Nocardia Pneumonia - Causes, Symptoms, Diagnosis, and Management

Introduction:

Nocardia pneumonia, otherwise called pulmonary nocardiosis or nocardiosis, is caused by the bacteria Nocardia asteroids. These bacteria can be found both in soil and water. It is a gram-positive Bacillus presenting with branching filamentous forms and belongs to the aerobic actinomycetes group. It is an infectious disease associated with pulmonary manifestations. The infection can spread through other organs through the bloodstream. Pulmonary nocardiosis cases are reported worldwide. Males are more commonly affected than females. The infection is more common in older adults. About 500 to 1000 new cases are reported in the United States of America every year.

What Are the Causes of Nocardia Pneumonia?

• The causative organism responsible for causing the infection is Nocardia asteroids, found in the soil.

• The microorganisms are carried into the air, and when a person inhales the bacteria, it reaches the lungs and causes pulmonary problems. Rarely, the organism may enter the body through other routes, such as skin or the gastrointestinal tract.

• Other species of the bacteria, such as Nocardia caviae, Nocardia farcinica, and Nocardia brasiliensis, are also involved in causing the disease.

• Immunocompromised (immunity low or immune system not functioning properly) people are at increased risk for pulmonary nocardiosis.

• People who are taking immunosuppressants routinely for organ transplantation are more susceptible to this kind of infection.

• Certain medical conditions such as Cushing's disease, lymphoma, and chronic lung problems caused due to emphysema, smoking, or tuberculosis are at greater risk of contracting the infection.

What Are the Signs and Symptoms of Nocardia Pneumonia?

The symptoms are mostly similar to the symptoms of tuberculosis and pneumonia.

Various signs and symptoms may include-

Pulmonary (lung) manifestations include:

• Lung abscess with cavitary lesions is one of the common symptoms.

• Cough (with blood or mucus).

• Bloody sputum.

• Chest pain.

• Difficulty in breathing.

• Rapid breathing.

• Shortness of breath.

Generalized symptoms include:

• Night sweats.

• Chills.

• Fever.

• Generalized weakness.

• Weight loss (unintentional).

• Lack of appetite.

• Joint pain.

• Nausea.

• Vomiting.

Nervous system symptoms include:

• Severe headache.

• Confusion.

• Dizziness.

• Seizures.

• Vision changes.

• Altered mental state.

• Confusion.

Skin manifestations include:

• Skin sores.

• Skin abscess.

• Swollen lymph nodes.

• Rashes or lumps in the skin.

What Are the Organs Involved and How Does It Spread?

• The organism may travel through the bloodstream to other parts and cause various complications.

• It reaches the brain and may result in the formation of brain abscesses associated with sensory, motor, and focal disturbances and severe headaches.

• If the skin is involved, the infection manifests with skin abscesses, usually on the buttocks, hand, and chest wall. It reports approximately one-third of all nocardiosis cases.

• The rate of disease progression increases very rapidly in people suffering from ulcerative colitis, malignancy of the lymphatic system, affected with acquired immunodeficiency syndrome (AIDS) virus, or in patients taking cytotoxic or corticosteroids.

• The duration of infection may last for several months to years.

What Are the Possible Complications?

Some of the complications associated with Nocardia infections include-

• Kidney infections.

• Brain abscess.

• Skin infections.

What Is the Prognosis of This Condition?

Generally, the prognosis is good if the disease is diagnosed and treated earlier. The outcome is limited or poor in certain conditions, such as-

• If treatment is delayed.

• If the infection spreads to other organs from the lungs.

• People taking long-term immunosuppressants for other serious disorders present.

How Is It Diagnosed?

Laboratory Examination-

• The laboratory test is carried out with microscopic examination and culture.

• Polymerase Chain Reaction Test- It is the most simple and accurate test done along with 16S rDNA sequencing.

• Modified acid-fast staining with one percent sulphuric acid (decolorizer) is used to identify the Nocardia organisms microscopically, which shows the presence of pink-colored Filamentous bacilli.

• Nocardia asteroides are identified well on the Lowenstein-Jensen’s medium (LJ medium) when it is incubated between the temperature of 30 degrees Celsius and 37 degrees Celsius.

• The other species of Nocardia grows well on the blood agar and Saboraud’s dextrose agar (SDA).

• The chances of better isolation are seen in the cases of culture, which include agar medium enriched with yeast extract (BCYEA- buffered charcoal yeast extract agar).

• After 48 hours of incubation, colonies of Nocardia species start to appear; however, the growth may be visible after one week in the case of some species.

• If plates are discarded after 48 hours, as practiced in several parts of the world, the laboratories may end up with negative results.

• The molecular method is highly recommended to be used along with multi-locus sequence analysis (MLSA) in the identification of suspected human Nocardia species.

• This method is effective as it minimizes underreporting and the chances of misdiagnosis.

• Reports suggest the importance of presumptive clinical diagnosis of Nocardia species from the improvement of laboratory isolation from the clinical samples observed.

How Is It Treated?

• The Nocardia species organisms are more sensitive to most of the Penicillin and Cephalosporin antibiotic groups.

• Linezolid, Ampicillin, Erythromycin, and Minocycline are the antibiotics that are effectively used against gram-positive bacteria used in the treatment of pulmonary nocardiosis infection.

• A combination of Sulfonamides (Trimethoprim or Sulfamethoxazole), Ceftriaxone, and Amikacin are used in the treatment of human nocardiosis.

• As reports suggest, around 50 % of the patients are resistant to Trimethoprim or Sulfamethoxazole (TMP/SMX).

• This gives emergence to the combination of new drugs such as Ceftriaxone and Imipenem as an alternative to Trimethoprim and Sulfamethoxazole.

Conclusion:

Nocardia pneumonia is one of the primary causes of mortality and morbidity in immunocompromised patients. It is a bacterial infection with a high probability of misdiagnosis as the symptoms are similar to pneumonia and tuberculosis. A clear understanding and knowledge of the disease courses, predisposing factors, and symptoms help in planning the treatment of this fatal condition. To prevent misdiagnosis, clinicians, microbiologists, and chest disease specialists should consider and evaluate the possibility of human nocardiosis. Standard protocols should be followed properly in the clinical and microbiology laboratories while carrying out sputum cultures. There are no reported cases of human-to-human transmissions.