Nocardiosis
Nocardiosis
Disease History, Characteristics, and Transmission
Introduction
Nocardiosis is a serious infectious disease with a high mortality (death) rate. It is caused by funguslike bacteria that affect the lungs (pulmonary nocardiosis), skin (nocardiosis), or the entire body (disseminated or systemic nocardiosis), especially the brain and meninges. According to the U.S. Centers for Disease Control and Prevention (CDC), the majority of cases—about 80%— involves lung infections, brain abscesses, or disseminated (widespread) diseases. The other 20% of cases involve the skin. With respect to cures, when the skin and soft tissues are involved, cure rates are about 100%; when the lungs are involved, the cure rate is about 90% of the cases; disseminated cases are cured about 63% of the time; and when the brain is involved, the cure rate drops to 50% These cure rates are only achieved when proper therapy is given in a timely manner.
The infection itself is caused by bacteria of the genus Nocardia. At least 15 species have so far been identified, with new species still being found. The bacteria that cause infection the most frequently are: Nocardia astreoides and Nocardia brasiliensis. However, N. farcinica, N. nova, N. transvalensis, and N. pseudobrasiliensis also cause infection. N. astreoides is responsible for about 50% of all invasive cases, and is the species responsible for the most cases of nocardiosis in the United States.
Disease History, Characteristics, and Transmission
Nocardia are often found in soil and dust particles. They cause occasional disease in humans and animals around the world. Transmission of pulmonary nocardiosis is usually accomplished by inhalation of the organisms when they are within airborne dust particles. Transmission of systemic nocardiosis usually occurs by direct contact with soil through puncture wounds. Abrasions (scrapes) can also be a route for transmission, but less frequently than the other two means. There are no known cases of human-to-human transmission of Nocardia. The incubation period is not known, however, it is suspected to be several weeks.
Symptoms of the pulmonary form are usually chills, fever, cough (similar to pneumonia or tuberculosis), thick (often bloody) sputum, night sweats, and chest pain. When the bacteria affect the brain, symptoms usually include severe headaches, lethargy, disorientation, confusion, dizziness, nausea and seizures, problems with walking, and sudden neurological problems. These symptoms are often more severe in patients with compromised immune systems. If a brain abscess (localized area of infection) ruptures, the infection can often lead to meningitis (infection of the outer covering of the brain, or meninges). When the skin is affected, rashes, lumps, and sores are usually present, along with swollen lymph nodes. They are often located in the skin or directly underneath the skin. Lesions may also form in the kidneys, liver, and bones.
WORDS TO KNOW
CUTANEOUS: Pertaining to the skin.
IMMUNOCOMPROMISED: A reduction of the ability of the immune system to recognize and respond to the presence of foreign material.
MORTALITY: Mortality is the condition of being susceptible to death. The term “mortality” comes from the Latin word mors, which means “death.” Mortality can also refer to the rate of deaths caused by an illness or injury, i.e., “Rabies has a high mortality.”
SYSTEMIC: Any medical condition that affects the whole body (i.e., the whole system) is systemic.
Scope and Distribution
Nocardiosis is found throughout the world. People of all ages can contract the infection, although it occurs more frequently in people 40–49 years of age. Nocardiosis is more common in males than females by a three to one ratio. It is especially common in people with impaired immune systems and people who have chronic lung problems, such as emphysema.
About 0.4 cases occur in 100,000 people in the United States. According to the CDC, about 500– 1,000 new cases are reported annually. No accurate statistics are available internationally. People with lowered immune systems are especially vulnerable; however, people with no history of serious diseases can also get the disease. It cannot be transmitted from person to person.
Immunocompromised persons are at increased risk from Nocardia. This risk includes such groups as people with cancer, connective tissue disorders, bone marrow transplants, solid organ transplants, high-dose cortico-steroid use, and HIV/AIDS (human immunodeficiency virus/acquired immunodeficiency syndrome).
Treatment and Prevention
The diagnosis is sometimes difficult because Nocardia grow more slowly than most bacteria, and so cultures are often not analyzed for a sufficient amount of time in the clinical laboratory. In addition, the infection inside cultures of sputum or discharge is not easily identifiable. It is most often identified from respiratory secretions, abscess aspirates, and skin biopsies. Physicians also use special staining techniques. In addition, they take a complete medical history to help evaluate the patient. Lung biopsies and chest x rays are also sometimes taken. For brain infections, computer tomography (CT) or magnetic resonance imaging (MRI) scans are usually used.
A treatment usually lasts at least six months, but sometimes 12–18 months or longer is needed to cure the infection. Bed rest is recommended during antibiotic drug treatment. Short-term antibiotic treatment does not work. Sometimes, co-trimoxazole or sulfonamide drugs (in high doses) are used. Sulfadiazine is often used. The combination of trimethoprim-sulfamethoxazole (TMP-SMX) is generally the drug treatment preferred by the medical community. If patients do not respond to these medicines, ampicillin, erythromycin, or minocycline may be added to them.
