants with positive stool sample for D. fragilis were symptomatic; 3 had diarrhea and 2 had other gastrointestinal symptoms. D. fragilis is present in the study population. Further studies are needed to determine the virulence, pathogenicity and mode of transmission of D. fragilis in the study population.

Associations between antimicrobial use and risk of enteric infection with intestinal protozoa are scarcely studied. The aim of this study was to quantify the risk of Dientamoeba fragilis infection conferred by exposure to antimicrobials. We conducted a registry-based retrospective cohort study of 9,945 Danish patients investigated for D. fragilis infection between 2008 and 2011, using data from the Danish Register of Medicinal Product Statistics, and calculating relative risks (RR) for D. fragilis infection by stratified binary regression. Furthermore, we conducted a population based case-control study using controls sampled from the Danish Civil Registration System, calculating hazard ratios (HR) for D. fragilis infection by conditional logistic regression. Exposure to metronidazole was found to confer decreased risk of D. fragilis infection; however, similar associations were found for antimicrobials not commonly used to treat D. fragilis, such as broad-spectrum penicillin, fluoroquinolones, and macrolides. In contrast, mebendazole exposure was associated with increased risk. The intake of antimicrobials influences the risk of D. fragilis.

Background & Aims: The parasites Dientamoeba fragilis and Blastocystis have been detected in feces from patients with irritable bowel syndrome (IBS), therefore these parasites may be involved in IBS pathogenesis. We proposed that a higher prevalence of the parasites in IBS subjects compared with asymptomatic controls would support such a mechanism. We aimed to determine the prevalence of these parasites in IBS subjects (cases) and controls and to identify risk factors associated with parasite carriage., Methods: We performed a population-based, case-control study of an adult population from an internet-based research institute in Denmark. In January 2010, subjects completed a questionnaire based on the Rome III criteria for IBS and answered questions on factors associated with parasite carriage. Respondents (n = 483) were asked to submit fecal samples for parasite testing; samples were analyzed from 124 cases and 204 controls., Results: A greater proportion of controls than cases carried the parasites (50% vs 36%; P = .01). D fragilis was detected in a greater proportion of fecal samples from controls than cases (35% vs 23%; P = .03), as was Blastocystis (22% of controls vs 15% of cases; P = .09), and a greater percentage of controls carried more than 1 species of parasite (16% of controls vs 8% of cases; P = .05). D fragilis infection was associated with having children 5 to 18 years old in the household and Blastocystis infection was associated with high income (≥600,000 Danish Kroner/y, approximately $100,000 US dollars/y), no animals in the household, and drinking bottled water., Conclusions: D fragilis and Blastocystis were detected in a greater proportion of fecal samples from the asymptomatic background population in Denmark than from subjects with IBS symptoms. These findings indicate that these parasites are not likely to have a direct role in the pathogenesis of IBS. Longitudinal studies are required to understand their role in gastrointestinal health., (Copyright © 2015 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Purpose of Review: To highlight new findings on the relevance of gastrointestinal protozoan infections to global public health in low-income and middle-income countries and suggest new large-scale interventions., Recent Findings: New disease burden assessments and epidemiological studies highlight the role of the major intestinal protozoa as important etiologic disease agents in low-income and middle-income countries. Despite their prevalence and adverse health impact, such information has not yet translated to the implementation of large-scale interventions as exist for helminth infections and other neglected tropical diseases. There are also several key research and development questions that must be addressed for intestinal protozoan infections and the potential need for new tools, for example, drugs, diagnostics, and vaccines. Additional studies have identified new and emerging species of intestinal protozoa relevant to global public health such as Dientamoeba fragilis and Blastocystis hominis and how they too might emerge as important gastrointestinal pathogens in the coming years., Summary: New and emerging information on intestinal protozoa are reviewed with emphasis on aspects considered relevant to global health policymakers including prospects for scaling up interventions against intestinal protozoan infections in resource-poor countries.

The intestinal protozoon Dientamoeba fragilis remains a clinical entity of dubious significance. While several previous studies address questions of epidemiology, only a handful have systematically employed and reported on the results from real-time polymerase chain reaction (qPCR), the best currently available diagnostic modality, and the comparison of results from different studies is, therefore, difficult. Since 2007, Statens Serum Institut (Denmark) has utilised qPCR for D. fragilis as routine diagnostic work-up for intestinal parasitosis, testing more than 22,000 samples from 2008 through 2011, and the aim of this study was to report on the results and experiences gained in the process. We demonstrate a staggeringly high proportion (43%) of investigated patients positive for D. fragilis, ranging from 12 to 71% depending on age group, showing a bimodal age distribution peaking in children and adults of parental age, as well as a clear association between exposure to children and risk of D. fragilis infection. We discuss these findings in light of the pinworm egg vector hypothesis and substantiate further our knowledge of risk factors pertaining to D. fragilis carriage.

