Nocardiosis is typically regarded as an opportunistic infection, but approximately one-third of infected patients are immunocompetent.
Nocardiosis is an infection caused by bacteria (Nocardia) which live in the soil. It occurs primarily in individuals with weakened immune systems. Nocardiosis is found throughout the world among people of all ages, although it is most common in older people and males. Nocardia infection is a chronic bacterial infection that usually originates in the lungs and tends to spread to other organ systems most commonly the brain and the skin. It may also involve the kidneys, the joints, the heart, the eyes, and the bones. While individuals with normal immune systems can acquire this infection.
The major risk factors for nocardiosis are a weakened immune system or chronic lung disease. Nocardiosis is rare in AIDS patients. It is not transmitted by person-to-person contact. Nocardiosis occurs in males more frequently than in females, in a ratio of 3:1. This is thought to be related to an exposure frequency difference rather than a sex difference in susceptibility to infection. Nocardiosis usually begins as a subacute pulmonary infection that resembles actinomycosis.
In about one-third of patients, the infection spreads from the blood into the brain, causing brain abscesses. Nocardia is more likely to disseminate locally or hematogenously. The most common symptoms of pulmonary involvement cough, fever, chills, chest ache, weakness, anorexia, and weight loss. Skin or subcutaneous abscesses occur frequently, sometimes as a primary local inoculation. They may appear as firm cellulites, a lymphocutaneous syndrome, or an actinomycetoma. The lymphocutaneous syndrome consists of a primary pyoderma lesion and lymphatic nodules resembling sporotrichosis.
An actinomycetoma starts as a nodule, suppurates, spreads along fascial planes, and drains through chronic fistulas. Treatment of nocardiosis involves bed rest and high doses of medications. Sulfamethoxazole-trimethoprim (Bactrim) is used most frequently. Additional concurrent therapy with an aminoglycoside plus ceftriaxone benefits patients with fulminant disease. With proper antibiotic treatment, full recovery from nocardiosis is likely. Skin lesions may need to be surgically drained or removed. Surgical therapy to drain abscesses is usually helpful; however, brain abscesses may respond to antimicrobial treatment without surgery.
