Detection of Blastocystis sp. and Dientamoeba fragilis using conventional and molecular methods in patients with celiac disease

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.

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

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

Detection and genotyping of Dientamoeba fragilis from symptomatic patients: New insights from Italy into a little-known gastrointestinal protozoan

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.

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.

Intestinal Microbiota in Children With Symptomatic Dientamoeba fragilis Infection: A Case-control Study

BACKGROUND

Dientamoeba fragilis in children has been associated with gastrointestinal symptoms, like abdominal pain and diarrhea. The mechanism underlying these symptoms in children with D. fragilis remains unclear. We hypothesized that concomitant microbial alterations, which have been described in other parasitic infections, may be associated with gastrointestinal symptoms in D. fragilis.

METHODS

In this case-control study performed in 2 centers, 19 children referred to a pediatrician because of gastrointestinal symptoms and with a positive fecal PCR for D. fragilis were included as cases. We included 19 healthy children as controls and matched for age and gender, selected from an existing cohort of 63 children. A PCR for D. fragilis was performed on fecal samples of the 19 controls to assess D. fragilis carriership in this asymptomatic group. Microbiota was analyzed with the IS-pro technique, and the intestinal microbiota composition and diversity were compared between the 2 groups.

RESULTS

Microbiota of children with D. fragilis and gastrointestinal symptoms did not significantly differ in terms of composition and diversity compared with controls, both on phylum and species level. In the asymptomatic controls, a positive fecal PCR for D. fragilis was found in 16 of 19 (84.2%).

CONCLUSION

Intestinal microbiota does not seem to play a key role in the presence of clinical symptoms in children with D. fragilis. The pathogenicity of D. fragilis and pathophysiologic pathways underlying the development of gastrointestinal symptoms remains yet to be clarified.

Blastocystis prevalence and subtypes in autochthonous and immigrant patients in a referral centre for parasitic infections in Italy

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.

Is the treatment of Enterobius vermicularis co-infection necessary to eradicate Dientamoeba fragilis infection?

OBJECTIVES

Dientamoeba fragilis is a pathogenic protozoan of the human gastrointestinal tract with a worldwide distribution, which has emerged as an important and misdiagnosed cause of chronic gastrointestinal illnesses such as diarrhea and 'irritable-bowel-like' gastrointestinal disease. Very little research has been conducted on the use of suitable antimicrobial compounds. Furthermore, higher rates of co-infection with Enterobius vermicularis have been described, suggesting that E. vermicularis could influence the treatment of D. fragilis-infected patients. To study this, the treatment of E. vermicularis and D. fragilis co-infected patients was evaluated.

METHODS

Forty-nine patients with a D. fragilis infection, including 25 (51.0%) patients co-infected with E. vermicularis, were studied. All of them were treated with metronidazole. Patients with E. vermicularis co-infection and/or an E. vermicularis-positive case in the family were treated with mebendazole.

RESULTS

Metronidazole treatment failure was significantly more frequent in patients with E. vermicularis co-infection and in patients with children in the family.

CONCLUSIONS

Co-infection with E. vermicularis may act as a factor favoring D. fragilis infection by preventing eradication measures. This suggests that both parasites should be treated simultaneously.

PREVALENCE OF DIENTAMOEBA FRAGILIS AMONG AN ORANG ASLI POPULATION IN RURAL MALAYSIA

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.

[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.

Prevalence and clinical features of Dientamoeba fragilis infections in patients suspected to have intestinal parasitic infection

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).

[Intestinal infections caused by Dientamoeba fragilis and Giardia duodenalis in our experience]