Objective: To search for the opportunistic and other pathogenic intestinal parasites in dialysis patients, and to compare the methods used for diagnosis., Methods: This is a randomized study, which recruited participants from the dialysis patients. The study was carried out in the Department of Microbiology, Research Hospital, School of Medicine in Kocaeli University, Kocaeli, Turkey between June 2012 and March 2013. One hundred and forty-two patients were diagnosed with an end-stage renal failure, which underwent dialysis, and 150 healthy volunteers were enrolled in the study. Native-lugol, formol ethyl acetate sedimentation method, trichrome, modified trichrome, acid fast, and Calcofluor staining methods were applied to the stool samples. For the diagnosis of Cryptosporidium spp., Giardia intestinalis (G. intestinalis), and Entamoeba histolytica (E. histolytica), commercially available ELISA kits were used, which detect antigen in the stool., Results: Parasites were found in 62 of the dialysis patients (43.7%) and 19 of the control group (12.7%). The most encountered parasitic agents in the dialysis patients were Blastocystis spp. (23.9%), G. intestinalis (8.5%), E. histolytica (2.1%), Microsporidia spp. (2.1%), and Cryptosporidium spp. (2.1%). The parasite detection rate of the formol ethyl acetate sedimentation method was found to be higher than native-lugol (p<0.05)., Conclusion: To protect the dialysis patients with diarrhea from parasitic infections, it is important to carry out interval stool examinations with trichrome, modified trichrome, acid fast, and Calcofluor staining methods, and the ELISA method, which detects antigen in the stool.

Endemic parasitic infections in the United States are more frequent than is commonly perceived. Intestinal parasitic infection with Cryptosporidium, Dientamoeba, and Giardia occurs most often in children in northern states during the summer months. Zoonotic Toxocara and Toxoplasma parasitic infections are more frequent in southern states, in African Americans, and in populations with lower socioeconomic status. Approximately 300, 000 people in the United States have Trypanosoma cruzi infection. Local, vector-borne transmission of T cruzi and Leishmania infections has been documented in southern states. Parasitic diseases endemic to the United States are not uncommon but are understudied., (Copyright © 2013 Elsevier Inc. All rights reserved.)

In recent years, interest in Dientamoeba fragilis on the part of biologists, clinicians and parasitologists has increased considerably due to the need to clarify the many unresolved issues related to the parasite and the associated infection. This paper aims to provide a summary of the state of knowledge of D. fragilis in its different aspects, and, through the analysis of the literature and the most recent data, the present review aims to record the reasons why this protozoan, although little known, should not be underestimated in the diagnosis of human parasitic infections also in Italy.

Dientamoeba fragilis is a pathogenic protozoan parasite that is implicated as a cause of human diarrhoea. A case-controlled study was conducted to determine the clinical signs associated with D. fragilis infection in children presenting to a Sydney Hospital. Treatment options are also discussed. Stool specimens were collected from children aged 15 years or younger and analysed for the presence of D. fragilis. In total, 41 children were included in the study along with a control group. Laboratory diagnosis was performed by microscopy of permanently stained, fixed faecal smears and by real-time PCR. Gastrointestinal symptoms were present in 40/41 (98%) of these children with dientamoebiasis, with diarrhoea (71%) and abdominal pain (29%) the most common clinical signs. Chronic gastrointestinal symptoms were present in 2% of cases. The most common anti-microbial used for treatment was metronidazole (n=41), with complete resolution of symptoms and clearance of parasite occurring in 85% of cases. A treatment failure rate occurred in 15% of those treated with metronidazole. Follow-up treatment comprised of an additional course of metronidazole or iodoquinol was needed in order to achieve complete resolution of infection and symptoms in this group. This study demonstrates the pathogenic potential of D. fragilis in children and as such it is recommended that all laboratories must routinely test for this organism and treat if detected.

Dientamoeba fragilis is a protozoan that inhabits the human gut. It is approximately 100 years since Dientamoeba's discovery and first description when it was described as a rare and harmless commensal. Since then it has struggled to gain recognition as a pathogen despite the evidence supporting its pathogenicity. Dientamoeba remains neglected, probably due to the misconceptions that it is uncommon and non-pathogenic. Usually, carriage of Dientamoeba is associated with symptoms such as abdominal pain and diarrhea. Moreover, antimicrobial therapy followed by resolution of symptoms coincides with the eradication of Dientamoeba. This manuscript reviews the scientific literature relating to Dientamoeba's prevalence and pathogenicity. While much of the evidence supporting its pathogenicity is only circumstantial, it is apparent that most researchers agree that Dientamoeba is pathogenic. Therefore, in symptomatic patients who harbor Dientamoeba and no other pathogen, Dientamoeba should be considered as the etiological agent and treated as such., (© 2011 Landes Bioscience)

