Prospective Study of the Prevalence, Genotyping, and Clinical Relevance of Dientamoeba fragilis Infections in an Australian Population

Abstract

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.Dientamoeba fragilis is a trichomonad parasite found in the gastrointestinal tract of humans and implicated as a cause of gastrointestinal disease. Dientamoeba fragilis has been found in most parts of the world in both rural and cosmopolitan areas (10). The prevalence of this organism in Australia varies greatly, from 0.4% to 16.8%, in patients presenting with gastrointestinal complaints (1,22).No cyst stage has been observed, and only the trophozoites are detected in stool samples. Definitive diagnosis is based on prompt fixation and permanent staining, as the trophozoites degenerate rapidly, within hours of been passed, and demonstration of their characteristic nuclear structure cannot be achieved in unstained preparations (24). Daily shedding of D. fragilis trophozoites has been shown to be highly variable, with intermittent shedding occurring regularly, necessitating multiple sampling for maximum chances of detection (20).Molecular techniques for the diagnosis of D. fragilis show much promise, with PCR demonstrating excellent sensitivity and specificity (18). Such techniques have been used successfully for the diagnosis of other pathogenic protozoa (11,19).Molecular genotyping and sequence analysis have demonstrated that D. fragilis exists as two genetically distinct forms (9,15,18,26). Stark et al. (18) sequenced the SSU rRNA gene of seven Australian D. fragilis isolates, and the data generated from the seven showed no variation among them. These observations support the notion that D. fragilis is a clonal species. The sequences from the Australian isolates, however, differed from the sequence of the D. fragilis strain Bi/PA (ATCC 30948; GenBank accession no. U37461) and were found to be similar to those found in a recent study in the Netherlands (15). The true incidence of the wild-type and variant forms in Australia needs to be established and to determine if such variation has any influence on the pa...

Fecal calprotectin among patients infected with some protozoan infections

“…Human to human and human to animal transmission was not obvious (Yoshikawa et al, 2004). Diagnosis of B. hominis overlaps with other causatives of diarrhea specially the size of the cysts that measures 3 to 10 μm which is close to oocyst of Cyclospora, Entamoeba histolytica and other protozoan parasites (Tan, 2004 (Stark et al, 2005) in another study, eosinophilia was present in half of the infected children participating in the case. D. fragilis does not penetrate the host tissue directly; therefore, some of these symptoms may be caused from irritation which then leads to colonic motility (Johnson, 2016).…”

“…The multiple samples are required because of parasite detection being difficult, therefore, a sample might be obtained each day to help increase the sensitivity Patients can also be tested for E. vermicularis since the two parasites are known to coincide. (Stark et al, 2005) Unlike the majority of parasitic infections, D. fragilis is more prevalent in well-developed countries as opposed to disadvantaged and resource poor nations. (Lagacé-Wiens et al, 20006) The parasite is also endemic in crowded communities (i.e institutions), populations with unsatisfactory sanitation conditions, and individuals who travel to underprivileged countries (Mack, 2016).…”

Treatment of Dientamoeba fragilis in Patients with Irritable Bowel Syndrome

“…27 In primary care in Holland, a prevalence rate of 14% was found among patients without GI symptoms consulting general practice. 28 The parasite has been associated with acute and chronic gastrointestinal symptoms ( 2 weeks) most frequently abdominal pain, diarrhea, and loose stools, 24,26,27,[29][30][31] however the parasite is also found in asymptomatic individuals 24,27,28,32 and the pathogenicity of this parasite is debated.…”

Repeated Dientamoeba fragilis Infections: A Case Report of Two Families from Sydney, Australia

“…4 Diagnosis of D. fragilis infection was made based on the finding of binucleate, pleomorphic, granular, amoeboid cells, typical of D. fragilis in the initial stained smear. 4 The patient was treated with metronidazole, symptoms improved, and on follow up examination of stool sample (n=1) no parasites were detected, indicating that the infection was successfully cleared.…”