Recently, according to the CDC Division of Bacterial and Mycotic Diseases, the drug combination of sulfonamide, ceftriaxone, and amikacin has shown promising results, especially when TMP-SMX is difficult to administer. Treatment sometimes also includes surgery to excise dead tissue and drain abscesses. Bed rest is recommended while the patient recovers, however, activity may slowly resume. Sometimes with chronic cases, a therapy called chronic suppressive therapy is used that includes prolonged, low-dose antibiotic therapy. The prognosis is best for the patient when nocardiosis is diagnosed early and before it reaches the brain.
Diagnosis has been difficult in the past. However, new diagnostic tools, including molecular diagnostic and subtyping methods, are helping to better identify the infection.
Impacts and Issues
Nocardia infections are difficult for physicians because they cause a wide variety of diseases, especially in immunocompromised patients, that require extra expertise. The number of cases has been increasing. However, this increase in numbers is generally attributed to improvements in diagnostic techniques and to the overall increase in the number of severely immunocompromised persons throughout the world.
Recovery may be slow. Treatments are usually able to control the infection. Sometimes, allergies to the antibiotics prescribed to treat the infection occur, and alternatives may need to be provided. The prognosis is generally good when the diagnosis and treatment are prompt and on target. However, the outcome is generally poor after the infection has spread widely in the body, and treatment has not been prompt. Three of the major complications are rib lesions, brain abscesses, and skin infections.
IN CONTEXT: TRENDS AND STATISTICS
The Division of Bacterial and Mycotic Diseases at Centers for Disease Control and Prevention (CDC) estimates that “500 to 1,000 new cases of Nocardia infection occur annually. An estimated 10% to 15% of these patients also have HIV infection.”
SOURCE: Centers for Disease Control and Prevention (CDC), Coordinating Center for Infectious Diseases, Division of Bacterial and Mycotic Diseases.
See AlsoAntibacterial Drugs; Bacterial Disease; CDC (Centers for Disease Control and Prevention).
BIBLIOGRAPHY
Books
Handbook of Diseases. 3rd ed. Philadelphia: Lippincott Williams & Wilkins, 2004.
Web Sites
Centers for Disease Control and Prevention. “Nocardiosis.” October 13, 2005. <http://www.cdc.gov/ncidod/dbmd/diseaseinfo/nocardiosis_t.htm> (accessed March 15, 2007).
Nocardiosis
Nocardiosis
Definition
Nocardiosis is a serious infection caused by a fungus-like bacterium that begins in the lungs and can spread to the brain.
Description
Nocardiosis is found throughout the world among people of all ages, although it is most common in older people and males. While people with poor immunity are vulnerable to this infection, it sometimes strikes individuals with no history of other diseases. Nocardiosis is rare in AIDS patients. It is not transmitted by person-to-person contact.
Causes and symptoms
Nocardiosis is caused by a bacterium of the Nocardia species—usually N. asteroides, an organism that is normally found in the soil. The incubation period is not known, but is probably several weeks.
The bacteria can enter the human body when a person inhales contaminated dust. Less often, people can pick up the bacteria in contaminated puncture wounds or cuts.
Symptoms
The infection causes a cough similar to pneumonia or tuberculosis, producing thick, sometimes bloody, sputum. Other symptoms include chills, night sweats, chest pain, weakness, loss of appetite and weight loss. Nocardiosis does not, however, respond to short-term antibiotics.
Complications
In about one-third of patients, the infection spreads from the blood into the brain, causing brain abscesses. This complication can trigger a range of symptoms including severe headache, confusion, disorientation, dizziness, nausea and seizures, and problems in walking. If a brain abscess ruptures, it can lead to meningitis.
About a third of patients with nocardiosis also have abscesses in the skin or directly underneath the skin. They may also have lesions in other organs, such as the kidneys, liver, or bones.
Diagnosis
Nocardia is not easily identified from cultures of sputum or discharge. A doctor can diagnose the condition using special staining techniques and taking a thorough medical history. Lung biopsies or x rays also may be required. Up to 40% of the time, however, a diagnosis can't be made until an autopsy is done.
Treatment
Treatment of nocardiosis includes bed rest and high doses of medication for a period of 12 to 18 months, including sulfonamide drugs or a combination of trimethoprim-sulfamethoxazole (Bactrim, Septra). If the patient doesn't respond to these drugs, antibiotics such as ampicillin (Amcill, Principen) or erythromycin (E-Mycin, Eryc) may be tried.
The abscesses may need to be drained and dead tissue cut away. Other symptoms are treated as necessary.
Prognosis
Nocardiosis is a serious disease with a high mortality rate. If it has been diagnosed early and caught before spreading to the brain, the prognosis is better. Even with appropriate treatment, however, the death rate is still 50%. Once the infection reaches the brain, the death rate is above 80%. This outcome is most commonly seen in patients with a weakened immune system.
KEY TERMS
Abscess— A localized area of infection in a body tissue. Abscesses in the brain or skin are possible complications of nocardiosis.
Meningitis— An infection of the outer covering of the brain (meninges) that can be caused by either bacteria or a virus.
Resources
BOOKS
Orris, June, editor. Handbook of Diseases. Springhouse, PA: Springhouse Corp., 1996.