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.

First detection and molecular characterization of Dientamoeba fragilis in cattle

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.

Should Dientamoeba fragillis be looked for in pediatric digestive pathology of an unknown cause? A proposed pilot case-control study

INTRODUCTION

Dientamoeba (D.) fragilis is a common intestinal protozoan with an unresolved clinical significance. The association between D. fragilis and the etiology of gastrointestinal symptoms in children is unclear. Metronidazole is often used for treatment. The aims of this study are to clarify the clinical relevance of D. fragilis in children with gastrointestinal symptoms, and to determine the clinical and microbiological efficacy of metronidazole in D. fragilis-infected children with gastrointestinal complaints.

METHODS

A prospective case-control study was performed from October 2017 to February 2019. A total of 106 individuals aged 1-17 were included. Out of the 106; 59 showed gastrointestinal symptoms (case group), and 47 were without gastrointestinal symptoms (control group). We excluded 2 patients from the case group. D. fragilis was diagnosed by real-time PCR in stool samples. A 10-day course of oral Metronidazole was prescribed in D. fragilis positive children with GI symptoms. Clinical data before and after the treatment as well as peripheral eosinophilia in previous blood samples, were recorded.

RESULTS

Of the 104 participants, D. fragilis was found in 17 (29.8%) children from the case group, whereas in the control group the parasite was detected in 11 patients (23.4%) with an odds ratio (OR) of 1.39 (IC 95% 0.53-3.75, p=0.46). The most prevalent clinical manifestation was abdominal pain (46/57, 80.7%). Seventeen cases with a positive PCR received anti-parasitic treatment according to the established protocol, although during the collection period we received only 11 stool samples to perform the post-treatment follow-up. The PCR of the D. fragilis remained positive in 3 patients (3/11, 27.27%). Despite achieving the eradication of the parasite, 4/8 patients (50%) continued with digestive symptoms.

CONCLUSIONS

According to our study there were no differences between the D. fragilis infection in children with or without gastrointestinal symptoms. No relation was found between the clinical and microbiological responses after said D. fragilis treatment. Therefore, we conclude that it is not justified to look specifically for D fragilis in pediatric patients with abdominal symptoms.

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, the Neglected Trichomonad of the Human Bowel

Dientamoeba fragilis is a protozoan parasite of the human bowel, commonly reported throughout the world in association with gastrointestinal symptoms. Despite its initial discovery over 100 years ago, arguably, we know less about this peculiar organism than any other pathogenic or potentially pathogenic protozoan that infects humans. The details of its life cycle and mode of transmission are not completely known, and its potential as a human pathogen is debated within the scientific community. Recently, several major advances have been made with respect to this organism's life cycle and molecular biology. While many questions remain unanswered, these and other recent advances have given rise to some intriguing new leads, which will pave the way for future research. This review encompasses a large body of knowledge generated on various aspects of D. fragilis over the last century, together with an update on the most recent developments. This includes an update on the latest diagnostic techniques and treatments, the clinical aspects of dientamoebiasis, the development of an animal model, the description of a D. fragilis cyst stage, and the sequencing of the first D. fragilis transcriptome.

[Dientamoeba fragilis infection as cause of severe abdominal discomfort and flatulence]

The clinical significance of Dientamoeba fragilis infection is controversial. We describe a case-history of a 16-year-old patient, who had suffered severe abdominal discomfort and flatulence through his lifetime. He was eventually diagnosed with D. fragilis infection, and eradication of D. fragilis with high-dose metronidazole kept him without symptoms for one year. Recurrence of the symptoms and recurrence of the D. fragilis infection was thereafter treated successfully with paromomycin.

Investigation of intestinal parasites in dialysis patients

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.

[The importance of being Dientamoeba fragilis]

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.

