Nocardiosis

• Infections caused by bacteria of the genus Nocardia.
• It can affect the lungs, brain, and skin.

It is most common in people with weakened immune systems who have difficulty fighting off infections. Antibiotic treatment might be given for several months to get rid of the infection.

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Nocardiosis

Etiologic Agent of Nocardiosis

• The most commonly reported species from clinical sources are:

• Nocardia nova
• Nocardia farcinica
• Nocardia cyriacigeorgica
• Nocardia brasiliensis
• Nocardia abscessus
• More than 40 valid Nocardia species are considered clinically relevant.

Risk of infection

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:

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Nocardiosis - Gram stain

• 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.

Signs and Symptoms

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

Nocardiosis nodules

Transmission

• 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.

Nocardiosis

Laboratory Diagnostics

• Infections due to Nocardia species are often overlooked due to the extended incubation time needed to isolate the organism from primary clinical specimens. Routine cultures must be held for at least 14 days. Accurate identification of Nocardia species recovered requires molecular methods. Referral of isolates to a reference laboratory, such as CDC’s Special Bacteriology Reference Laboratory, may be needed for identification and Antimicrobial Susceptibility Testing.

Treatment

• Some nocardiae are reported to have species-specific susceptibility profiles, but multidrug-resistant strains are common. Because of this, antimicrobial susceptibility testing (AST) should be performed on every isolate of clinical significance.

• N. farcinica is often resistant to multiple antimicrobial agents, including trimethoprim-sulfamethoxazole (TMP-SMX), and has been shown to be more virulent in an animal model. TMP-SMX therapy for HIV-infected patients may be complicated by frequent occurrence of adverse events and drug resistance.

Prevention

• 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.

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