Nocardia are aerobic,Gram-positive bacilli that form branched hyphae, which are easily disrupted into rods and cocci. Although they often resemble fungi in their microscopic morphology, they grow well on standard nonselective media and are true bacteria. The laboratory diagnosis may be difficult, because the Gram reaction may be weak or irregular. This causes an appearance of "beading," which is similar to Gram-positive cocci. If the isolate is also acid-fast, the possibility of it being Nocardia is high. If Nocardia is isolated, it should not be ignored, as it is rarely a laboratory contaminant.
Disseminated nocardiosis is rare, and most commonly affects immunocompromised patients. Patients receiving radiotherapy, immunosuppressive drugs, or corticosteroids are particularly susceptible to this infection.[2,3] Disseminated nocardiosis has an annual incidence of 500–1,000 cases in the United States.[1,3] It usually begins as a pulmonary infection, because transmission most commonly occurs via inhalation. The Nocardia organisms then disseminate hematogenously. A primary cutaneous infection can also result from direct inoculation of the micro-organism. The primary route of infection in our patient is unknown. It is suspected that she most likely inhaled the organism while cleaning her moldy basement. However, it is also possible that the infection was seeded due to trauma to her lower extremity.
Nocardia nova is one of sixteen Nocardia species that have been implicated in human infection. It is often insidious in onset, and is difficult to diagnose and treat successfully.[8,2] It can invade the brain silently and persist as an inapparent infection. Diagnosis is often delayed because of its commonly nonspecific radiological presentation. Furthermore, bacterial cultures are often discarded before visualization of the Nocardia species, because they are fastidious organisms.[2,9,10]Nocardia nova is usually susceptible to amoxicillin, erythromycin, or a combination of trimethoprim and sulfamethoxazole. Most patients can be treated with outpatient oral therapy. The duration of therapy depends on the severity of infection. For mild infection, defined as cutaneous lesions only, treatment time is three months. The duration of therapy increases to six months for pulmonary lesions, and up to twelve months for severe infection involving the central nervous system.[6,7] Our patient had disseminated nocardiosis nova that was susceptible to trimethoprim and sulfamethoxazole. Because she had disseminated nocardiosis with CNS involvement, she was treated with double-strength trimethoprim and sulfamethoxazole, six tablets three times a day, which was gradually tapered over a period of twelve months.
South Med J. 2010;103(12):1269-1271. © 2010 Lippincott Williams & Wilkins
Cite this: Disseminated Nocardia Nova Infection - Medscape - Dec 01, 2010.