Detection of Dientamoeba fragilis among diarrheal patients referred to Tabriz health care centers by nested PCR

Dientamoeba fragilis is a protozoan parasite of the human large intestine which is implicated as a cause of gastrointestinal diseases. The diagnosis of this parasite in direct smear preparations is difficult due to the lack of a cyst stage. The permanent staining method is generally used for diagnosis of D. fragilis, but the technique is laborious and time consuming. The purpose of this study was to evaluate the performance of PCR for detection of D. fragilis in clinical specimen of health care center in Tabriz, northwest of Iran. Stool samples of 1000 patients were collected from different laboratories and were immediately examined via wet mount and permanent staining methods. All positive samples and 55 randomly selected negative samples were studied by PCR technique. Using direct smear examination, no positive sample was found among 1000 stool samples, whereas 21 (2.1%) positive and 26 suspicious cases were reported in stained smears. PCR screening indicated that from 21 positive cases, 17 were positive by primary PCR, whereas nested PCR detected all 21 positive cases as well as 3 new positive samples from the suspicious cases (overall 24 (2.4%) positive samples), yet all negative cases remained negative through both stages of PCR amplifications. In comparison with nested PCR (if considered as gold standard), primary PCR showed 81% sensitivity and 100% specificity and those of microscopy was determined to be 87.5% and 100%, respectively. Considering the favorable sensitivity and specificity of nested PCR and its other advantages such as relative simplicity and speed this technique is proposed for rapid diagnosis of D. fragilis in clinical samples.

Blastocystis hominis and Dientamoeba fragilis in patients fulfilling irritable bowel syndrome criteria

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.

[Role of Dientamoeba fragilis in human bowel infections]

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.

Dientamoeba fragilis as a cause of travelers' diarrhea: report of seven cases

Dientamoeba fragilis is a pathogenic trichomonad parasite that causes gastrointestinal disease in humans. We report seven cases of travelers' diarrhea caused by D fragilis in patients who had traveled to overseas destinations within Asia or the Pacific which occurred over an 8-month period. Patients presented with diarrhea lasting from 5 days to over 4 weeks. Dientamoeba fragilis should be considered as a cause of diarrhea in returning travelers.

[Human intestinal parasitosis: role of Dientamoeba fragilis in human infections]

The Authors report prevalences of intestinal parasitosis among home children and adults during 2002-2004, as in O&P as in acute or prolonged diarrhoea, with particular attention to the role of Dientamoeba fragilis, because often undervalued. Among 3139 subjects, 116 cases of dientamoebiasis (3.7%) and 62 of giardiasis (2.0%) were observed; not typical pathogenic protozoa were reported in 71 cases (2.3%); helminths were identified only in 8 cases (0.5%). Particularly, inside O&P group D. fragilis prevailed in 5.2% of cases (7.8% in adults and 0.5% in children) and G. duodenalis in 2.7% (3.5% and 1.3% respectively); inside acute diarrhoeas D. fragilis prevailed in 1.6% (3.9% and 0.3%) and G. duodenalis in 0.6% (1.3% and 0. 1%); inside prolonged diarrhoeas D. fragilis prevailed in 3.5 % (2.6% and 5.4%) and G. duodenalis in 3.9% (5.8% in adults and never in children). D. fragilis was more often observed among adults (6.3% of all) than among children (0.6%), like G. duodenalis (3.1% versus 0.6%). So, 107 strains of D. fragilis (92.2%) and 53 strains of G. duodenalis (85.5%) were identified in adults. D. fragilis was more frequent among females (24/39 cases, 61.5%, in the last year) while G. duodenalis was more frequent in males (13/23 cases, 56.5%). The Authors conclude underlining the importance of a permanent stain, as Giemsa stain, for a good and complete diagnosis of protozoal intestinal infections, particularly for D. fragilis.

Irritable bowel syndrome: a review on the role of intestinal protozoa and the importance of their detection and diagnosis

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder in which abdominal pain is associated with a defect or a change in bowel habits. Gut inflammation is one of the proposed mechanisms of pathogenesis. Recent studies have described a possible role for protozoan parasites, such as Blastocystis hominis and Dientamoeba fragilis, in the etiology of IBS. Dientamoeba fragilis is known to cause IBS-like symptoms and has a propensity to cause chronic infections but its diagnosis relies on microscopy of stained smears, which many laboratories do not perform, thereby leading to the misdiagnosis of dientamoebiasis as IBS. The role of B. hominis as an etiological agent of IBS is inconclusive, due to contradictory reports and the controversial nature of B. hominis as a human pathogen. Although Entamoeba histolytica infections occur predominately in developing regions of the world, clinical diagnosis of amebiasis is often difficult because symptoms of patients with IBS may closely mimic those patients with non-dysenteric amoebic colitis. Clinical manifestations of Giardia intestinalis infection also vary from asymptomatic carriage to acute and chronic diarrhoea with abdominal pain. These IBS-like symptoms can be continuous, intermittent, sporadic or recurrent, sometimes lasting years without correct diagnosis. It is essential that all patients with IBS undergo routine parasitological investigations in order to rule out the presence of protozoan parasites as the causative agents of the clinical signs.

