Medical Lab Technology

Dientamoeba fragilis trophozoites, identified via trichrome stain, are small (5–15 µm) amoeba-like flagellates typically containing two nuclei with fragmented karyosomes (3–5 granules). They exhibit a grayish-blue or green-tinted cytoplasm with fine, granular, or vacuolated texture and possess broad-lobed, transparent pseudopodia, making them a, key, frequently, overlooked, cause, of, intestinal, disease.

Because D. fragilis has no known cyst stage and is fragile, permanent stains like trichrome are essential for diagnosis. Direct wet mounts are frequently inaccurate.

Because trophozoites are fragile, stool samples must be immediately fixed (e.g., in PVA) to preserve the characteristic nuclear structure.

The pathogenicity and clinical importance of D. fragilis continue to be investigated, including whether particular genotypes, subtypes, or strains of D. fragilis are associated with symptomatic infection in humans. Both asymptomatic and symptomatic infection (e.g., with various nonspecific gastrointestinal symptoms) have been reported. The reported clinical manifestations have sometimes been described as similar to those of colitis, appendicitis, or irritable bowel syndrome.