Actinomycotic pulmonary abscess in an immunosuppressed patient.

The clinical history of a patient with rheumatoid arthritis and bacteriologic findings from a pulmonary abscess occurring during prednisone therapy are presented. Direct transthoracic aspiration of the lesion yielded a pure culture of Actinomyces odontolyticus. This is believed to be the first case of a deep visceral infection with this organism, an inhabitant of the normal mouth and gums. Immunosuppression of the host probably played a role in establishment of the infection.