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Concept: Dientamoeba fragilis


Abstract. The role of Dientamoeba fragilis in irritable bowel syndrome (IBS) is incompletely known. We aimed to investigate whether eradication of D. fragilis alleviates symptoms in IBS. Twenty-five D. fragilis-positive IBS patients were treated with Metronidazole (MZ) or Tetracycline. The patients were mostly female (89%), and mean age (SD) was 35.1 (8.2) years. Microbiological response, evaluated 2 weeks post-treatment, was observed in 15 of 25 patients (60%), all by MZ. Clinical response, defined as adequate relief of symptoms, was observed in 7 of 22 patients (32%), all by MZ. In a logistic regression analysis, we found no significant association between clinical and microbiological response. This case study did not support our hypothesis of a simple association between D. fragilis and IBS. Some D. fragilis-infections were insufficiently treated by MZ. Further studies into the prevalence and effect of eradication of D. fragilis in IBS and into efficient treatments of D. fragilis are warranted.

Concepts: Scientific method, Regression analysis, Logistic regression, Irritable bowel syndrome, Dientamoeba fragilis, Dientamoeba


INTRODUCTION:: Dientamoeba fragilis infection in children is common, and its incidence has increased since the introduction of more sensitive molecular techniques. There is no consensus on the optimal treatment. Current medical practice in the Netherlands is to treat symptomatic children with clioquinol or metronidazole. This study attempts to obtain more information about the clinical picture of D. fragilis infection in children and to evaluate responses to both anti parasitic drugs. METHODS:: Children < 18 years of age with a positive stool PCR test for D. fragilis infection were retrospectively evaluated. Clinical data and effectiveness of treatment were analyzed by examining patient's hospital records from the Medical Center Leeuwarden and of stool samples by the Center for Infectious Diseases in Friesland. RESULTS:: We analyzed 238 patients with an average age of 8.5 years (± 4.2 years). Most patients were symptomatic (95.8%) and presented with abdominal pain (72.7%), loose stools (32.8%), and hard stools (24.8%). Co-infection with other gastrointestinal pathogens was present in 29 patients (12.2%). A higher incidence of infection was found in the winter. Clioquinol had a higher clinical success rate than did metronidazole (74.7% vs 55.2%, p=0.047). CONCLUSION:: These results suggest that clioquinol could be more effective than metronidazole in alleviating symptoms of D. fragilis infection in children, but double-blind prospective placebo-controlled studies should be performed before final conclusions can be made.

Concepts: Medicine, Disease, Infectious disease, Netherlands, Dientamoeba fragilis, Dientamoeba


Dientamoeba fragilis has emerged as an important and under recognized cause of gastrointestinal illness. We report a familial cluster of D. fragilis associated with marked peripheral eosinophilia and gastrointestinal symptoms. D. fragilis infection should be considered in the setting of unexplained eosinophilia. If confirmed, screening of household members should be considered.

Concepts: Family, Household, Dientamoeba fragilis


Efficient and easy-to-use DNA extraction and purification methods are critical in implementing PCR-based diagnosis of pathogens. In order to optimize the routine clinical laboratory diagnosis of eukaryotic enteric pathogens, we compare, via quantitative PCR cycle threshold (Ct) values, the efficiency of two DNA extraction kits: the semi-automated EZ1®(Qiagen) and the manual QIAamp®DNA Stool Mini Kit (Qiagen), on six protozoa: Blastocystis spp., Cryptosporidium parvum/hominis, Cyclospora cayetanensis, Dientamoeba fragilis, Giardia intestinalis and Cystoisospora belli and one microsporidia: Enterocytozoon bieneusi.

Concepts: DNA, Parasites, Polymerase chain reaction, Molecular biology, Protozoa, Dientamoeba fragilis, Microsporidiosis, Metamonads


It remains controversial whether Dientamoeba fragilis is a commensal parasite or a pathogen. The objective of this systematic review was to establish the strength of the evidence that Dientamoeba fragilis would cause diarrhea. A search was performed for studies that reported either the association between D. fragilis detection in stools and diarrhea or diarrhea outcomes with D. fragilis therapy or challenge. Data from seven studies of specific populations reported that 22% had D. fragilis in stools of which only 23% had diarrhea. Eleven studies of stool samples submitted to laboratories reported that 4.3% of individuals had D. fragilis of which 54% had diarrhea. Twelve studies reported that D. fragilis was detected from 1.6% of individuals with diarrhea and 9.6% of diarrheal stools. Five studies analyzed the prevalence of D. fragilis in individuals with and without diarrhea; the two with a statistically significant difference between groups had discordant results. The only cohort study with an appropriate control group reported diarrhea in a higher proportion of children with D. fragilis than in controls. No D. fragilis treatment studies included diarrhea as an outcome. There were only two challenge studies involving one person each. In conclusion, the evidence that D. fragilis would cause diarrhea or that treatment would hasten diarrhea resolution is inconclusive.