Evaluation of three diagnostic methods, including real-time PCR, for detection of Dientamoeba fragilis in stool specimens

Dientamoeba fragilis is a protozoan parasite of humans that infects the mucosa of the large intestine and is associated with gastrointestinal disease. We developed a 5' nuclease (TaqMan)-based real-time PCR assay, targeting the small subunit rRNA gene, for the detection of D. fragilis in human stool specimens and compared its sensitivity and specificity to conventional PCR and microscopic examination by a traditional modified iron-hematoxylin staining procedure. Real-time PCR exhibited 100% sensitivity and specificity.

Dientamoebiasis: clinical importance and recent advances

Dientamoeba fragilis, an unusual single-celled parasite that was described first in 1918, is found worldwide in the gastrointestinal tract of humans. D. fragilis has emerged from obscurity recently because it is now recognized as a common cause of chronic diarrhoea and is treatable with drugs. Recent molecular studies have described D. fragilis as having two genotypes. Diagnostic tests, based on conventional and real-time PCR, have been developed that will provide a rapid, sensitive and specific diagnosis of D. fragilis. These tests will also aid the elucidation of the host distribution and the life cycle of this pathogen.

Dientamoeba fragilis is more prevalent than Giardia duodenalis in children and adults attending a day care centre in Central Italy

Giardia duodenalis is a well recognised enteropathogen, while Dientamoeba fragilis is rarely detected and consequently it is not recognised as an important human pathogen. In 2002-2003, a survey has been carried out on enteroparasites in faecal samples of outpatients attending a day care centre in the town of Perugia (Central Italy). To improve the detection level, at least three samples from each patient were collected at different days and within two hours from defecation. The coproparasitological examination has been carried out by direct microscopic examination, faecal concentration, and Giemsa and modified Ziehl-Nielsen stainings of faecal smears. The genotypes of Giardia duodenalis isolates were determined by PCR of the beta-giardin gene. Of 1,989 enrolled people (966 children, 1,023 adults), 165 persons (8.3%; 153 adults, 15.0%; 12 children, 1.2%), were positive for parasites, but only 1 12 adults (73.2% of those infected) and eight children (66.7% of those infected) harboured D. fragilis and G. duodenalis. Both the Assemblages A and B were detected in 18 G. duodenalis isolates examined at the beta-giardin gene. The higher prevalence of D. fragilis infections than that of G. duodenalis is probably related to the method used, a procedure, which is rarely followed in laboratories for the diagnosis of enteric parasites. These epidemiological data suggest that when faecal samples are examined after a period of time and without Giemsa staining, most D. fragilis infections goes undetected.

Detection of Dientamoeba fragilis in fresh stool specimens using PCR

Dientamoeba fragilis is a trichomonad parasite that causes human gastrointestinal disease. Currently microscopy is considered to be the gold standard for diagnosis of D. fragilis infection. However, this method is time-consuming and relatively insensitive. A PCR assay based on the small-subunit ribosomal RNA gene of D. fragilis for the specific detection of D. fragilis DNA in fresh unpreserved stool samples was developed. The D. fragilis PCR was positive in 29/31 samples with positive microscopy and did not cross-react with other protozoan parasites. The PCR protocol showed a specificity of 100% and a sensitivity of 93.5% and the entire procedure can be performed in one day.

