People with very weak immune (body defense) systems are at risk for getting nocardiosis.

Several diseases and conditions can cause the immune system to be weak. These include:

• Diabetes
• Cancer
• HIV/AIDS
• Pulmonary alveolar proteinosis (an illness that causes the air sacs of the lungs to become plugged)
• Connective tissue disorder (a disease that affects the tissue that connects and supports different parts of the body)
• Alcoholism
• Having a bone marrow or solid organ transplant
• Taking high doses of drugs called corticosteroids

In the United States, it has been estimated that 500-1,000 new cases of nocardiosis infection occur every year. Approximately 60% of nocardiosis cases are associated with pre-existing immune compromise.

In addition, men have a greater risk of getting the infection than women; for every female who gets sick with nocardiosis, there are about 3 males who get the disease.

Nocardiosis is a disease caused by a type of bacteria that is found in the environment, typically in standing water, decaying plants, and soil. These bacterial species belong to the genus Nocardia giving the disease its name. Nocardia and other related bacteria are considered to be opportunistic pathogens. These are bacteria that infect humans and animals when the conditions are right. They can cause severe infections in people with weakened immune systems who have difficulty fighting off infections (for example, people with cancer or those taking certain medications such as steroids).

Infection often happens:

• When someone breaths in dust that contains the bacteria (lung infection)
• When soil or water carrying nocardiosis bacteria gets into the skin through a cut or scrape (traumatic inoculation)
• When a hospitalized patient is infected from contaminated medical equipment or from bacteria getting into a wound after surgery (hospital-acquired infection)

Nocardiosis can show up in the body as a skin or lung infection or as an infection that has spread throughout the body (disseminated infection).

In the United States, nocardiosis most often shows up as a lung infection. In all cases, if the disease is left untreated, it can spread to other parts of the body, including the spinal cord and the brain. The brain is the most common site of disseminated infection. Up to 44% of all people with infection in the brain or spinal cord die. The risk for death is much higher for patients with very weak immune systems—more than 85% of them die after developing nocardiosis of the brain or spinal cord.

The symptoms of nocardiosis vary depending on which part of your body is affected.

Nocardiosis most commonly occurs in the lungs. If your lungs are infected, you can experience:

• Fever
• Weight loss
• Night sweats
• Cough
• Chest pain
• Pneumonia

When lung infections occur, the infection can spread to the brain. If your central nervous system (brain and spinal cord) is infected, you can experience:

• Headache
• Weakness
• Confusion
• Seizures

Skin infections can occur when soil containing Nocardia species gets into open wounds or cuts. Farming or gardening without gloves and protective clothing increases the risk of cuts, thorn pricks, or other minor injuries. If your skin is infected, you can develop:

• Skin ulcers (shallow wound on the surface of the skin)
• Nodules, sometimes draining, with the infection spreading along lymph nodes

Talk to your doctor if you have an injury that won’t heal and are experiencing any of the signs and symptoms listed. You should also tell your doctor how you were wounded because that information may improve your chances for getting a correct diagnosis and appropriate treatment.

Diagnosis

Your doctor can help you find out if you have the disease by performing tests that can identify the bacteria that cause nocardiosis.
To conduct these tests, the doctor may need to take samples from the area of your body that is infected. For example:

• Lungs (or other parts of the lower airways)
• Mucus from the lower airways
• Skin
• Brain tissue

Treatment

People with nocardiosis may need to take multiple antibiotics given for several months—or even up to a year or more. Treatments are sometimes given for a long time to prevent symptoms from returning. Sometimes abscesses or wound infections need to be surgically drained.

Because some Nocardia species are resistant to certain antibiotics, laboratory testing is needed to find out which species is causing the infection. Your doctor might run tests to find out which antibiotics the bacteria are resistant to so that you are given a treatment that will stop your infection.

Talk with your doctor about the best treatment for you.

Nocardiosis is typically treated with the use of antibiotics. Because some Nocardia species are resistant to certain antibiotics, laboratory testing is needed to find out which species is causing the infection and to which antibiotic these bacteria may be susceptible. Treatment usually lasts for at least six months and may involve use of more than one antibiotic, but depending on the severity may last for about a year. Some abscesses or wound infections may need to be surgically drained.

The antibiotic known as trimethoprim-sulfamethoxazole (TMP-SMZ) is considered the therapy of choice by most doctors. Other antibiotics include:

• Sulfonamides
• Carbapenems (imipenem or meropenem, but not ertapenem)
• Third-generation cephalosporins (cefotaxime or ceftriaxone), and amikacin, alone or in combination.
• Imipenem plus amikacin (which may be the chosen treatment for patients with sulfonamide-allergic patients)
• Linezolid
• Tigecycline
• Combination therapy with several antibiotics

Other alternative oral treatment include minocycline and amoxicillin/clavulanate, in addition to linezolid.

There are no specific ways to prevent infection. People who have weakened immune systems should wear shoes as well as clothing covering the skin, open wounds, and cuts when they are working in the soil. This could prevent skin infections.

People who have an organ transplant might be given antibiotics to prevent bacterial infections. Some studies have shown that this might prevent nocardiosis.

Outbreaks of nocardiosis in hospitals are rare. A few outbreaks have been linked to other patients, healthcare workers, and the release of bacteria in the air during hospital construction work. Hospitals should maintain strong infection control practices to avoid outbreaks of nocardiosis.