Eubacterium nodatum mimics Actinomyces in intrauterine device-associated infections and other settings within the female genital tract.

Eubacterium nodatum is an obligately anaerobic, gram-positive, branching rod that markedly resembles Actinomyces, particularly Actinomyces israelii, in its cellular and colonial characteristics. Its isolation from the female genital tract was examined for a study period in which use of intrauterine contraceptive devices (IUDs) was common, and additional characteristics of the organism were investigated. Fifteen genital isolates of E nodatum were all associated with the presence of a foreign body, usually an IUD (12 patients). Six of these 12 patients had presented with clinically severe pelvic inflammatory disease. The remaining six had signs and symptoms related to IUD use and/or had a report of probable Actinomyces (five patients) by a Papanicolaou smear, demonstrating that E nodatum can be mistaken for Actinomyces in a Papanicolaou-stained smear. The three other patients had different types of foreign bodies. The frequency of isolation from cultures associated with IUD use during the study period was five (6.4%) of 78 for Actinomyces versus the 12 (15.4%) of 78 for E nodatum. In vitro-prepared E nodatum was not demonstrated to cross-react with A israelii or A naeslundii antisera. Both E nodatum and A israelii were shown to adhere in vitro to an inanimate object, indicating their propensities to colonize a foreign body. The present data, with the previous reports of isolation of E nodatum from cases of lumpy jaw and severe periodontitis, suggest that it is an opportunistic pathogen very much like A israelii.