Emerging from obscurity: biological, clinical, and diagnostic aspects of Dientamoeba fragilis

Ever since its first description in 1918, Dientamoeba fragilis has struggled to gain recognition as a significant pathogen. There is little justification for this neglect, however, since there exists a growing body of case reports from numerous countries around the world that have linked this protozoal parasite to clinical manifestations such as diarrhea, abdominal pain, flatulence, and anorexia. A number of studies have even incriminated D. fragilis as a cause of irritable bowel syndrome, allergic colitis, and diarrhea in human immunodeficiency virus patients. Although D. fragilis is most commonly identified using permanently stained fecal smears, recent advances in culturing techniques are simplifying as well as improving the ability of investigators to detect this organism. However, there are limitations in the use of cultures since they cannot be performed on fecal samples that have been fixed. Significant progress has been made in the biological classification of this organism, which originally was described as an ameba. Analyses of small-subunit rRNA gene sequences have clearly demonstrated its close relationship to Histomonas, and it is now known to be a trichomonad. How the organism is transmitted remains a mystery, although there is some evidence that D. fragilis might be transmitted via the ova of the pinworm, Enterobius vermicularis. Also, it remains to be answered whether the two distinct genotypes of D. fragilis recently identified represent organisms with differing virulence.

[Dientamoeba fragilis: possibly an important cause of persistent abdominal pain in children]

OBJECTIVE

To determine the effect of an antiprotozoic treatment on children with persistent abdominal pain and infection with Dientamoeba fragilis.

DESIGN

Retrospective.

METHOD

A total of 43 children with D. fragilis infection and persistent gastrointestinal complaints were included in the study. Of these 27 were treated with clioquinol and 16 with a nitroimidazole drug: metronidazole or tinidazole. The parasitological and clinical effects of the treatment were assessed.

RESULTS

In 33 of the 43 (77%) children, no parasites were detected during follow-up with a triple faeces test: 22/27 following treatment with clioquinol and 11/16 following treatment with a nitroimidazole drug. In 27 of the 33 (82%) children with a negative follow-up result, gastrointestinal complaints were considerably less or had completely disappeared. In 2 of the 10 (20%) children in which D. fragilis had not disappeared in the follow-up period, the complaints were less or had disappeared.

CONCLUSION

Effective treatment of D. fragilis infection in children with longstanding gastrointestinal complaints often resulted in a reduction or disappearance of the complaints.

Direct amplification and genotyping of Dientamoeba fragilis from human stool specimens

Dientamoeba fragilis is a globally occurring parasite that has been recognized as a causative agent of gastrointestinal symptoms. A single-round PCR was developed to detect D. fragilis DNA directly from human stool samples. The genetic diversity of D. fragilis from 93 patients and 6 asymptomatic carriers was examined by PCR followed by restriction fragment length polymorphism and sequencing of part of the small-subunit rRNA gene. The data show that D. fragilis sequences can be studied directly from fecal specimens despite the absence of a cyst stage and without the need for prior culturing. In addition, the results suggest strongly that D. fragilis shows remarkably little variation in its small-subunit rRNA gene.

Detection of Dientamoeba fragilis by culture

Symptoms associated with Dientamoeba fragilis include diarrhoea, abdominal pain, nausea, vomiting, epigastric pain and weight loss. A possible link between D. fragilis and irritable bowel syndrome (IBS)-like symptoms has been reported, and therefore the presence of this parasite should be excluded before making a diagnosis of IBS. Over a six-month period, 976 faecal samples were submitted to NPHS Microbiology Aberystwyth for routine microbiological analysis. All samples were also cultured for parasites using Robinson's xenic medium. Trichrome staining was undertaken whenever practicable, but many stools had insufficient material. D. fragilis was isolated from 25 (2.6%) patients, whereas Cryptosporidium spp. was detected in 16 (1.6%) patients. D. fragilis was only detected in nine (1.3%) out of 685 specimens stained with trichrome, although four of the 25 culture-positive stools had insufficient sample for staining. Parasite culture proved to be less laborious than trichrome staining and dramatically increased D. fragilis detection rate.

