253 - Nocardia Species

Abstract

Nocardiosis, caused by species of the environmental saprophyte Nocardia, presents with central nervous system (CNS) and/or pulmonary disease or disseminated disease in the presence of immunocompromise, some chronic lung diseases or alcoholism, and with primary skin disease in the immunocompetent host. Molecular genotyping has determined that the genus Nocardia contains more than 100 species, but relatively few cause human disease. Of these the most common causes of lung disease are Nocardia cyriacigeorgica, Nocardia nova, Nocardia farcinica, and of skin diseases, especially mycetoma, Nocardia brasiliensis. Nocardia farcinica has been linked with CNS nocardiosis and N. nova with bacteremia. Speciation and antimicrobial susceptibility testing are increasingly important components of microbiologic diagnosis, with accurate speciation dependent on access to nucleic acid–based assays or proteomic methods, such as matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy. Imaging forms part of the diagnostic workup, with cerebral imaging, preferably magnetic resonance imaging, recommended in all cases of pulmonary and disseminated nocardiosis. Trimethoprim-sulfamethoxazole is the mainstay of treatment, and monotherapy is usually successful in patients with skin infection or localized mycetoma. Combination therapy is indicated in immunocompromised hosts and all patients with CNS nocardiosis, disseminated disease, or extensive mycetomas.