RT Book, Section A1 Filice, Gregory A. A2 Kasper, Dennis L. A2 Fauci, Anthony S. SR Print(0) ID 1141409194 T1 NOCARDIOSIS T2 Harrison's Infectious Diseases, 3e YR 2017 FD 2017 PB McGraw-Hill Education PP New York, NY SN 9781259835971 LK accessbiomedicalscience.mhmedical.com/content.aspx?aid=1141409194 RD 2024/10/04 AB Nocardia, a genus of saprophytic aerobic actinomycetes that are common worldwide, resides in soil, contributing to the decay of organic matter. Nearly 100 species have been identified, mostly on the basis of 16S rRNA gene sequences. Nocardiae are relatively inactive in standard biochemical tests, and speciation is difficult without molecular phylogenetic techniques. Historically, the majority of isolates associated with pneumonia and systemic disease were identified as Nocardia asteroides, but the lineage of the type strain was muddled, and it is now clear that human disease is associated with several species. Most clinical laboratories cannot speciate isolates accurately and may identify them simply as N. asteroides or Nocardia species.