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Last updated March 25, 2018

Approved by: Maulik P. Purohit MD MPH


Microscopic pathology image of a section showing Actinomycosis.

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

  • Actinomyces Infection
  • Rivalta Disease

What is 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
  • They 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
  • Although Actinomycosis typically affects the head and neck area, the infection can also affect other areas, such as the chest, abdomen and pelvic region. Based on the area of the body affected, Actinomycosis is divided into the following subtypes:
    • Cervicofacial (neck, jaw, mouth)
    • Extrafacial bone and joint
    • Thoracic (lungs)
    • Digestive tract (abdominal)
    • Pelvic (pelvis)
    • Central nervous system (CNS)
    • Cutaneous
  • The infection occurs more often in men. However, women using intra-uterine devices (IUDs) may be prone to Actinomycosis as well
  • The bacteria are slow-growing and the infection leads to the formation of hard, red or purple pus-filled abscess in the affected tissue. The abscess may drain and this can be accompanied by pain and fever
  • Examination of the fluid drainage under microscope and culture of affected tissue specimen and imaging techniques may be employed to diagnose Actinomycosis. The pus or drainage is checked for “sulfur granules”. These granules do not contain sulfur, but are thus named for their characteristic appearance
  • Prolonged treatment with antibiotics is necessary to remove the infection. In some cases, the abscess may need to be surgically drained or removed
  • With prompt diagnosis and sustained treatment, Actinomycosis is curable. However, if the infection becomes generalized via spread of bacteria through the bloodstream, it can spread to other organs and tissues. In such cases, the recovery can be prolonged 

Who gets Actinomycosis? (Age and Sex Distribution)

  • Actinomycosis is a rare infection that is known to occur worldwide
  • The occurrence of this infection has been documented chiefly in males, who are between 20 to 60 years of age
  • However, the use of intrauterine devices (IUDs) has resulted in an increased frequency of Actinomycosis in females. The infection affects the genitourinary tract in such cases

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

The following are some known risk factors for Actinomycosis:

  • Poor dental hygiene; having undergone dental work recently
  • Male gender
  • Use of endobronchial stent; use of pancreatic stent
  • Use of intrauterine devices by women
  • Malnutrition
  • Alcoholism
  • Certain pre-existing conditions such as poorly-controlled diabetes
  • Mandibular (jaw) injuries
  • Appendicitis, appendix removal
  • Infections such as pneumonia
  • 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 Actinomycosis? (Etiology)

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, when the mucous lining gets damaged owing to numerous factors, such as injury, trauma, or surgery, the bacteria enter the inner/deeper tissues
  • Being anaerobic, they can survive and multiply in the low oxygen conditions of deep tissue, causing the development of scar tissue and fistula (or abnormal tracts)
  • Abscess formation can take place with the accumulation of pus, which may drain when the tracts reach the surface of skin. This process may take months to years

Depending on the region of body affected, Actinomycosis is classified into the following types:

  • Cervicofacial type (affecting the face and neck region): This type accounts for 50-70% of the reported cases and can be caused by poor dental hygiene, certain dental procedures, or injury to the jaw
  • Extrafacial bone and joint type: This type of Actinomycosis affects the bones and joints. It can spread from a primary infection site through blood, from the lungs to chest wall through contact, or through an infection causing a deep ulcer that exposes the underlying bone to bacteria
  • Thoracic type: In this type, the infection occurs in the airways or lungs by accidental aspiration of food, droplets or secretions contaminated with bacteria, owing to poor dental hygiene. Approximately, up to 20% of the cases belong to this category. The infection can spread from the lungs to the chest wall and spine through contact
  • Digestive tract type: It can be caused owing to infections such as appendicitis and perforated appendix, including due to surgical removal of the appendix or ingestion of a foreign object (such as a chicken bone). About 20% of all cases of Actinomycosis are estimated to belong to this category. The most common infections are of the cecum, appendix, and colon; although, esophageal, pancreatic, hepatic, stomach, gallbladder, and abdominal wall Actinomycosis have also been reported
  • Pelvic type: More common in women, this type of infection forms about 10% of the reported cases. The pelvic type of infection is often associated with the use of intra-uterine contraceptive devices (IUDs). However, infection in the pelvic region is not limited to females, since some cases of testicular Actinomycosis is also reported. Additionally, the urinary bladder may be involved. There is also a possibility of abdominal wall infection because of long-term IUD use
  • Central nervous system type: This infection type is rare, and in most cases, secondary to either a lung infection that spreads to the brain via blood, cervicofacial Actinomycosis that spreads through contact, or owing to penetrating head injury/trauma
  • Cutaneous type: This infection type originates in the skin and soft tissue, forming abscesses or lesions

When the bacteria get into the bloodstream from an infected tissue, they can travel to other organs and cause generalized infection. The following are some organs that may be affected:

  • Heart and heart valves
  • Kidneys

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

What are the Signs and Symptoms of Actinomycosis?

