Merck Manual

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Larry M. Bush

, MD, FACP, Charles E. Schmidt College of Medicine, Florida Atlantic University

Reviewed/Revised May 2021 | Modified Sep 2022
Topic Resources

Actinomycosis is a chronic infection caused mainly by the anaerobic bacteria Actinomyces israelii. This species of bacteria normally resides in the crevices between the teeth and gums, on the tonsils, and on mucus membranes lining the intestines and vagina.

  • Infection occurs only when tissue is broken, enabling the bacteria to enter deeper tissues.

  • Abscesses form in various areas, such as the intestine or face, causing pain, fever, and other symptoms.

  • Symptoms suggest the diagnosis, and doctors confirm it by identifying the bacteria in a sample of infected tissue.

  • Abscesses are drained, and antibiotics are given.

  • With prompt diagnosis and appropriate treatment, most people recover fully.

Actinomyces 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.

Symptoms of Actinomycosis

Actinomycosis has several forms. All cause abscesses, scar tissue, and fistulas.

Abdominal actinomycosis

Actinomyces 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.

Pelvic actinomycosis

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.

Cervicofacial actinomycosis

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).

Thoracic actinomycosis

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.

The infection may spread extensively before it causes any symptoms. Symptoms include chest pain, fever, and a productive cough.

Generalized actinomycosis

Rarely, the bacteria are carried in the bloodstream to infect other organs, such as the brain, spine, lungs, liver, kidneys, and heart valves. In women, the reproductive organs may be infected.

Symptoms vary depending on which organs are affected. For example, people may have a headache, back pain, or abdominal pain.

Diagnosis of Actinomycosis

  • Examination and culture of a sample of sputum, pus, or tissue

  • Sometimes imaging tests

Doctors suspect actinomycosis in people who have typical symptoms. Then, samples of sputum, pus, or tissue are obtained and checked for various species of Actinomyces, such as 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. The sample is examined under a microscope and is sent to a laboratory where bacteria, if present, can be grown (cultured).

Identification of the bacteria in the sample of sputum, pus, or tissue confirms the diagnosis.

Sometimes imaging tests (x-rays or CT) are done to determine the number, size, and exact location of abscesses.

Treatment of Actinomycosis

  • Drainage of abscesses

  • Antibiotics

Treatment of actinomycosis consists of

  • Draining abscesses with a needle (usually inserted through the skin) or with surgery

  • Giving high doses of antibiotics

Antibiotics such as penicillin or tetracycline must be taken for at least 2 months and may be needed for more than 12 months.

CT or magnetic resonance imaging (MRI) may be used to determine whether abscesses are resolving. Surgery may be necessary, particularly if the infection affects critical areas such as the spine.

Women who have pelvic actinomycosis have their IUD removed and are given penicillin. An extensive pelvic infection may require additional drainage of abscesses. Sometimes the uterus, fallopian tubes, and ovaries need to be removed.

If actinomycosis is diagnosed early and treated appropriately, most people recover fully. Recovery is related to which parts of the body are affected. Recovery is best when only the face and neck are affected and worst when the infection is generalized, especially if it affects the brain.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Emtet-500, Panmycin, Sumycin
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