Nocardiosis - Causes, Symptoms and Treatments
Nocardiosis is an acute, subacute, or chronic bacterial infection caused by a weakly grampositive species of the genus Nocardia - usually N. asteroides. It is most common in men, especially those with a compromised immune system. In patients with brain infection, mortality exceeds 80%; in other forms, mortality is 50%, even with appropriate therapy.
Causes of Nocardiosis:
Nocardia are aerobic gram-positive bacteria with branching filaments similar in appearance to fungi. Normally found in soil, these microbes cause occasional sporadic disease in humans and animals throughout the world. Their incubation period is unknown but is probably several weeks. The usual mode of transmission is inhalation or organisms suspended in dust. Transmission by direct inoculation through puncture wounds or abrasions is less common.
Signs and symptoms of Nocardiosis:
Nocardiosis originates as a pulmonary infection with a cough that produces thick, tenacious, purulent, mucopurulent, and possibly blood-tinged sputum. It may also cause a fever as high as 105° F (40.6° C), chills, night sweats, anorexia, malaise, and weight loss. This infection may lead to pleurisy, intrapleural effusions, and empyema. Other effects include tracheitis, bronchitis, pericarditis, endocarditis, peritonitis, mediastinitis, septic arthritis, and keratoconjunctivitis. If the infection spreads through the blood to the brain, abscesses form, causing confusion, disorientation, dizziness, headache, nausea, and seizures. Rupture of a brain abscess can cause purulent meningitis. Extrapulmonary, hematogenous spread may cause endocarditis and lesions in the kidneys, liver, subcutaneous tissue, and bone.
Diagnosis for Nocardiosis:
Identifying Nocardia by culture of sputum or discharge is difficult. In many cases, special staining techniques must be used to make the diagnosis, in conjunction with a typical clinical picture (usually progressive pneumonia, despite antibiotic therapy). Occasionally, diagnosis requires biopsy of lung or other tissue. Chest X -rays vary and may show fluffy or interstitial infiltrates, nodules, or abscesses. Unfortunately, up to 40% of nocardial infections elude diagnosis until postmortem examination.
In brain infection with meningitis, lumbar puncture shows nonspecific changes, such as increased opening pressure; cerebrospinal fluid with increased white blood cell and protein levels; and decreased glucose levels compared to serum glucose.
Treatment of Nocardiosis:
Nocardiosis requires 12 to 18 months of treatment, preferably with co-trimoxazole or high doses of sulfonamides. In patients who do not respond to sulfonamide treatment, other drugs, such as ampicillin, erythromycin, or minocycline, may be added. Treatment also includes surgical drainage of abscesses and excision drainage of abcesses and excision of necrotic tissue. The acute phase requires complete bed rest; as the patient improves, activity can increase.
Special considerations for Nocardiosis:
Because it is not transmitted from person to person, nocardiosis requires no isolation.
1. Provide adequate nourishment through total parenteral nutrition, nasogastric tube feedings, or a balanced diet.
2. Give the patient tepid sponge baths and antipyretics, as ordered, to reduce his fever.
3. Monitor for allergic reactions to antibiotics.
4. High-dose sulfonamide therapy (especially sulfadiazine) predisposes the patient to crystalluria and oliguria, so assess him frequently, force fluids, and alkalinize the urine with sodium bicarbonate, as ordered, to prevent these complications.
5. In patients with pulmonary infection, administer chest physiotherapy. Auscultate the lungs daily, checking for increased crackles or consolidation. Note and record the amount, color, and thickness of sputum.
6. In brain infection, regularly assess neurologic function. Watch for signs of increased intracranial pressure, such as decreased level of consciousness, and respiratory abnormalities.
7. In long-term hospitalization, turn the patient often, and assist with range-of-motion exercises.
8. Before the patient is discharged, stress the need to follow a regular medication schedule to maintain therapeutic blood levels, and to continue drugs even after symptoms subside. Explain the importance of frequent follow-up examinations.
9. Provide support and encouragement to help the patient and his family cope with this long-term illness.
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