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Thoracic Actinomycosis

Last updated Dec. 23, 2018

Actinomycosis is a rare and chronic infection, caused predominantly by the bacterium Actinomyces israelii and to a lesser extent by other Actinomyces species. Thoracic Actinomycosis is a subtype of actinomycosis that specifically affects the lungs and airways.


What are the other Names for this Condition? (Also known as/Synonyms)

  • Bronchial Actinomycosis
  • Laryngeal Actinomycosis
  • Respiratory Tract Actinomycosis

What is Thoracic Actinomycosis? (Definition/Background Information)

  • Actinomycosis is a rare and chronic infection, caused predominantly by the bacterium Actinomyces israelii and to a lesser extent by other Actinomyces species. Thoracic Actinomycosis is a subtype of actinomycosis that specifically affects the lungs and airways
  • The bacteria exist naturally in the mucous lining of the nose, throat, mouth, digestive tract, and female reproductive tract, and are not normally harmful. These anaerobic bacteria have the ability to grow in the absence of oxygen, or in reduced concentrations of oxygen
  • However, any injury, trauma, or surgical procedure can cause the bacterial cells to enter deeper tissues, where they are not normally found. Since these bacteria can grow without oxygen, they can thrive in such environments, resulting in infection
  • In majority of cases, Thoracic Actinomycosis occurs as a result of an accidental aspiration of the causative bacteria through food or water, particularly in individuals with poor dental hygiene. The water droplet or food particle can enter the respiratory tract and infect the voice box (larynx), main air passageways (bronchi), or the lungs
  • Individuals with poor dental hygiene, scarring of lungs, chronic lung disease, infection in the lungs, and alcohol dependence or addiction are at increased risk of contracting Thoracic Actinomycosis. Some typical symptoms of the infection include chest pain, shortness of breath, cough, fever, and weight loss
  • The condition is diagnosed through imaging of the lungs, observation of drainage from abscess under the microscope (to check for “sulfur granules”), culture of phlegm or sputum samples, bronchoscopy with culture and a lung biopsy, if required
  • Intravenous and oral antibiotics are used for treatment of Thoracic Actinomycosis. If left untreated, the infection can destroy the lungs and spread to other parts of the body. However, appropriate treatment can result in a cure and lead to an excellent prognosis

Who gets Thoracic Actinomycosis? (Age and Sex Distribution)

  • Thoracic Actinomycosis is a rare infection, which constitutes about 20% of all cases of actinomycosis
  • The condition can occur in any age group and is more common in males than females
  • However, adults (particularly men between age 30 and 60 years) are more susceptible to the infection than children

What are the Risk Factors for Thoracic Actinomycosis? (Predisposing Factors)

Certain underlying conditions can increase the risk for Thoracic Actinomycosis and these include:

  • Poor dental hygiene; formation of dental abscess
  • Alcohol dependence or addiction
  • Having an endobronchial stent in place
  • Scarred tissue in lung as in bronchiectasis (damaged airways)
  • Aspiration of foreign body (such as fish bone)
  • Chronic lung conditions such as emphysema (an infection of lungs which leads to destruction of the walls of air sacs)
  • Compromised immunity owing to HIV/AIDS, organ transplantation, chemotherapy or radiation therapy

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Thoracic Actinomycosis? (Etiology)

Thoracic Actinomycosis is caused by anaerobic bacteria, belonging to the family Actinomycetaceae. These bacteria are gram-positive and can survive in very low concentrations of oxygen. The following are some bacterial species known to cause actinomycosis:

  • Actinomyces israelii, which is responsible for majority of infections
  • Actinomyces gerencseriae
  • Actinomyces viscosus
  • Actinomyces meyeri
  • Actinomyces naeslundii

Under normal circumstances, the bacteria are present in the mucous lining of the mouth, throat, digestive system, and the female reproductive tract, without causing harm. However, they gain entry into the airways and lungs when the mucosal barrier gets disrupted due to the following factors:

  • Accidental aspiration of contaminated food particle or droplets of contaminated liquid (with the bacteria)
  • Aspiration of foreign bodies such as fish bone
  • Bronchial stent placement
  • An infection elsewhere in the body that spreads to the lungs through the bloodstream

Once in the airways, an injury or damage caused by certain pre-existing conditions result in the development of Thoracic Actinomycosis.

