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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.

Adolescent↗

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.

Adolescent↗

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.

Abdominal Pain↗

Parasitic infections in a pediatric population.

We studied the frequency of parasitic infection and associated clinical symptoms in children who attended general pediatric and dental clinics at UCLA. Parasites were detected in stool specimens of 40 (38%) of the 1-4 children completing the study. Protozoan parasites were recovered in 39 (38%); one child had whipworm eggs. Parasites included Dientamoeba fragilis in 22 (21%) children and Giardia lamblia in 18 (17%) children; commensals were observed in 15 (14%) children. Parasitic infection was more frequent in younger children, those with a history of immigration or foreign travel and those attending a day care center. A significant proportion of children with parasites had vague gastrointestinal complaints; however, parasites had not been considered as the etiologic agent by the parent or child's physician. Anorexia, irritability and gas were frequent in children with G. lamblia; abdominal pain was more frequent in those with D fragilis. Intestinal parasitic infection should be considered in children with vague gastrointestional complaints, particularly those in endemic areas, with a history of foreign travel or immigration or attending a day care center. Siblings of infected children should have stool examination even if asymptomatic.

Adolescent↗

Treatment of Dientamoeba fragilis infection with paromomycin.

Treatment with paromomycin (25-35 mg/kg/d for 7 days) was evaluated prospectively in 15 children with Dientamoeba fragilis infection after 1-month follow-up. At the end of the study, parasitologic effectiveness and clinical improvement were observed in 12/15 (80%) and 13/15 (87%) patients, respectively. Paromomycin appears to be an effective drug for treatment of D. fragilis infection in children.

Adolescent↗

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.

Adult↗

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.

Animals↗

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.

Animals↗

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.

Abdominal Pain↗

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.

Animals↗

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.

Amebiasis↗

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.

Adolescent↗

Intestinal protozoan infection in a semicommunal group.

A survey was conducted to determine the prevalence of protozoan parasites in a large semicommunal group in Los Angeles. Protozoan parasites were observed in 151 (69%) of the 220 group members in the study. Parasites were observed in stool specimens from 105 (76%) of the 138 children and 46 (56%) of the 82 adults. Dientamoeba fragilis was observed in 115 (52%), Giardia lamblia in 50 (23%), Entamoeba histolytica in 9 (4%), and commensals in 61 (28%). Parasitic infection was infrequent in infants less than 1 year old, was demonstrated in 33 (89%) of the 2- to 4-year-olds, 69 (78%) of the 89 school age children 8-15 years of age, and in 46 (56%) of the 82 adults. G. lamblia was most prevalent in children younger than 6 years; whereas D. fragilis was common in all age groups. The fecal-oral route was the most likely means for parasite transmission. Since the group at times serves meals to the public, spread of parasites outside the community is a potential public health problems. Diagnosis of parasitic infection is dependent on optimal stool collection, proper laboratory techniques and trained personnel.

Adolescent↗

Intestinal protozoa in homosexual men of the San Francisco Bay area: prevalence and correlates of infection.

To compare the prevalence of intestinal parasitic infection in male homosexuals selected from other sources with the levels previously reported from clinic-derived populations, various homosexual groups of the San Francisco Bay Area were checked by means of stool examination and questionnaires for prevalence of intestinal parasites and for related sexual behavioral patterns during a 3-year period. The prevalence of Entamoeba histolytica (28.6%) was similar to that reported in other studies, whereas that of Giardia lamblia was lower. Infection with E. histolytica was correlated significantly with a prior history of syphilis or gonorrhea (P less than 0.0001), with the number of sexual partners in the preceding 12-month period (P less than 0.0001), and with the reported frequency of oral-anal sexual contact (P less than 0.001). Giardial infection was also significantly related to oral-anal sex (P less than 0.001). No relation was seen between the presence or absence of gastrointestinal symptoms and infection with pathogenic protozoa. Factors associated with parasitic infection differed little from those found in previous studies, although significance levels were considerably higher because of the larger size of our study group.

Adult↗