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Anaerobic Infections

Understanding anaerobic infections

Anaerobic infections are common infections caused by anaerobic bacteria. These bacteria occur naturally and are the most common flora in the body. In their natural state, they don’t cause infection. But they can cause infections after an injury or trauma to the body. Anaerobic infections commonly affect the:

  • abdomen
  • genitals
  • heart
  • bones
  • joints
  • central nervous system
  • respiratory tract
  • skin
  • mouth

These infections can be difficult to treat. Common anaerobic infections include:


Anaerobic infections can happen when deep tissues become injured or exposed. This can occur due to trauma or surgery, such as animal bites or root canals.

Your risk is higher if you have:

  • low blood supply
  • staph infection
  • open wounds, which can easily become infected
  • diabetes
  • a weak immune system

HIV, AIDS, or any condition that severely weakens the immune system can increase your risk of periodontitis and related conditions involving inflammation in your mouth and gums. Certain other conditions can also make you more prone to anaerobic infections, including:

  • carcinoma in the lungs, uterus, or colon
  • neutropenic colitis, a complication of chemotherapy that that affects the colon
  • leukemia


Common symptoms of an anaerobic infection include:

  • noticeable infection near the skin
  • smelly discharge
  • pus-filled abscess
  • tissue damage or gangrene
  • discoloration of the infected area

Infection in the mouth or throat can also cause tender gums, bad breath, or pain. Infection in the lungs can also cause chest pain or coughing. And infection of the skin can also cause pain, redness, or swelling.

Diagnosing anaerobic infections

Your doctor first performs a physical exam to diagnose an anaerobic infection. Testing a sample of the infected tissue can help your doctor identify the infecting bacteria. X-rays or imaging scans may be needed for internal infections. Your doctor will also ask about your symptoms.

Treating anaerobic infections

Drug treatment

Anaerobic infections are usually treated with antibiotics and other medications. The antibiotic you receive depends on the type of infection you have and the bacteria that likely caused it. For infections in your mouth, throat, or lungs, your doctor may give you:

If you have an infection in your gastrointestinal (GI) tract or your pelvic area, which is most common in women, your doctor may give you:

Once your doctor has identified the bacteria, they’ll prescribe you the medication or combination of medications you need.


Drainage of pus is also necessary to treat the infection. The infection or abscess may need to be surgically removed in some cases. This is known as debridement, the removal of unhealthy tissue from a wound.

Then, your doctor will make sure that blood is circulating normally to the area. They will look for anything blocking your tissues from healing. They will also monitor the area until it’s free of infectious bacteria and functioning normally.

Preventing anaerobic infections

See your doctor as soon as you notice symptoms of an infection anywhere on or inside your body. Getting treatment for minor infections can help prevent the spread of bacteria.

Anaerobic infections in the lungs and mouth can be prevented in a variety of ways, including:

  • maintaining excellent oral hygiene, such as brushing and flossing twice a day
  • having any infectious fluids in your mouth suctioned out by your dentist
  • keeping your stomach acid pH level balanced

You can help prevent anaerobic infections on your skin and soft tissues by taking proper care of cuts as soon as they occur.

Your doctor may also give you antibiotics before surgery to prevent bacteria from infecting your blood. Taking a drug before surgery also prevents any anaerobic infections from occurring around the area being operated on.


Untreated anaerobic infections can lead to other serious conditions, including:

Many of these conditions have their own set of symptoms and complications, including tooth loss, fever, fatigue, organ failure, and, in some cases, death.


Anaerobic infections can be life-threatening if not treated properly and quickly. Diagnosing this type of infection can take a few days or more. After diagnosis, your doctor will likely give you antibiotics.

Some factors can increase your risk of complications, such as:

  • age
  • underlying conditions involving the heart, liver, or kidneys
  • polymicrobial infections, in which multiple types of organisms (including viruses, parasites, and fungi) cause infection

One study showed that old age and liver disease especially increased the risk of complications.

However, a complete recovery is likely following proper and early treatment. The earlier you see your doctor when you start noticing symptoms, the more likely you’ll be able to fight off the anaerobic infection.

Content licensed from:

Written by: Amber Erickson Gabbey and Tim Jewell
Medically reviewed on: Oct 13, 2016: Deborah Weatherspoon, PhD, RN, CRNA, COI

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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