İ. Çağatay Acuner M.D., Clinical Microbiologist , Associate Professor Department of Microbiology Faculty of Medicine , Yeditepe University , Istanbul [email protected] Nocardia (Aerobic Actinomycetes). Nocardia (Actinomycetes). Nocardia (Actinomycetes).
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Acid-fast stain of Nocardia species in expectorated sputum. In contrast with the mycobacteria, members of the genus Nocardia do not uniformly retain the stain ("partially acid-fast").
Gram stain of Nocardia species in expectorated sputum. Note the delicate beaded filaments.
Aerial hyphae of Nocardia.
Orange colonies of Nocardia
Nocardiosis: Clinical syndromes
Bronchopulmonary disease: pulmonary disease with necrosis and abscess formation; dissemination to central nervous system or skin is common
Mycetoma: chronic, destructive, progressive disease, generally of extremities, characterized by suppurative granulomas, progressive fibrosis and necrosis, and sinus tract formation
Lymphocutaneous disease: primary infection or secondary spread to cutaneous site characterized by chronic granuloma formation and erythematous subcutaneous nodules, with eventual ulcer formation
Cellulitis and subcutaneous abscesses: granulomatous ulcer formation with surrounding erythema but minimal or no involvement of the draining lymph nodes
Brain abscess: chronic infection with fever, headache, and focal deficits related to the location of the slowly developing abscess(es)
Cutaneous lesion caused by Nocardia
Treatment, Prevention, and Control
Nocardia infections are treated with the combination of antibiotics and appropriate surgical intervention. Trimethoprim-sulfamethoxazole is used most commonly to treat localized infections.
In patients with severe, progressive disease, a combination of antibiotics is recommended, such as amikacin with a carbapenem (e.g., imipenem, meropenem) or broad-spectrum cephalosporin.
In vitro susceptibility tests can be used to guide the selection of antibiotics. Because nocardiae can disseminate and produce significant disease, therapy should be extended for 6 weeks or more.
Whereas the clinical response is favorable in patients with localized infections, the prognosis is poor for immunocompromised patients with disseminated disease.
Nocardiae are ubiquitous, so it is impossible to avoid exposure to them. However, bronchopulmonary disease caused by nocardiae is uncommon in immunocompetent persons, and primary cutaneous infections can be prevented with proper wound care.