actinomycosis (ăkˌtənōmĪkōˈsĭs) [key], chronic suppurative infection that occurs around the face and neck. The disease is characterized by the formation of abscesses, or pus-filled cavities, below the surface of the skin. These abscesses spread rapidly and form channels that discharge a yellow granular pus on the surface of the skin. In humans these granules consist of Actinomyces israelii, a bacterium that used to be considered a fungus. Actinomycosis also sometimes affects the lungs, appendix, or the pelvic region, especially in women with certain kinds of intrauterine devices. Treatment consists of prolonged therapy with massive doses of penicillin and drainage by surgery. Actinomycosis also occurs in horses, cattle, swine, and dogs; it resembles human actinomycosis, but is caused by various other species of Actinomyces.