Causes of actinomycosis

Actinomycosis is caused by a group of bacteria called actinomycetaceae.

Actinomycetaceae are found in manybody cavities, such as inside the mouth and, less commonly, the bowel.

In women, they can also be found in the womb and fallopian tubes (the tubes eggs are released throughinto the womb).

How actinomycosis spreads

Actinomycetaceae are anaerobic bacteria, which means they can't survive in oxygen-rich environments. They therefore don't cause illness when they'rein the mouth or intestinal tract.

However, if the bacteriabreak through the protective lining (mucous membrane) surrounding the cavities, they can penetrate deep intobody tissue.

As the deep layers of human tissue are low in oxygen, the bacteria are able to reproduce quickly and infect healthy tissue.


In an attempt to combat the infection, your immune system (the body's natural defence against infection and illness) will send infection-fighting cells to the source of the infection.But these cellsare unable tokill the bacteria and will quickly die.

As the infection-fighting cells die, they accumulate into a yellowish-coloured liquid (pus). Having failed to kill the infection, your immune system will attempt to limit its spread by using healthy tissue to form a protective barrier around the pus. This is how an Abscess (pus-filled swelling) develops.

Actinomycetaceae are able to penetrate the protective barrier of an abscess and move into more healthy tissue. Your immune system will attempt to counter the infection by producing more abscesses.

Sinus tracts

Your body will eventually need to get rid of the accumulation of pus. To do this, small channels called sinus tracts will develop that lead from the abscesses to the surface of your skin.

The sinus tracts will leak pus, as well as lumps of bacteria. This takes the form of a yellow powdery substance sometimes referred to as "sulphur granules".

Opportunistic infection

Actinomycosis is an opportunistic infection that doesn't cause symptoms unless the chance arises for it to penetrate body tissue.

Oral cervicofacial actinomycosis

Opportunities for oral cervicofacial actinomycosis include:

  • tooth decay , particularly if the decay is left untreated foryears
  • gum disease
  • dental abscess
  • tonsillitis
  • middle ear infection (otitis media)
  • dental surgery, such as a tooth extraction, or root canal treatment
  • jaw surgery or trauma

Thoracic actinomycosis

Most cases of thoracic actinomycosis are thought to be caused by small foodparticles or other ingested material that gets mixed up with the actinomycosis bacteria.

Rather than passing harmlessly down into the stomach, the particles are mistakenly passed down into the windpipe and the airways of the lungs.

People with long-term drug or alcohol problems are particularly at risk of developing thoracic actinomycosis.

This is because being drunk or intoxicated increases therisk of material beingaccidentally ingested into your lungs. Long-term alcohol misuse and drug misuse also weakens your immune system, making you more vulnerable to developing an infection.

Abdominal actinomycosis

Abdominal actinomycosis occurs when something tears the wall of the intestine (bowel), allowing the bacteria to penetrate into deep tissue.

The intestine can tear as the result of an infection, such as a burst appendix that damages theintestine wall. It can also be damaged through injury for example, if you were to mistakenly swallow a fish bone.

There have also been some reported cases of abdominal actinomycosis occurring as a complication of bowel or abdominal surgery.

Pelvic actinomycosis

Most cases of pelvic actinomycosis have been recorded in women who were usingan intrauterine device (IUD) form of contraception.

An IUD is a small, T-shaped contraceptive device made from plastic and copper that fits inside the womb. The women affected by the condition tend to be long-term users of an IUD (eight years or more).

One explanation for cases of pelvic actinomycosis in women who are usingan IUD is that, over time,it may damage the womb lining, allowing bacteria to penetrate deep tissue. However, no research has been carried out to find out whether or not this is the case.

It's important to notethat it's very rare to develop pelvic actinomycosis as a result of usinganIUD. For example, in England, millions of women use the device and there have only been a handful of reported cases of pelvic actinomycosis.It only tends to occur ifan IUD is left in place longer than the manufacturer recommends.

Content supplied by the NHS Website

Medically Reviewed by a doctor on 20 Jun 2016