Studies have suggested a possible role for Blastocystis hominis and Dientamoeba fragilis in the etiology of irritable bowel syndrome (IBS). We studied the prevalence of B. hominis and D. fragilis in patients with IBS-diarrhea (IBS-D). Three hundred and thirty patients were enrolled, 171 (52%) with IBS-D and 159 (48%) were controls, respectively. Stool microscopy, culture, and polymerase chain reaction (PCR) for B. hominis and D. fragilis were done. B. hominis was positive by stool microscopy in 49% (83/171) of IBS compared to 24% (27/159) in control (p < 0.001). B. hominis culture was positive in 53% (90/171) in IBS compared to 16% (25/159) in control (p < 0.001). B. hominis PCR was positive in 44% (75/171) in IBS compared to 21% (33/159) in control (p < 0.001). D. fragilis microscopy was positive in 3.5% (6/171) in IBS-D compared to 0.6% (1/159) in control (p = 0.123). D. fragilis culture was positive in 4% (7/171) in IBS compared to 1.3% (2/159) in control (p = 0.176). D. fragilis PCR was positive in 4% (6/171) in IBS-D compared to 0% (0/159) in control (p = 0.030). B. hominis is common, while D. fragilis was less prevalent in our patients with IBS-D. B. hominis and D. fragilis culture had a better yield compared to stool microscopy and PCR.

Among 750 symptomatic and asymptomatic patients, Dientamoeba fragilis was detected at a prevalence of 5.2% and more common than Giardia intestinalis. Most infected patients presented with diarrhea and abdominal pain with symptoms greater than 2 weeks duration being common. Bacterial and viral causes of infection were excluded by routine microbiological techniques. Treatment of D. fragilis infection with either iodoquinol, paromomycin, or combination therapy resulted in the eradication of the parasite and complete resolution of symptoms. Treatment failure/relapses were associated only with the use of metronidazole. Nineteen patients were examined for pin worm, no Enterobius vermicularis, a proposed vector of transmission, were detected. Intermittent shedding of D. fragilis was found to be highly variable. These studies confirm the pathogenic nature of D. fragilis and we recommend laboratories routinely test for the organism.

Two independent studies were conducted to describe symptoms and potential risk factors associated with Blastocystis infection. Isolates were subtyped by molecular analysis. In the NORMAT study (126 individuals randomly sampled from the general population) 24 (19%) were positive for Blastocystis. Blastocystis was associated with irritable bowel syndrome (P=0.04), contact with pigs (P<0.01) and poultry (P=0.03). In the Follow-up (FU) study (follow-up of 92 Blastocystis-positive patients), reports on bloating were associated with subtype (ST) 2 (P<0.01), and blood in stool to mixed subtype infection (P=0.06). ST1 was more common in FU individuals (32%) than in NORMAT individuals (8%), whereas single subtype infections due to ST3 or ST4 were seen in 63% of the NORMAT cases and 28% of the FU cases. Only FU individuals hosted ST7, and ST6/7 infections due to ST7 or ST9 were characterized by multiple intestinal symptoms. The data indicate subtype-dependent differences in the clinical significance of Blastocystis.

A high prevalence of Dientamoeba fragilis is reported in faecal samples collected from patients attending complementary medicine practitioners in the British Isles. Specimens were collected directly after passing into sodium acetate-acetic acid-formalin (SAF). During two observation periods in 2002-04 and 2005-07, a D fragilis prevalence of 14.6% (n = 543) and 16.9% (n = 421), respectively, was recorded. These results confirm a surprisingly high prevalence of D fragilis among a selected population. Clinical information was only available for half of the patients with D fragilis; 50% of requests with clinical information reported gastrointestinal symptoms. For further work on its pathogenic role and prevalence among patients with gastrointestinal symptoms, immediate collection in SAF should be considered the optimal sampling modality for UK based laboratories.

The role of Enterobius vermicularis in the transmission of Dientamoeba fragilis has been evaluated in two groups of patients admitted to the Parasitology Laboratory of Celal Bayar University: one group with E. vermicularis infection (n=187, Pinworm Group), and the other with D. fragilis infection (n=126, Dientamoeba Group). The presence of the other parasite, pinworm or Dientamoeba, was investigated with the microscopic examination of cellophane tape and stool samples for three consecutive days. In the Pinworm Group, 9.6% of the patients were found to be coinfected with D. fragilis, while 25.4% of the patients in the Dientamoeba Group were found to be coinfected with pinworms. The coincidence rates of D. fragilis and E. vermicularis, higher than the prevalence of each parasite in similar populations, suggest a common relation between these two parasites, possibly in entering the human body. E. vermicularis infection was found to be significantly more common in younger children (p<0.001), indicating that younger children may also be at higher risk for D. fragilis infection. These findings also raise the question of whether the unrelated symptoms of the pinworm infected patients such as abdominal pain and diarrhea may actually be due to overlooked Dientamoeba infections.