Dientamoeba fragilis infection presenting to the emergency department as acute appendicitis

Dientamoeba fragilis is a non-enteroinvasive, protozoan parasite of the human large intestine with a worldwide prevalence. Considered for years to be a non-pathogenic organism, more recent studies suggest that up to 25% of adult hosts and up to 90% of infested children may manifest clinical disease. D. fragilis infestation has been implicated in chronic gastrointestinal syndromes characterized by protean complaints such as post-prandial abdominal pain, chronic diarrhea, flatulence, fatigue, anorexia, and weight loss. Rarely, D. fragilis infestation is the etiology of acute abdominal pain, mimicking a surgical abdomen. A case report is presented that details a patient with a 1-month history of vague abdominal complaints who presented to the Emergency Department with an apparent episode of acute appendicitis.

[Dientamoeba fragilis: is it really fragile? Approach to specimen handling and rapid microscopic diagnosis]

Dientamoeba fragilis is a pathogenic protozoan parasite with a world-wide distribution. Interestingly, a resistant cyst stage has not been demonstrated and it is still an unsolved problem how this parasite can survive successfully outside the human host. D. fragilis was found in 2% of approximately 2500 individuals unselected who submitted stools for parasitological examination during 2001 in Padua (Italy). The goal of this study was to detect the protozoan stages and the duration of persistence of this protozoa in faeces stored in different environmental conditions. The trophozoites of D. fragilis were detected up to 60 days after the collection of the faeces stored at 4 degrees C and Giemsa stained. The laboratory detection rate of the organism is greatly enhanced by use of preservative to fix stool specimens immediately after passage. Alternatively, a microscopic observation of the collected stool has to be performed immediately after passage followed by examination of permanently-stained smears. Demonstration of the charateristic "golf-club" and "acanthopodia-like" structures in unstained fixed faecal material by direct microscopy (400x) are suitable for a rapid identification of D. fragilis.

[Dientamoeba fragilis and dientamoebiasis: aspects of clinical parasitology and laboratory diagnosis]

The flagellate Dientamoeba fragilis is a potential intestinal pathogen of humans. It is probably undervalued overall because its identification relies on permanent stains directly on fresh fecal specimens (Giemsa) or preserved in PVA or SAF (Trichrome or Iron-hematoxylin). During 1999 we processed stoll samples of 151 subjects and we searched also D. fragilis. We processed 105 cases of enteritis (82 children and 23 adults) and 46 samples of formed stools to investigate only for intestinal parasites (12 children and 34 adults). The microscopical observations were made on smears directly in saline solution, and after Dobell solution, MIF and Giemsa stained. Iron hematoxylin and trichrome stains were performed in some circumstances only. D. fragilis was observed in 11.3% of cases, 7.6% among the group of enteritis and 13.8% among the other subjects. These positive 17 cases were observed more often among adults (76.5% of cases) than among children (23.5%). In our study area D. fragilis seems more frequent than Giardia intestinalis and represents the third important intestinal parasite, following Enterobius vermicularis (children) and Strongyloides stercoralis (elders).

[Dientamoeba fragilis--an old parasite sparks new interest]

Dientamoeba fragilis is a protozoan parasite of the human colon with only the trophozoite stage identified. The exact mode of transmission is still unknown. Formerly considered to be apathogenic, several studies have suggested that D. fragilis has pathogenic properties. Common symptoms of the infection include diarrhea and abdominal pain. After reviewing the literature we suggest that treatment can be considered for patients with prolonged symptoms, provided no other causative agent has been found.

Dientamoeba fragilis: the unflagellated human flagellate

Dientamoeba fragilis is a pathogenic protozoan parasite with a world-wide distribution. Although originally described as an amoeboid organism, it has been reclassified as a flagellate, on the basis of a number of electron microscopic and immunological findings. Except for its lack of a flagellum, D. fragilis closely resembles Histomonas and Trichomonas. Interestingly, a resistant cyst stage has not been demonstrated and it is unlikely that its trophozoites can survive successfully outside the human host. As a consequence of its higher than anticipated coincidence of infection with Enterobius vermicularis, transmission may occur via ova of this pinworm. D. fragilis infection may be acute or chronic, and has been reported in both children and adults. The most common clinical symptoms include abdominal pain, persistent diarrhoea, loss of appetite, weight loss and flatulence. Occasionally, eosinophilia, urticaria and pruritus have been described. Demonstration of the characteristic nuclear structure of D. fragilis, needed for a definitive diagnosis, cannot be achieved in unstained faecal material; therefore, permanently stained smears are essential. Treatment is recommended in symptomatic cases, and iodoquinol, tetracycline and metronidazole have been used successfully.