Concepts: Statistical significance, Dientamoeba fragilis, Dientamoeba


In this study for the first time, a Dientamoeba fragilis protein profile by MALDI-TOF MS was created in order to identify specific markers for the application of this technology in the laboratory diagnosis of dientamoebiasis. In particular, one D. fragilis reference strain was used to create a reference spectrum and 14 clinical isolates to verify the reliability of the obtained results.

Concepts: Dientamoeba fragilis, Dientamoeba, Trichomonad, Dientamoebiasis


To investigate the prevalence of protozoan contamination by Giardia duodenalis, Cryptosporidium spp., Toxoplasma gondii and Cyclospora cayetanensis, in ‘ready to eat’ (RTE) salads on sale in Italy, 648 packages were purchased from industrial and local brands. Nine individual packages from each brand were collected per month, pooled and subjected to microscopy and molecular analyses. Microscopic examination of 864 slides detected Cryptosporidium spp. but also Blastocystis hominis and Dientamoeba fragilis. Molecular tools identified G. duodenalis assemblage A, Cryptosporidium parvum and Cryptosporidium ubiquitum, T. gondii Type I and C. cayetanensis. B. hominis and D. fragilis were also molecularly confirmed. The overall prevalence of each protozoan species was 0.6% for G. duodenalis, 0.8% for T. gondii, 0.9% for Cryptosporidium spp., and 1.3% for C. cayetanensis, while prevalence for B. hominis was 0.5% and for D. fragilis 0.2%. Microscopy and/or molecular tools revealed that 4.2% of the samples were contaminated by at least one protozoan species, and 0.6% of samples presented contamination by two protozoan species, with a number of oocysts ranging from 62 to 554 per g of vegetable matter for T. gondii, and 46 to 1.580 for C. cayetanensis. This is Europe’s first large-scale study on the presence of protozoans in packaged salads, and shows that RTE sanitation processes do not guarantee a product free from protozoans of fecal origin.

Concepts: Parasites, Apicomplexa, Giardia lamblia, Protozoa, Toxoplasma gondii, Dientamoeba fragilis, Cryptosporidium parvum, Coccidia


Irritable bowel syndrome (IBS) is globally one of the most prevalent gastrointestinal disorders with a negative impact on quality of life and socio-economic status of patients. Recently, controversial evidences suggest that Blastocystis sp. and Dientamoeba fragilis infections may be implicated in the development of IBS. We performed a systematic review and meta-analysis to examine the possible association regarding this issue. PubMed, ScienceDirect, Scopus, Web of Science, and Cochrane electronic databases were searched (up to February 2017) to identify the relevant studies. Pooled odds ratio (OR) and 95% confidence intervals were estimated using a random effects meta-analysis model on data from included studies. A total of 17 studies including 5882 participants (2527 patients and 3310 controls) met the eligibility criteria. Individuals with Blastocystis infection were found to have a positive association with IBS (OR, 2.19; 95% CI, 1.54-3.13), while this association was not observed for D. fragilis infection (OR, 1.13; 95% CI, 0.22-5.72). In subgroup analysis for Blastocystis infection, the pooled ORs were OR 2.29, 95% CI 1.55-3.41; OR 1.70, 95% CI 0.83-3.44; and OR 3.83, 95% CI 2.34-6.27 for hospital-based, healthy volunteers, and combined controls, respectively. Considering the subtypes, meta-analysis result demonstrated significant positive ORs for ST1 (OR, 4.40; 95% CI, 2.81-6.90) and ST3 (OR, 1.94; 95% CI, 1.36-2.77) to be potential risk factors for IBS. Our results support the existence of a positive association between Blastocystis sp. and IBS. Further studies with more sample size should be performed to better investigate the real impact of these parasites on the occurrence of IBS.

Concepts: Epidemiology, Parasites, Medical statistics, Gastroenterology, Irritable bowel syndrome, Dientamoeba fragilis, Dientamoeba


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.

Concepts: DNA, Gene, Genetics, Epidemiology, Disease, Evolution, Biology, Dientamoeba fragilis


The aim of this study was to evaluate the distribution of parasitic intestinal infections in patients attending Padua teaching hospital during a two-year period. Between 1st March 2011 and 28th February 2013, we examined stool specimens from 7341 patients (6127 Italians, 1214 non-Italians) for ova and parasites using microscopy, rapid enzyme immunoassays, culture techniques and molecular methods. Stools of 1080 patients (14.71%) were positive for parasites; a total of 1349 intestinal parasites were counted. Protozoa were detected in 1028/1080 patients (95.19%), while helminths were present in 80/1080 patients (7.41%). The protozoa most commonly detected were Blastocystis spp., Dientamoeba fragilis and Giardia duodenalis. Enterobius vermicularis was the helminth most frequently encountered. Of the 1080 infected patients, 227 (21.02%) had more than one parasite in their stool. To conclude, in Italy intestinal parasitoses must be unquestionably considered in differential diagnoses of gastrointestinal diseases. For this purpose, sound knowledge of epidemiology is essential.

Concepts: Disease, Bacteria, Parasites, Intestinal parasite, Parasitism, Dientamoeba fragilis, Parasitic worm, Pinworm