Note: The infection is not contagious, since the anaerobic bacteria are unable to survive outside the human body.

What are the Signs and Symptoms of Thoracic Actinomycosis?

The signs and symptoms of Thoracic Actinomycosis can be varied, and sometimes, be very subtle. These may include:

  • Chest pain, which increases on taking deep breaths
  • Cough, which may be associated with phlegm (phlegm may contain blood)
  • Dry cough possibly with blood
  • Fever and night sweats
  • Loss of appetite; loss of weight
  • Breathlessness
  • Fatigue

How is Thoracic Actinomycosis Diagnosed?

The diagnosis of Thoracic Actinomycosis can be difficult and may take weeks or months. The following methods may be employed to diagnose the infection:

  • A thorough physical examination and an assessment of symptoms
  • Evaluation of the affected individual’s medical history
  • Chest X-ray: It may show signs of lung infection or any other underlying lung disease
  • Complete blood count: It can help give a picture of the burden of infection in the body
  • Computed tomography (CT) scan of chest: A CT scan of the chest can give detailed images of the lung tissue and help categorize the presence and absence of infection, including the extent of infection
  • Observing pus or drainage from abscess under microscope to check for “sulfur granules”. The sulfur granules are so named for their characteristic appearance (round, yellow granules), and not because they contain sulfur
  • Sputum culture and gram stain
  • Bronchoscopy with culture: Easing a long tube through the windpipe into the lungs to see directly inside the organ. Bronchial washings and tissue for microbiological and pathological tests may also be collected. The procedure is performed under anesthesia
  • Lung biopsy and histopathology: It involves taking a small lung tissue from the diseased area preferably through bronchoscopy. The tissue is observed under microscope to identify the causative agent

Note: Thoracic Actinomycosis may mimic some malignant lung conditions, and therefore, ruling out other health conditions may often be necessary to arrive at a final diagnosis.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Thoracic Actinomycosis?

The possible complications of Thoracic Actinomycosis include:

  • Destruction of lungs: The infection can destroy the lung tissue leading to fibrosis
  • Emphysema: The infection can cause destruction of the walls of air sacs leading to entrapment of air in lungs, and hence, resulting in chronic difficulty in breathing
  • Pneumonia
  • Spread of infection from lungs to chest wall, to the spine, etc.
  • Infection at other body locations: The bacteria can travel through blood and lymph, causing infection in the brain (brain abscess), infection of the membrane covering of brain (meningitis), and infection of the bones (osteomyelitis)

How can Thoracic Actinomycosis be Treated?

Thoracic Actinomycosis is treated with antibiotics to eliminate the infection.

  • Typically, the antibiotic (such as penicillin, tetracycline, or erythromycin) is administered intravenously for about 4-6 weeks
  • Following this regimen, an oral antibiotic is generally prescribed for a few months

Additionally, surgery may be necessary to drain fluid from the lung and control the infection, in some cases.

How can Thoracic Actinomycosis be Prevented?

Thoracic Actinomycosis may be preventable by practicing the following:

  • Maintaining good dental hygiene by flossing and brushing teeth daily, getting regular dental check-ups, and avoiding sugary food/drinks that promote tooth decay
  • Efficiently managing pre-existing conditions that may pose a risk for contracting the infection
  • Seeking prompt medical attention as the first signs of infection become apparent

Completing the full course of prescribed antibiotics regimen, to eliminate the infection causing bacteria from deep tissue, as well as to prevent relapse of infection and development of drug-resistant bacterial species.

What is the Prognosis of Thoracic Actinomycosis? (Outcomes/Resolutions)

  • The prognosis of Thoracic Actinomycosis is good with an early diagnosis and prompt treatment using antibiotics
  • However, the outcomes may be influenced by factors such as underlying medical conditions and compromised immune system

Additional and Relevant Useful information for Thoracic Actinomycosis:

Actinomycosis commonly occurs in animals (mostly cattle) and rarely in humans. In cattle, the bacteria target areas around the head, especially the jaw, which gives rise to the name “big/lumpy jaw”.

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: June 6, 2017
Last updated: Dec. 23, 2018