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Actinomycosis is a bacterial infection that results in collections of pus in the body.

Abdominal Abscess

Abdominal Abscess

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Actinomycosis is most often caused by infection by specific bacteria. This is normally present in the mouth and, sometimes, in the intestines. The jaw is most commonly involved, with lung and abdominal infections being less common. Rarely, women may develop abscesses in the reproductive organs or bladder.

Risk Factors

Factors that may increase your risk of actinomycosis include:

  • Having a dental disease or recent dental surgery
  • Liquids or solids that are sucked into the lungs
  • Having bowel surgery
  • Swallowing fragments of chicken or other bones
  • Having an intrauterine contraceptive device (IUD) in place for many years
  • Diabetes
  • Having a weakened immune system
  • Malnutrition
  • Tissue damage
  • Chronic granulomatous disease or other disorder that affects the immune system (children)

Actinomycosis may cause:

  • Hard swellings that are usually painless and located around the mouth, neck, or jaw
  • Swellings that may produce pus containing tiny, yellowish particles
  • Drainage of pus through the skin of the chest or abdomen
  • Fever
  • Weight loss
  • Cough that produces sputum or blood
  • Noticeable swelling or firm mass in the abdomen, especially the lower part

You will be asked about your symptoms and medical history. A physical exam will be done. Tests may include:

  • Analyses of pus, sputum, or tissue
  • X-ray

Talk with your doctor about the best treatment plan for you. Actinomycosis is treated with long-term antibiotics and by draining pus-containing abscesses.


The best way to reduce your chances of developing actinomycosis is to prevent dental disease by practicing good dental hygiene and regularly visiting your dentist. You should:

  • Brush your teeth twice a day
  • Floss daily
  • Replace your toothbrush regularly


Family Doctor—American Academy of Family Physicians

Mouth Healthy—American Dental Association


Canadian Dental Association

Health Canada


Actinomycosis. DynaMed website. Available at: Updated October 20, 2011. Accessed June 10, 2015.

Hall V. Actinomyces—gathering evidence of human colonization and infection. Anaerobe. 2008;14(1):1-7.

Naik NH, Russo TA. Bisphosphonate-related osteonecrosis of the jaw: the role of actinomyces. Clin Infect Dis. 2009;49(11):1729-1732.

Sullivan DC, Chapman SW. Bacteria that masquerade as fungi: actinomycosis/nocardia. Proc Am Thorac Soc. 2010;7(3):216-221.

Last reviewed July 2015 by David L. Horn, MD, FACP

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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