[Dientamoeba fragilis: pathogenic flagellate?]

INTRODUCTION

D. fragilis is an intestinal protozoa whose pathogenic characteristics are increasingly recognized. The aim of this study is to specify the epidemiologic, biological and clinical aspects of this protozoa. MATERIAL USED AND METHODOLOGY: Survey conducted on 27,058 parasitological test of stools in parasitology-mycology laboratory of the Sfax University Hospital over a period of 5 years.

RESULTS

11,254 parasitological test of stools were positive (41.6%) of which 89.3% comprised protozoa. D. fragilis was found in 1497 cases (13.3% of the positive cases). In 65% of these cases, it was associated with other intestinal parasites in particular Blastocystis hominis (40.3%), Endolimax nanus (24%), Entamoeba coli (6%), Giardia intestinalis (5.7%) and Enterobius vermicularis (5%). Those patients having a parasitism with isolated D. fragilis were predominantly female and young subjects (< 20 years). Clinical signs included abdominal pain (88.5%), anorexia (50%), alternating diarrhoea and constipation (40.4%) and diarrhoea (21%) with mucus in 7.6%.

DISCUSSION

D. fragilis is today classified in the group of flagellates and we share the opinion of the majority of the authors as to its real pathogenic capacity.

Dientamoeba fragilis masquerading as allergic colitis

BACKGROUND

Dientamoeba fragilis is a rare cause of chronic infectious diarrhea and colitis in children.

METHODS

Review of the clinical manifestations, diagnostic methods, and clinical course of D. fragilis infection in our hospital.

RESULTS

Eleven pediatric patients are discussed, seven of whom had a history of recent travel. Clinical manifestations of infectious diarrhea included anorexia, intermittent vomiting, abdominal pain, and diarrhea, ranging from 1 to 100 weeks in duration. Peripheral eosinophilia was present in seven patients. One patient with well-documented bovine protein allergy had intermittent episodes of diarrhea and abdominal pain, despite an appropriate elimination diet. Eosinophilic colitis documented by colonoscopy, was due to D. fragilis. Metronidazole was effective in treating five patients, and iodoquinol was effective in treating four others.

CONCLUSIONS

D. fragilis should be included in the differential diagnosis of chronic diarrhea and eosinophilic colitis. The identification of this pathogen requires clinical awareness of epidemiologic risk factors and presenting complaints, as well as the laboratory staining procedures essential to its proper identification.

Enteropathogens associated with diarrhea among military personnel during Operation Bright Star 96, in Alexandria, Egypt

This study investigated the microbial causes of diarrheal disease among U.S. troops deployed near Alexandria, Egypt, during October 1995. Bacterial causes associated with 19 cases of diarrhea included: enterotoxigenic Escherichia coli (ETEC), 42% (21% heat-stable, 11% heat-labile, and 11% heat-stable/ heat-labile producers); enteropathogenic E. coli (5.3%); and enteroadherent E. coli (42%). Four cases of diarrhea were associated with enteroaggregative E. coli based on probe analysis for enteroaggregative heat-stable enterotoxin 1. Protozoan causes included; Entamoeba histolytica (11%), E. hartmanni (5%), E. nana (5%), Blastocystis hominis (5%), Chilomastix mesnili (11%), Dientamoeba fragilis (5%), Entamoeba coli (5%), and Cryptosporidium (5%). Shigella, Aeromonas, Plesiomonas, Vibrio, Campylobacter, and Salmonella were not detected. Of the eight ETEC cases, one was colonization factor antigen (CFA)/I only, one was both CFA/I and CFA/III, three were CFA/II, two were CFA/IV, and two were CFA-negative. Antibiograms of the ETEC and enteroadherent E. coli strains showed that all isolates were susceptible to norfloxacin, ciprofloxacin, and nalidixic acid but resistant to ampicillin, tetracycline, chloramphenicol, and sulfamethoxazole.

