Nocardiosis
Nocardiosis is a respiratory infection caused by the bacterium Nocardia, which is commonly found in soil, sand, and water globally. While exposure to Nocardia is widespread, infections primarily affect individuals with compromised immune systems, such as those living with AIDS or undergoing immunosuppressive treatments. The infection often manifests as pneumonia or lung abscesses, and can potentially spread to other organs, including the brain and skin, leading to more severe conditions. Symptoms of nocardiosis may include shortness of breath, productive cough, weight loss, fever, and in some cases, coughing up blood. Diagnosis typically involves a thorough physical examination coupled with various imaging and laboratory tests. Treatment generally requires an extended course of antibiotics, particularly sulfonamides, and may necessitate supportive care and surgical intervention for abscesses. Although no specific preventive measures exist, nocardiosis is relatively rare among individuals with intact immune systems. Understanding nocardiosis is crucial for those at risk, as timely diagnosis and appropriate treatment can significantly improve outcomes.
Nocardiosis
- ANATOMY OR SYSTEM AFFECTED: Lungs, respiratory system, skin, brain, central nervous system
Definition
Nocardiosis is a respiratory infection caused by the bacterium Nocardia, which lives in soil, sand, and water worldwide. Nocardiosis can also affect the brain, skin, and central nervous system. Although exposure to Nocardia is widespread, infection primarily occurs in people with compromised immunity, such as persons with acquired immunodeficiency syndrome (AIDS).
Causes
N. asteroides is one of the members of the Nocardia species associated with causing infection in humans. Nocardiosis is believed to occur when airborne microbes are inhaled and then colonize the lungs. Infection typically manifests with pneumonia or with the formation of a lung abscess or pus-filled cavity (empyema), or both. Immunocompromised people are susceptible to infection spread by way of the bloodstream from the lungs to other organs, such as the heart and adjacent tissues, the brain, skin, bone, and kidneys. In some people, infection is limited to areas outside the lungs (extrapulmonary nocardiosis), while in others, the infection becomes widespread (disseminated nocardiosis).
Risk Factors
The risk for nocardiosis is increased by any physical condition that results in an impaired immune system. These conditions include AIDS or human immunodeficiency virus (HIV) infection, lowered immunity from the use of medications (such as corticosteroids and chemotherapy), having undergone organ or bone marrow transplantation, and having a serious chronic illness, such as liver disease or lupus. Chronic lung disease also increases the risk for nocardiosis because the diseased lungs are compromised and unable to fight infection.
Symptoms
Nocardiosis that affects the lungs can result in symptoms that include shortness of breath, a productive cough, weight loss, a fever, and coughing up blood (hemoptysis). Other symptoms depend upon the location of the infection, but can affect the gastrointestinal system, muscles and joints, the skin, and the nervous system.
Screening and Diagnosis
A complete physical exam and medical history will be completed, together with diagnostic tests that will be used to distinguish the symptoms of nocardiosis from those of other diseases. Tests include bacterial cultures of blood and sputum; chest X-ray; computed tomography (CT) scan; magnetic resonance imaging (MRI) scan of involved organs (chest and head); thoracentesis, which involves drainage of fluid from the lung; and less often, a lumbar puncture, a procedure in which a needle is used to aspirate cerebrospinal fluid for analysis to identify infection of the central nervous system.
Treatment and Therapy
Treatment may be administered in an intensive care setting, especially for persons with widespread infection. Nocardiosis is treated with an extended course of antibiotic therapy. A class of antibiotics called sulfonamides is effective in eradicating Nocardia, but alternative antibiotics may be used. A combination of antibiotics, including imipenem, amikacin, trimethoprim-sulfamethoxazole ceftriaxone, linezolid, and minocycline, is often necessary. Affected persons may also receive supportive treatments such as medications for fever and pain and supplemental oxygen. Surgical drainage of an abscess may also be necessary.
Prevention and Outcomes
Exposure to Nocardia cannot be avoided; as such, there is no specific method of prevention of nocardiosis. Nocardiosis, however, is uncommon in people of average or better health.
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