Actinomycosis is a rare bacterial infection caused by a group of bacteria known as Actinomyces. These bacteria are normally found in the mouth and gastrointestinal tract but can cause disease when they enter the body through breaks in the skin or mucous membranes. The infection often leads to the formation of painful abscesses, particularly in the jaw, neck, or abdomen. Symptoms of actinomycosis may include swelling, fever, and the formation of pus-filled lumps. Diagnosis typically involves imaging studies and laboratory tests to identify the bacteria. Treatment usually consists of long-term antibiotics, and in some cases, surgical intervention may be necessary to remove infected tissue.