Prevalence of Dientamoeba fragilis antibodies in children and recognition of a 39 kDa immunodominant protein antigen of the organism

Dientamoeba fragilis, a common intestinal protozoan parasite in Canada, has been associated with diarrhoea and abdominal pain in some patients. Seroprevalence of this organism has not been reported previously. In the present study sera from three symptomatic patients, 12 age- and sex-matched controls, and 189 randomly selected healthy individuals (age 6 months to 19 years) were tested for antibodies against Dientamoeba fragilis by an indirect immunofluorescence (IIF) assay. All three symptomatic patients infected with Dientamoeba fragilis had positive IIF titres of 80, and all 12 matched controls had positive titres ranging 20 to 160 (geometric mean titre 48). Of the 189 healthy children, 172 (91%) were positive at a serum dilution of 1:10 or higher. The specificity of the IIF assay was reinforced by immunoblotting 20 representative serum samples against Dientamoeba fragilis. In all 17 IIF-positive serum samples, a 39 kDa protein band of Dientamoeba fragilis was identified, the same band recognized by a mouse monoclonal antibody raised in our laboratory. Findings over a five-year period indicate that Dientamoeba fra-gilis was the most common protozoan, followed closely by Giardia lamblia and more distantly by Cryptosporidium parvum. The high seropositivity of 91% for Dientamoeba fragilis compares reasonably well with serologic data obtained by IIF and reported previously for Giardia lamblia (85.6%) and Cryptosporidium parvum (86%).

How many stool examinations are necessary to detect pathogenic intestinal protozoa?

Recent reports have suggested that examination of one stool specimen is sufficient to detect protozoa in symptomatic patients. To verify this hypothesis, we examined specimens submitted to the regional laboratory of a large, prepaid health plan that provides primary care to a membership representative of the general population in northern California. We examined the number and results of stool specimen examinations in the two-month period before detection of Entamoeba histolytica in 125 infected persons, of Giardia lamblia in 154 infected persons, and of Dientamoeba fragilis in 60 persons infected with this parasite. About 13% of the entire group had a single stool specimen examined, 19% had two examined, 65% had three examined, and 6% had more than three examined. Most infections were detected in the first specimen or specimens submitted, but many were not detected until later examination. Thirteen patients with E. histolytica (10.4%) required 4-9 examinations. The sensitivity of one examination was compared with that of three examinations; with the additional examinations, the yield increased 22.7% (95% confidence interval [CI] = 11.8-33.5%) for E. histolytica, 11.3% (95% CI = 6.9-81.8%) for G. lamblia, and 31.1% (95% CI = 17.7-54.4%) for D. fragilis. Our results suggest that a single stool specimen examination will miss many pathogenic protozoan infections in symptomatic persons.

Application of indirect immunofluorescence to detection of Dientamoeba fragilis trophozoites in fecal specimens

An indirect fluorescent-antibody (IFA) assay was carried out to examine for the presence of Dientamoeba fragilis trophozoites in preserved fecal specimens. Antiserum to D. fragilis trophozoites was raised in a rabbit with a dixenic culture of D. fragilis (ATCC 30948) from the American Type Culture Collection. After absorption with Klebsiella pneumoniae and Bacteroides vulgatus, the immune rabbit serum was used for examination by the IFA assay. A total of 155 clinical samples were tested; 42 with no parasites, 9 with D. fragilis, and 104 with other parasites. The IFA assay identified seven D. fragilis organisms. Two specimens with doubtful IFA assay readings showed very scanty amounts of D. fragilis trophozoites on stained smears. There were no false-positive IFA assay readings. The IFA assay appeared to be a promising method because of its speed in screening. The specificity of the IFA assay indicates that other diagnostic tests such as an enzyme-linked immunosorbent assay could be developed to identify D. fragilis antigens in fecal specimens.