Between 2002 and 2003 the Authors analyzed stool specimens of 1,989 subjects, 966 children (1-14 years old) and 1,023 adults, to investigate for intestinal protozoa too: 380 children and 656 adults with intestinal aspecific troubles, 546 children and 291 adults with acute diarrhoea, 40 children and 76 adults with prolonged diarrhoea. G. duodenalis prevailed in 1.8% of all cases (0.2% among children and 3.2% among adults), D. fragilis in 4.1% (0.6% and 7.3% respectively). Other pathogenic parasites were very rare. Only B. hominis (opportunistic/saprophytic protozoon) or other commensal protozoa were observed, also associated with D. fragilis and/or G. duodenalis. Among subjects suffering from intestinal aspecific troubles, G. duodenalis prevailed in 3.7% and D. fragilis in 8.7% of adults; both protozoa were observed in 0.5% of children each one. Among acute diarrhoeas G. duodenalis was observed in 1.7% of adults and never in children, D. fragilis in 4.5% and 0.4% respectively. Among prolonged diarrhoeas, G. duodenalis was observed in 5.3% of adults and never in children, D. fragilis in 6.6% of adults an in 5.0% of children. The Authors emphatyze the clinical importance of D. fragilis and the diagnostical importance of a permanent stain, like Giemsa, for a good and sure diagnosis.

[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.

[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.

Clinical and microbiological features of dientamoebiasis in patients suspected of suffering from a parasitic gastrointestinal illness: a comparison of Dientamoeba fragilis and Giardia lamblia infections

OBJECTIVES

To describe the clinical and microbiological features of Dientamoeba fragilis and Giardia lamblia infected patients, and to analyze the genetic variation of D. fragilis strains.

METHODS

For a period of two years, all stool samples collected from patients suspected of having a parasitic gastrointestinal infection were examined according to our specific triple feces test (TFT) protocol. A retrospective case-control study was performed on D. fragilis and G. lamblia infected patients. Furthermore, PCR and genotyping by restriction fragment length polymorphism (RFLP) were performed upon the former.

RESULTS

D. fragilis (6.3%) and G. lamblia (7.1%) were the most common pathogenic protozoa isolated out of 448 patients studied. Symptoms most frequently encountered with D. fragilis and G. lamblia infection were abdominal pain (69.2% and 72.4%, respectively) and diarrhea (61.5% and 79.3%, respectively). However, patients with D. fragilis infections suffered significantly less frequently from nausea and/or vomiting, anorexia and weight loss. After treatment, all D. fragilis and G. lamblia infected patients presenting a negative TFT follow-up also reported a complete resolution of their symptoms. Only genotype 1 could be detected in D. fragilis infected patients.

CONCLUSIONS

D. fragilis and G. lamblia were the most frequently encountered parasites in our study population. Improved diagnostic tests are essential tools to study the prevalence and pathogenesis of D. fragilis.

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.

Prospective study of the prevalence, genotyping, and clinical relevance of Dientamoeba fragilis infections in an Australian population

A prospective study was conducted over a 30-month period, in which fecal specimens from 6,750 patients were submitted to the Department of Microbiology at St. Vincent's Hospital, Sydney, Australia. Trophozoites of Dientamoeba fragilis were detected in 60 (0.9%) patients by permanent staining, and confirmation was performed by PCR. Gastrointestinal symptoms were present in all patients, with diarrhea and abdominal pain the most common symptoms. Thirty-two percent of patients presented with chronic symptoms. The average age of infected patients was 39.8 years. No correlation was found between D. fragilis and Enterobius vermicularis, a proposed vector of transmission for D. fragilis. The genetic diversity of 50 D. fragilis isolates was examined by PCR, and the PCR products were analyzed for the presence of restriction fragment length polymorphisms. These results showed no variation in the small-subunit rRNA gene and demonstrated a single genotype for all Australian isolates. This study shows the potential pathogenic properties of D. fragilis and the need for all laboratories to routinely test for this organism.

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 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--a protozoal infection which may cause severe bowel distress

A retrospective study of 87 patients diagnosed with the protozoan Dientamoeba fragilis was performed due to a recent increase in the number of patients diagnosed with this organism at the Unit of Clinical Parasitology, Huddinge University Hospital, Stockholm, Sweden. Medical records were reviewed. The highest incidence was found in pre-school boys, who also had the longest duration of symptoms, with a range of 1-630 weeks. A majority of the patients had symptoms of diarrhea, abdominal pain and flatus. The diarrhea varied from watery to loose, blood being reported only sporadically. Most patients had traveled outside Europe and had no other parasites in their stools. This study indicates potential pathologic properties in D. fragilis, and prospective studies are recommended.

