Detection of Dientamoeba fragilis: a comparison between real-time polymerase chain reaction and conventional diagnostic assays.

Objectives: The pathogenic role of Dientamoeba fragilis has been controversial for a long time but it was recently reassessed because of a large number of patients with D. fragilis infection (without other enteropathogenic agents) reporting gastro-intestinal signs and symptoms solved by a targeted therapy. The laboratory diagnosis of dientamoebiasis is traditionally performed by microscopic examination after permanent staining and/or culture. The fact that conventional diagnosis is timeconsuming and requires well-trained personnel led us to evaluate the usefulness of a real-time PCR assay compared to the methods currently used in our laboratory for the diagnosis of infection by D. fragilis. Methods: Conventional diagnostic methods for the detection of intestinal parasites currently used in our laboratory (microscopic examination of fresh and concentrated faecal material and cultivation in Robinson’s medium, followed by acridine orange staining when structures resembling D. fragilis were observed) were performed on 988 faecal samples belonging to 508 patients with a clinical suspicion of intestinal parasitosis in a period of 41 months. The DNA extracted from the same samples was used in a previously described real-time PCR assay targeting the 5.8S rRNA gene of D. fragilis [1]. Results: Conventional methods detected D. fragilis in 72 samples of 47 patients while real-time PCR revealed the presence of the protozoan in 189 samples of 107 patients (21% of the analyzed patients). In 60 of these cases dientamoebiasis was diagnosed by real-time PCR alone. Discussion: In our experience, the evaluated real-time PCR assay showed a higher diagnostic sensitivity than microscopic examination and culture which had underestimated the number of D. fragilis infections. This molecular assay could be a rapid and effective tool in our laboratory to be associated with conventional ones for an accurate diagnosis of infection by D. fragilis in faecal samples belonging to patients presentingwith signs and symptoms and/or risk factors for intestinal parasitoses, taking into account that dientamoebiasis is suitable to be eradicated by a targeted therapy. Reference(s) [1] Verweij et al. Mol Cell Probes 2007; 21: 400–404.