Dientamoeba Fragilis Infection Workup

  • Author: David R Mack, MD, FRCPC; Chief Editor: Russell W Steele, MD   more...
 
Updated: May 28, 2010
 

Laboratory Studies

Blood tests

Blood test results are usually normal in patients with Dientamoeba fragilis infection. However, a CBC count with differential may reveal eosinophilia in as many as 50% of children infected with the parasite.

Stool evaluation

The usual method for confirming the diagnosis is examination of a permanently stained smear of fresh feces, preserved immediately, for the morphologic characteristics of D fragilis trophozoites. Newer, but experimental, techniques include immunofluorescence and real-time polymerase chain reaction (PCR) techniques.[4] Culture is not routinely available.

Preferred stool preparation involves a fresh sample that is immediately preserved with polyvinyl alcohol fixative, sodium acetate-acetic acid-formalin fixative, or Schaudinn fixative. Immediate preservation is necessary because, in unpreserved feces, the morphologic characteristics of the trophozoites do not persist, and they round up and become granular within 15 minutes at room temperature.

A single sample is diagnostic only 50-60% of the time. Three separate samples increase the yield to 70-85%, and 6 separate samples increase the yield to 90-95%.

Ensure that stool samples are collected on alternate days because D fragilis can be excreted in a cyclic pattern similar to G lamblia. The final portion of the stool evacuation may contain the most concentrated numbers of trophozoites. Collect stool specimens before radiologic procedures that use barium because barium interferes with trophozoite detection and may do so for several weeks.

Other medications that can interfere with parasite detection include antibiotics, antiprotozoan medication, antimalarials, mineral oil, bismuth-containing preparations, and nonabsorbable diarrheal medications. Process stool specimens in the laboratory with the formalin-ether sedimentation concentration technique and stain with either iron hematoxylin, trichrome, or celestin B.

Diagnostic characteristics

Diagnostic characteristics are a pleomorphic trophozoite ranging in diameter from 5-15 mm (range, 4-30 mm) that contains 1-4 nuclei. The most common form is binucleated. However, approximately 20-30% are uninucleated. Multinucleated forms also can be present. The nuclei are distinctive, with several (4-8) chromatin granules clumped in the center of each nucleus. The cytoplasm frequently contains numerous food vacuoles.

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Imaging Studies

Radiologic test findings are usually normal.

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Contributor Information and Disclosures
Author

David R Mack, MD, FRCPC  Professor, Departments of Pediatrics and Biochemistry, Microbiology, and Immunology, University of Ottawa Faculty of Medicine; Head, Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, Children's Hospital of Eastern Ontario, Canada

David R Mack, MD, FRCPC is a member of the following medical societies: American Gastroenterological Association, Canadian Association of Gastroenterology, and North American Society for Pediatric Gastroenterology and Nutrition

Disclosure: Axcan Honorarium to CHEO Foundation Review panel membership; Novartis Honorarium to CHEO Foundation Consulting; AstraZeneca Honorarium to CHEO Foundation Speaking and teaching; Merck Frosst Honorarium to CHEO Foundation Speaking and teaching; Schering Plough Honorarium to CHEO Foundation Review panel membership; Schering Plough Honorarium to CHEO Foundation Speaking and teaching; Abbott Speaking and teaching; Ross Nutritionals Honorarium to CHEO Foundation Review panel membership; Nestle Honorarium to CHEO Foundation Review panel membership; Nestle Honorarium to CHEO Foundation Speaking and teaching

Specialty Editor Board

Michael D Nissen, MBBS, FRACP, FRCPA  Associate Professor in Biomolecular, Biomedical Science & Health, Griffith University; Director of Infectious Diesases and Unit Head of Queensland Paediatric Infectious Laboratory, Sir Albert Sakzewski Viral Research Centre, Royal Children's Hospital

Michael D Nissen, MBBS, FRACP, FRCPA is a member of the following medical societies: American Academy of Pediatrics, American Society for Microbiology, Pediatric Infectious Diseases Society, Royal Australasian College of Physicians, and Royal College of Pathologists of Australasia

Disclosure: Nothing to disclose.

Mary L Windle, PharmD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine

Disclosure: Nothing to disclose.

Martin Weisse, MD  Program Director, Associate Professor, Department of Pediatrics, West Virginia University

Martin Weisse, MD is a member of the following medical societies: Ambulatory Pediatric Association, American Academy of Pediatrics, and Pediatric Infectious Diseases Society

Disclosure: Nothing to disclose.

Robert W Tolan Jr, MD  Chief, Division of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine

Robert W Tolan Jr, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Phi Beta Kappa, and Physicians for Social Responsibility

Disclosure: GlaxoSmithKline Honoraria Speaking and teaching; MedImmune Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; sanofi pasteur Honoraria Speaking and teaching; Baxter Healthcare Honoraria Speaking and teaching; Novartis Honoraria Speaking and teaching

Chief Editor

Russell W Steele, MD  Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine

Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association

Disclosure: None None None

References

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  19. Vandenberg O, Souayah H, Mouchet F, Dediste A, van Gool T. Treatment of Dientamoeba fragilis infection with paromomycin. Pediatr Infect Dis J. Jan 2007;26(1):88-90. [Medline].

 
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This is an illustration of the assumed life cycle of Dientamoeba fragilis, the cause of a protozoan parasitic infection.
 
 
 
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