[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 unusual intestinal pathogen

This is a case report of a gastrointestinal infection caused by Dientamoeba fragilis. It is a flagellate protozoan that is an uncommon etiology of gastrointestinal disease. Primarily characterized by diarrhea and abdominal pain, other symptoms such as flatulence, nausea, vomiting, fatigue, malaise, and weight loss occur. Diagnosis is made using multiple fresh stool samples that are preserved and permanently stained looking for the typical binucleate trophozoite. Since there is a distinct association with Enterobius vermicularis (possibly the mode of protozoan transmission), the human pinworm is also sought. Treatment of choice consists of diiodohydroxyquin in adults and metronidazole in children.

Descriptive features of Dientamoeba fragilis infections

A total of 237 cases of Dientamoeba fragilis were identified by a state public health laboratory in 1985 and 1986. Dientamoeba fragilis was the only parasite found in about two-thirds of the cases. Compared to Giardia cases diagnosed in a similar time period, D. fragilis occurred more frequently in females and in children 5-9 years old; it was also more likely to be detected in spring and summer months. Giardia occurred more frequently in children 0-4 years old. Seventy-nine per cent of 70 interviewed D. fragilis cases reported symptoms associated with infection; nearly 80% had diarrhoea or loose stools. Interviewed cases reported more household and non-household exposure to children 5-9 years old than children of other ages. The difference in age and sex distribution of D. fragilis and Giardia cases may be related to the life cycle and mode of transmission of the two protozoans.

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.

Dientamoeba fragilis, a protozoan parasite in adult members of a semicommunal group

Dientamoeba fragilis is an intestinal protozoan parasite associated with gastrointestinal symptoms. This study was undertaken in a semicommunal group reported to have a high prevalence of this parasite. Stools were collected from 81 adult group members. Intestinal parasites were observed in stool specimens of 45 (56%) of the 81 adults; D. fragilis was found in 33 (41%) subjects. This paper describes the clinical findings and treatment of 26 adults with D. fragilis alone or with a commensal. Gastrointestinal symptoms were observed in 22 (85%) of infected subjects; abdominal pain and excessive flatus were significantly more common in this group. diiohydroxyquin 650 mg three times a day for 20 days eliminated the parasite in 10 (83%) of the 12 treated, although three subjects required a second course of therapy. Parasitic infection should be considered in patients with vague gastrointestinal symptoms, especially those living in endemic areas, in close proximity, or with a history of foreign travel.

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.

Comparison of immediate polyvinyl alcohol (PVA) fixation with delayed Schaudinn's fixation for the demonstration of protozoa in stool specimens

Immediate fixation of stool specimens in polyvinyl alcohol fixative (PVA) was compared with Schaudinn's fixation delayed until the specimens were received in the laboratory, in a series of 100 consecutive positive stool specimens. More specimens were found positive following PVA fixation, and the numbers of organisms present on the slides were greater in specimens processed by this technique than after Schaudinn's fixation. It is concluded that immediate fixation results in the preservation of larger numbers of organisms in a recognizable state. The routine use of PVA fixation prior to transportation of the specimen to the laboratory is recommended.

Dientamoeba fragilis: a review with notes on its epidemiology, pathogenicity, mode of transmission, and diagnosis

Dientamoeba fragilis was found in 4.2% of approximately 43,000 individuals who submitted stools for parasitological examination during 1970 to 1974. The parasite was more frequently found in the younger age group (less than 20 years) than in older age groups, and more often in females than in males. Symptoms in 255 of patients in whom D. fragilis was the only parasite found and for whom detailed symptoms had been supplied, included: diarrhea, abdominal pains, anal pruritus, and loose stools. Analysis of mixed infections of D. fragilis with intestinal helminths suggests that such infections are random except for the combination of D. fragilis and Enterobius vermicularis. This combination occurred 9 times more often than theoretically expected. Daily periodicity and distribution of D. fragilis within stools of one patient were studied over a period of 6 months. More than twice as many organisms per ml of stool were present in the last than in the first portion evacuated. The total number of organisms excreted fluctuated markedly from day to day.