Actinomycosis causes

Causative organism
Actinomycosis is primarily caused by any of several members of the bacterial genus Actinomyces. These bacteria are generally anaerobes. Actinomyces spp. normally live in the small spaces between the teeth and gums, causing infection only when they can multiply freely in anoxic environments. The three most common sites of infection are decayed teeth, the lungs, and the intestines.

Since Actinomyces bacteria are generally sensitive to penicillin, it is frequently used to treat actinomycosis.