Actinomycosis is a chronic infection caused mainly by Actinomyces israelii, anaerobic bacteria that normally reside on the enamel of teeth, gums, tonsils, and membranes lining the intestines and vagina.
These bacteria cause infection only when the surface of the tissue on which they reside is broken, enabling them to enter other, deeper tissues, which have no defenses against them. As the infection spreads, scar tissue and abnormal channels (called fistulas or tracts) form. After months to years, fistulas may eventually reach the skin and allow pus to drain. Pockets of pus (abscesses) may develop in the chest, abdomen, face, or neck.
Men are affected most often, but actinomycosis occasionally develops in women who use an intrauterine device (IUD).
Actinomycosis has several forms. All cause abscesses.
The bacteria infect the intestine, usually the area near the appendix, and the lining of the abdominal cavity (peritoneum). Chronic abdominal pain, fever, vomiting, diarrhea or constipation, and severe weight loss are common symptoms. Fistulas may form from the interior of the abdomen to the skin above it and between the intestine and other organs.
The bacteria spread to the uterus, usually from an IUD that has been in place for years. Abscesses and scar tissue may form in the fallopian tubes, ovaries, and nearby organs such as the bladder and ureters. Fistulas may form between these organs. Symptoms include chronic abdominal or pelvic pain, fever, weight loss, and vaginal bleeding and discharge.
Usually, small, hard, sometimes painful swellings develop in the mouth and on the face, neck, or skin below the jaw (lumpy jaw). These swellings may soften and discharge pus that contains small, round, yellowish granules. The infection may extend to the cheek, tongue, throat, salivary glands, skull, bones of the neck (cervical vertebrae) and face, brain, or the space within the tissues covering the brain (meninges).
This form affects the chest (thorax). People have chronic chest pain and fever. They lose weight and cough, sometimes bringing up sputum. People probably become infected when they inhale fluids that contain bacteria from their mouth. Abscesses may form in the lungs and eventually spread to the membrane between the lungs and chest wall (pleura). There, abscesses cause irritation (pleuritis), and infected fluid collects (called an empyema). Fistulas may form, enabling the infection to spread to the ribs, skin of the chest, and spine.
Rarely, the bacteria are carried in the bloodstream to infect other organs, such as the brain, lungs, liver, kidneys, and heart valves.
Doctors suspect the infection in people who have typical symptoms. Then, x-rays are taken, and samples of pus or tissue are obtained and checked for Actinomyces israelii. Often, a needle is inserted through the skin to take a sample from an abscess or infected tissue. Sometimes computed tomography (CT) or ultrasonography is used to help doctors place the needle in the infected area. Sometimes surgery is necessary to remove a sample.
Characteristic x-ray findings and identification of the bacteria in a sample confirm the diagnosis.
Treatment consists of draining abscesses with a needle (usually inserted through the skin) and giving high doses of antibiotics such as penicillin or tetracycline. Antibiotics may be needed for as long as 6 to 12 months.
CT or magnetic resonance imaging (MRI) may be used to determine whether abscesses are resolving. Surgery, with or without antibiotics, may be necessary, particularly if the infection affects critical areas such as the spine.
If actinomycosis is diagnosed early and treated appropriately, most people recover fully.
Last full review/revision September 2008 by Matthew E. Levison, MD