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Pulmonary actinomycosis

Actinomycosis - pulmonary; Actinomycosis - thoracic

Pulmonary actinomycosis is a rare lung infection caused by Actinomyces bacteria.

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Causes

Pulmonary actinomycosis is caused by certain bacteria normally found in the mouth and gastrointestinal tract. The bacteria often do not cause harm. But poor dental hygiene and tooth abscess can increase your risk for lung infections caused by these bacteria.

People with the following health problems also have a higher chance of developing the infection:

• Alcohol use disorder
• Scars in the lungs (bronchiectasis)
• Chronic obstructive pulmonary disease (COPD)

The disease is rare in the United States. It may occur at any age, but is most common in people 30 to 60 years old. Men get this infection more often than women.

Symptoms

The infection often comes on slowly. It may be weeks or months before diagnosis is confirmed.

Symptoms may include any of the following:

• Chest pain when taking a deep breath
• Cough with phlegm (sputum)
• Fever
• Shortness of breath
• Unintentional weight loss
• Lethargy
• Night sweats (uncommon)

Exams and Tests

Your health care provider will perform a physical exam and ask about your medical history and symptoms. Tests that may be done include:

• Bronchoscopy with culture
• Complete blood count (CBC) with differential
• Chest x-ray
• Chest CT scan
• Lung biopsy
• Modified AFB smear of sputum
• Sputum culture, the most common organism is Actinomyces israelii 
• Tissue and sputum Gram stain
• Thoracentesis with culture
• Tissue culture

Treatment

The goal of treatment is to cure the infection. It may take a long time to get better. To be cured, you may need to receive the antibiotic penicillin through a vein (intravenously) for 2 to 6 weeks. Then you may need to take penicillin by mouth for a long period. Some people need up to 18 months of antibiotic treatment.

If you cannot take penicillin, your provider will prescribe other antibiotics.

Surgery may be needed to drain fluid from the lungs and control the infection.

Outlook (Prognosis)

Most people get better after treatment with antibiotics.

Possible Complications

Complications may include:

• Brain abscess
• Destruction of parts of the lungs
• COPD
• Meningitis
• Osteomyelitis (bone infection)

When to Contact a Medical Professional

Contact your provider if:

• You have symptoms of pulmonary actinomycosis
• Your symptoms get worse or do not improve with treatment
• You develop new symptoms
• You have a fever of 101°F (38.3°C) or higher

Prevention

Good dental hygiene may help reduce your risk for actinomycosis.

Related Information

References

Brook I. Actinomycosis. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 304.

Russo TA, Hu JC. Agents of actinomycosis. In: Blaser MJ, Cohen JI, Holland SM et al, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 10th ed. Philadelphia, PA: Elsevier; 2026:chap 260.

Review Date: 3/1/2026  

Reviewed By: Jatin M. Vyas, MD, PhD, Roy and Diana Vagelos Professor in Medicine, Columbia University Vagelos College of Physicians and Surgeons, Division of Infectious Diseases, Department of Medicine, New York, NY. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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