Diagnosis by faecal culture of Dientamoeba fragilis infections in Australian patients with diarrhoea

This paper reports the first survey in Australia to use faecal culture to detect Dientamoeba fragilis in patients with diarrhoea. Of 3 different protozoal culture media evaluated on a case of known infection, modified Boeck & Drbohlav's medium was the most suitable. The organism could be grown from faeces stored for up to 24 h at room temperature, but for only 10 h at 4 degrees C. Culture was then used, in combination with microscopy of smears fixed with polyvinyl alcohol and trichrome-stained, to examine single stool specimens from 260 consecutive patients with diarrhoea in the city of Brisbane. D. fragilis was detected in 4 (1.5%) specimens, only 2 of which were positive by microscopy. Other protozoa were found in 36 (13.8%) specimens: Blastocystis hominis in 28 (10.8%), Giardia duodenalis in 4 (1.5%), Endolimax nana in 3 (1.2%), and Entamoeba coli in one (0.4%). One strain of Dientamoeba was cryopreserved in liquid nitrogen and recultured successfully 10 d later. Culture was more sensitive than microscopy in diagnosing D. fragilis infection and the organism, of dubious pathogenicity, was not common in patients with diarrhoea in this community. Prevalence surveys of intestinal protozoan infections should use faecal culture, and specimens should be less than 12 h old and not refrigerated. Dientamoeba strains isolated by culture can be cryopreserved.

Dientamoeba fragilis infection, a cause of gastrointestinal symptoms in childhood

Clinical and laboratory findings of 123 paediatric patients with infections due to intestinal protozoa were analysed. Dientamoeba fragilis (D.f.) was found in 102 cases. The other patients had infections with Giardia lamblia or mixed infections with several other protozoa. Acute and recurrent diarrhoea were the most common findings (56 cases), whereas abdominal pain was more common in children with chronic symptoms. Peripheral eosinophilia was present in 32% of the children with dientamoebiasis. Metronidazole, oxytetracycline, doxycycline, and erythromycin were the most effective drugs in the treatment of D.f. infections. The therapy led coincidentally to the sanitation of stools and elimination of abdominal complaints. The investigations underline the pathogenic role of D.f. in those children with gastrointestinal symptoms. Mixed infections of D.f. and Enterobius vermicularis suggest a vector bound transmission of D.f.

Dientamoeba fragilis: a bowel pathogen?

Although many patients infected with Dientamoeba fragilis suffer gastrointestinal symptoms, controversy still surrounds the pathogenic role of this intestinal protozoan. We describe three patients infected with D fragilis who had gastrointestinal symptoms. In the first patient symptoms resolved with therapy before the protozoan was eradicated from the stool, however in the second, symptoms persisted unabated despite clearing of the organism. In the third patient, symptoms resolution was associated with effective treatment. We discuss the life cycle, diagnosis and treatment of this organism and its role as a pathogen.

Colitis due to Dientamoeba fragilis

Clinical reports have suggested that the parasite Dientamoeba fragilis may be a cause of acute and chronic colitis in children and adults. The mechanism by which this parasite produces colitis has not been determined. The clinical findings in this case report suggest that D. fragilis causes colitis through an invasive ulcerating process.

Dientamoeba fragilis: a gastrointestinal protozoan infection in adults

Dientamoeba fragilis is a protozoan parasite of the large intestine of man. Individuals with infection may be asymptomatic or have gastrointestinal and systemic symptoms. We report a patient with symptomatic D. fragilis infection and negative extensive laboratory and radiological workup, with resolution of symptoms after diiodohydroxyquin therapy. No parasites were detected in three follow-up stool examinations. We then undertook retrospective study to define and describe further clinical symptoms in adults with this infection by analysis of data from medical records of 50 subjects with this parasite.

Dientamoeba fragilis. An intestinal pathogen in children?

A retrospective study was conducted of 35 children in whom Dientamoeba fragilis was the only parasite found in the gastrointestinal (GI) tract. Gastrointestinal symptoms were present in 32 (91%) of these children; diarrhea was the most common finding in patients with acute symptoms, whereas abdominal pain was more common in children with chronic symptoms. Peripheral eosinophilia was present in half of the children examined and was statistically more significant in patients with D fragilis than in a control group of children admitted for elective surgery. Therapy with diiodohydroxyquin or metronidazole was effective; children's symptoms were diminished or were eliminated on follow-up evaluation after treatment. From this association between therapy and symptomatic relief, D fragilis should be considered pathogenic in those children with GI symptoms.