Actinomycosis is caused by a group of bacteria called actinomycetaceae.

Actinomycetaceae are found in many body 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 through into 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’re in the mouth or intestinal tract.

However, if the bacteria break through the protective lining (mucous membrane) surrounding the cavities, they can penetrate deep into body tissue.

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

Abscesses

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 cells are unable to kill 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 for years
• 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 food particles 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 the risk of material being accidentally 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 the intestine 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 using an 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 using an 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 note that it’s very rare to develop pelvic actinomycosis as a result of using an IUD. 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 if an IUD is left in place longer than the manufacturer recommends.

In its initial stages, actinomycosis can be a challenging condition to diagnose correctly because it shares symptoms with other, more common conditions.

These include:

• cancer
• appendicitis (inflammation of the appendix)
• pneumonia (infection of the lungs)
• pelvic inflammatory disease (a bacterial infection of the female reproductive system, such as the womb or fallopian tubes)

As actinomycosis can be difficult to diagnose, it’s often only discovered during tests or surgery to check for other conditions.

For example, many cases of actinomycosis are detected when biopsies are carried out to check for cancer. A biopsy is where a small tissue sample is removed so it can be examined under a microscope.

Actinomycosis can usually be more confidently diagnosed in its later stages, after the sinus tracts have appeared in the surface of the skin.

This is because the sulphur granules produced by the sinus tracts during an actinomycosis infection have a distinctive shape that can be identified under a microscope.

Actinomycosis is a rare type of bacterial infection caused by a group of bacteria called actinomycetaceae.

Most bacterial infections are confined to one part of the body because the bacteria are unable to penetrate the body’s tissue.

However, actinomycosis is unusual in that the infection is able to move slowly but steadily through body tissue.

Symptoms of actinomycosis vary depending on the type of infection, but can include:

• swelling and inflammation of affected tissue
• tissue damage that results in scar tissue
• formation of abscesses (pus-filled swellings)
• small holes or tunnels that develop in tissue and leak a type of lumpy pus

Read more about the symptoms of actinomycosis.

Types of actinomycosis

In theory, actinomycosis can develop almost anywhere inside the tissue of the human body. But the condition tends to affect certain areas of the body and can be classified into four main types.

They are:

• oral cervicofacial actinomycosis
• thoracic actinomycosis
• abdominal actinomycosis
• pelvic actinomycosis

These are described below.

Oral cervicofacial actinomycosis

Oral cervicofacial actinomycosis is where the infection develops inside the neck, jaw or mouth. In the past, if the condition developed in the jaw it was known as lumpy jaw.

Most cases of oral cervicofacial actinomycosis are caused by dental problems, such as tooth decay or a jaw injury.

Oral cervicofacial actinomycosis is the most common type of actinomycosis, accounting for 50-70% of all cases.

Thoracic actinomycosis

Thoracic actinomycosis is where the infection develops inside the lungs or associated airways.

Most cases of thoracic actinomycosis are thought to be caused by people accidentally inhaling droplets of contaminated fluid into their lungs.

Thoracic actinomycosis accounts for an estimated 15-20% of cases.

Abdominal actinomycosis

Abdominal actinomycosis is where the infection develops inside the abdomen (tummy).

This type of actinomycosis can have a range of potential causes. It can develop as a secondary complication of a more common infection, such as appendicitis, or after accidentally swallowing a foreign object, such as a chicken bone.

Abdominal actinomycosis accounts for an estimated 20% of all cases.

Pelvic actinomycosis

Pelvic actinomycosis is where the infection develops inside the pelvis.

It usually only occurs in women because most cases are caused when the actinomyces bacteria are spread from the female genitals into the pelvis.

Most cases of pelvic actinomycosis are thought to be associated with the long-term use of an intrauterine device (IUD). This type of contraceptive is often known as the coil.

Pelvic actinomycosis usually only occurs if the coil is left in for longer than the manufacturer recommends.

Pelvic actinomycosis accounts for an estimated 10% of all cases.

What causes actinomycosis?

Actinomycosis is caused by a family of bacteria known as actinomycetaceae. In most cases, the bacteria live harmlessly on the lining of the mouth, throat, digestive system and vagina (in women).

The bacteria only pose a problem if the tissue lining becomes damaged by injury or disease, allowing the bacteria to penetrate deeper into the body.

This is potentially serious because these are anaerobic bacteria, which means they thrive in parts of the body where there isn’t much oxygen, such as deep inside body tissues.

However, an advantage of actinomyces bacteria being anaerobic is that they can’t survive outside the human body. This means that actinomycosis isn’t a contagious condition.

Read more about the causes of actinomycosis.

