Colonization of the uterus by the oral protozoan Entamoeba gingivalis

Pap smears occasionally reveal protozoa of the genus Entamoeba in the uterus of intrauterine device (IUD) users, but definitive identification of the species involved has not been possible. Using riboprinting, a technique that compares ribosomal RNA gene sequences, we present evidence that the organism is Entamoeba gingivalis, an inhabitant of the mouth. Colonization most likely occurs via orogenital contact and requires the presence of an IUD and a concomitant bacterial infection.