The signs and symptoms of Actinomycosis may vary depending on the site and severity of infection. However, abscess formation is commonly present in all types of Actinomycosis.

Cervicofacial signs and symptoms may include:

  • Swelling of the mouth, face, jaw, and neck region: These swellings may be small and hard
  • Pain in the swollen areas
  • Pus leaking out of lesions in the skin, near the infected sites
  • Sulfur granules released in the pus (round, yellow granules): These granules do not actually contain sulfur, but are named so, because of their characteristic appearance

Extrafacial bone and joint signs and symptoms may include:

  • Inflammation of joints with joint pain
  • Stiffness of joints
  • Difficulty in movement, limited movement range
  • Arthritis

Thoracic signs and symptoms may include:

  • Chest pain
  • Cough, which may or may not be productive
  • Fever
  • Weight loss

Digestive tract signs and symptoms may include:

  • Long-term pain in the abdomen
  • Diarrhea
  • Constipation
  • Nausea
  • Vomiting
  • Weight loss, which can be severe

Pelvic signs and symptoms, which are most commonly observed in women, may include:

  • Pelvic pain
  • Vaginal discharge, bleeding
  • Constipation
  • Weight loss

Central nervous system signs and symptoms may include:

  • Headache
  • Vomiting
  • Weakness of some specific body region (focal weakness)
  • Numbness/loss of sensation
  • Seizures

Cutaneous (or skin) signs and symptoms may include:

  • Inflammation of skin
  • Abscesses on skin, with or without inflammation

How is Actinomycosis Diagnosed?

Actinomycosis is diagnosed on the basis of the following test and exams:

  • A thorough physical examination and assessment of symptoms
  • Evaluation of the affected individual’s medical history
  • Microscopic observation of pus, phlegm, or tissue samples, to check for the presence of sulfur granules. The tissue samples may have to be obtained surgically
  • Culture of fluid or tissue from infected area: These bacteria are slow to grow in culture, and it may take over 3 weeks to obtain a (positive) culture result
  • X-ray, computed tomography (CT), or magnetic resonance imaging (MRI) scans of the affected area, to ascertain location and number of abscesses, as well as differentiate inflammatory masses due to infection from the tumors

Note: Actinomycosis may mimic some malignant 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 Actinomycosis?

The following are some potential complications from Actinomycosis:

  • Formation of large lesions
  • The infection spreading to other organs away from the primary site of infection
  • Meningitis or inflammation of the meninges (outer membrane covering of brain)
  • Pneumonia
  • Jaundice
  • Scar tissue formation in the uterus

How is Actinomycosis Treated?

The treatment measure for Actinomycosis may include:

  • Prolonged use of antibiotics (anywhere from 2 months to over 12 months); typically, β-lactam (such as penicillin, amoxicillin) or tetracycline family of antibiotics are used
  • Surgical drainage of abscess; draining the abscess by inserting a needle
  • Surgical removal of infected tissue:
    • Surgery is sometimes necessary for cases in which large abscesses have developed, the infection has spread to organs and bones, and antibiotics alone are unsatisfactory
    • Surgery creates an aerobic environment, which is detrimental to bacterial growth. It also allows for the excision of lesions, drainage of sinuses, as well as containment and elimination of the disease
  • Hyperoxygen therapy to eliminate bacteria:
    • This therapy helps increase the concentration of oxygen in the infected tissues
    • The presence of oxygen results in higher amounts of oxygen-derived radicals that harm, and are specifically drawn to anaerobic organisms, such as Actinomyces
    • This method has only been approved as an adjunct to other forms of treatment

How can Actinomycosis be Prevented?

Actinomycosis can be prevented through adherence to the following factors:

  • Practicing proper dental hygiene: Maintaining proper dental hygiene always, and particularly, following a dental procedure, surgery, or tooth extraction
  • Educating oneself or monitoring self for any signs of discomfort following a surgery, and promptly reporting to the attending healthcare provider, so that infections may be detected early and treated appropriately
  • Avoiding the use of intra-uterine devices (when possible), in women; adopting alternative contraceptive practices

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 Actinomycosis? (Outcomes/Resolutions)

The prognosis of Actinomycosis is good with early diagnosis and prompt treatment in individuals with good overall health status.

  • The outcomes may be influenced by underlying medical conditions and/or compromised immunity
  • Additionally, a lack of treatment may allow the infection to spread to other organs and tissues, which may prolong the treatment and recovery process

Additional and Relevant Useful Information for 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”
  • The Actinomyces bacteria are either obligate anaerobes or microaerophilics that require very small amounts of oxygen. A. israelii was once placed in the fungal kingdom and may have close common ancestry with certain fungi
  • Since Actinomyces species are known to be part of the natural flora of the cecum, removal of the appendix may pose a risk of introducing the A. israelii into different sections of the intestine, potentially inducing an infection

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: March 25, 2018