Diagnosing actinomycosis

Actinomycosis can be difficult to diagnose in its early stages and is often only discovered during tests or surgery to check for other conditions.

For example, many cases of actinomycosis are detected when a biopsy (tissue sample removal) is carried out to check for cancer.

Read more about how actinomycosis is diagnosed.

Treating actinomycosis

Actinomycosis usually responds well to treatment, which involves taking a long-term course of antibiotics.

The course usually lasts several months to ensure all the bacteria are killed.

In some cases, minor surgery may be required to repair the damaged tissue and drain pus out of the abscesses.

Read more about how actinomycosis is treated.

Complications of actinomycosis

Abscesses that develop as a result of actinomycosis may form in many parts of your body, including your lungs. They can spread easily from one part of your body to another.

If the original site of the infection is located in the skin of your face, it may spread to nearby parts of your body, such as your scalp or ears.

If the original site of the infection is your mouth, it may spread to your tongue, larynx (voicebox), trachea (windpipe) and salivary glands, and the tubes that connect your throat to your nose.

If the infection spreads to your brain, a brain abscess could develop.

Preventing actinomycosis

Most cases of oral actinomycosis occur as a result of poor dental hygiene. This means practising good dental hygiene is the best way to prevent actinomycosis.

Read about preventing tooth decay and dental health for more information and advice about good oral hygiene practices.

There are four main types of actinomycosis. Symptoms will vary depending on which type you have.

The symptoms of each type are described below.

Oral cervicofacial actinomycosis

The symptoms of oral cervicofacial actinomycosis include:

• swollen lumps on your cheek or neck, which can gradually increase in size and number
• reddish or bluish-coloured skin over the lumps
• a high temperature (fever) of 38C (100.4F) or above may also occasionally develop

During the initial stages of oral cervicofacial actinomycosis, the lumps may be tender before later becoming painless and hard to the touch. Your jaw muscles may also be affected, which can make chewing difficult.

Oral cervicofacial actinomycosis can also cause narrow passages called sinus tracts to open in the surface of your skin in the affected areas. These shouldn’t be confused with sinuses, which are the cavities in your face and nose.

The sinus tracts leak pus, which may contain a yellow, granular, lumpy material.

Thoracic actinomycosis

The symptoms of thoracic actinomycosis may include:

• a high temperature (fever) of 38C (100.4F) or above
• weight loss
• tiredness (fatigue)
• loss of appetite
• shortness of breath 
• chest pain
• the appearance of sinus tracts on the surface of your chest

You may also develop a dry cough or a cough that produces phlegm. You may bring up drops of blood when you cough, or if you produce phlegm it may be bloodstained.

Abdominal actinomycosis

The symptoms of abdominal actinomycosis may include:

• mild fever – usually a temperature that’s no higher than 38C (100.4F)
• weight loss
• tiredness (fatigue)
• a change in your bowel habits, such as constipation or diarrhoea
• abdominal (tummy) pain
• nausea and vomiting
• a noticeable mass or lump in your lower abdomen
• the appearance of sinus tracts on the surface of your abdomen

Pelvic actinomycosis

The symptoms of pelvic actinomycosis may include:

• lower abdominal pain
• irregular or abnormal vaginal bleeding or vaginal discharge
• loss of appetite
• tiredness (fatigue)
• mild fever
• a noticeable mass or lump in your pelvis

Antibiotics are the main treatment for actinomycosis. A long-term course of antibiotics is required to wipe out the infection completely.

An initial course of antibiotic injections is usually recommended for 2 to 6 weeks, followed by antibiotic tablets for another 6 to 12 months.

A nurse should be able to teach you how to administer antibiotic injections at home so you don’t need to stay in hospital for the duration of the course.

The preferred antibiotics for treating actinomycosis are benzylpenicillin, which is used for the antibiotic injections, and amoxicillin tablets.

In some cases, other bacteria are also present and more than one antibiotic or other antibiotics will need to be given.

Side effects of these antibiotics include:

• diarrhoea 
• nausea (feeling sick)
• skin rash
• increased vulnerability to fungal infections, such as oral thrush (a fungal infection that occurs in the mouth)

If you’re allergic to penicillin, alternative antibiotics such as tetracycline or erythromycin can be used.

Read more about antibiotics.

Surgery

Surgery may occasionally be needed to repair tissue damage or drain pus from any abscesses that have formed deep inside your body.

Intrauterine device (IUD)

If you experience symptoms of pelvic actinomycosis caused by an intrauterine device (IUD), such as lower abdominal pain or irregular or abnormal vaginal bleeding or discharge, the IUD will need to be removed.