Dientamoeba fragilis is a gastrointestinal protozoan that has a worldwide distribution and is emergeing as a common cause of diarrhea. As D. fragilis has a propensity to cause chronic illness with symptoms similar to irritable bowel syndrome (IBS) it is not surprising that some patients with D. fragilis are misdiagnosed as having IBS. In contrast to most other pathogenic protozoa very little is known about its life cycle, epidemiology and mode of transmission. What role animal reservoirs play in the transmission of this parasite is unknown. Consequently we undertook a prospective study to determine the host distribution of D. fragilis. Over a 2-year-period, 608 faecal samples from a wide range of animal and bird species, including pigs and other food species, were screened using permanent stained smears for the presence of D. fragilis. Trophozoites of D. fragilis were only detected in Western lowland gorillas (3/10) (Gorilla g. gorilla) and confirmed by PCR targeting the SSU rRNA gene. The limited host range detected suggests human infection may not involve transmission from other animal species. In addition, we provide an update on the limited knowledge about the life cycle of this parasite and its host distribution.

The prevalence of Dientamoeba fragilis in patients from a metropolitan area in Denmark was determined by examination of paired stool samples using two techniques: a formol ethyl-acetate concentration technique with unpreserved faeces and a permanent staining technique on faeces preserved with sodium acetate-acetic acid-formalin (SAF). Using the SAF permanent staining technique and the formol ethyl-acetate concentration technique, 25% and 15% of the specimens, respectively, were parasite-positive. D. fragilis was detected in 12 of the 103 patients, only two of whom harboured other recognised pathogenic parasites. Overall, D. fragilis had a remarkably high prevalence in the metropolitan area of Denmark investigated.

The present study was conducted to determine the prevalence and clinical features of dientamoebiasis in patients presumed to be infected with intestinal parasites. A total of 168 patients were examined for D. fragilis using microscopy (after Wheatley's trichrome staining) and culture (using modified Boeck and Drbohlav's medium). D. fragilis trophozoites were detected in 15 samples (8.9%) examined using trichrome staining and in 50 samples (29.8%) by culture method. Other enteric parasites were common in the study population as 48.8% of patients (82/168) were found harboring intestinal parasites. Blastocystis hominis was the most common, identified in 33.3% (56/168) of the samples. Giardia lamblia was detected in 17.9% (30/168) and E. histolytica/E. dispar in 11.9% (20/168). The symptoms most frequently encountered were diarrhea, abdominal pain and weight loss and fatigue. Diarrhea and abdominal pain were significantly more frequent in patients with dientamoebiasis compared to non pathogenic cases (P < 0.05). Diarrhea was 38.5% of patients infected with D. fragilis compared to 50% of patients infected with G. lamblia, while abdominal pain was encountered with D. fragilis in 41% compared to 33.3% with G. lamblia. These differences were insignificant (P > 0.05).

During 2004, we identified 39 intestinal infections caused by Dientamoeba fragilis and 23 caused by Giardia duodenalis, on 1141 home subjects (3.4% and 2.0% respectively): D. fragilis was observed in 4.5% of O and P (29/644 subjects suffering from aspecific bowel disorders) and in 2.0% of diarrhoeas (10/497); G. duodenalis was observed in 3.1% (20/644) and in 0.6% (3/497) of cases respectively. No other pathogenic parasites were identified (only 1 case of enterobiasis in an asymptomatic child). Commensal protozoa were observed, among O and P, in 4.3% of cases (28/644). The non-pathogenic B. hominis, often associated with other protozoa, was observed in 4.1% of all 1141 cases. D. fragilis is undoubtedly more frequent in adults (36/39 cases, 92.3%) than in children (3/39, 7.7%), and is prevalent among females (24/39, 61.5%) in respect of males (15/39, 38.5%). G. duodenalis is more prevalent among adults (16/23, 69.5%) than children (7/23, 30.5%), but is more frequent among males (13/23, 56.5%) than females (10/23, 43.5%). Clinical correlations of dientamoebiasis and giardiasis are reported, seasonal and epidemiological features of these protozooses are outlined, and the authors emphasize the importance and need of Giemsa stain, among O and P and acute or prolonged diarrhoeas, on the basis of previous good direct microscopic observations of faecal specimens, for correct and complete diagnosis of intestinal infections.