The aerobic actinomycetes have been described as consisting of "heterogeneous and taxonomically divergent genera."35 As mentioned previously, many taxonomy changes have taken place with the advent of genetic testing.
Similar, less commonly isolated organisms within the aerobic actinomycetes are listed in Table 8.36
Table 8. Characteristics of Similar Organisms.
| Other Similar Organisms | Notable Characteristics |
Amycolata, Amycolatopsis, Pseudonocardia
| Amycolata and Amycolatopsis were removed from the Nocardia genus because they are modified acid-fast negative
Rarely associated with human disease; an isolate found in the infected pharyngeal mucosa of an elderly patient |
Dermatophilus (D. congolensis)
| Causing disease in cattle; in humans, skin lesions and chronic nodular disease |
Dietzia (D. maris, D. cinnamea, D. pappillomatosis, D. aurantiaca)
| Once considered a Rhodococcus
D. maris is most often identified; causes bacteremia; associated with an infection of a hip prosthesis |
Nocardiopsis (N. dassonvillei and N. synnemataformans)
| Members of Actinomadura dassovillei were moved recently to Nocardiopsis.
Causes mycetoma and abscesses |
| Segniliparus (S. rotundus and S. rugosus) | Strongly acid-fast
Most closely related to Rhodococcus
S rotundus isolated from bronchial isolates, S. rugosus associated with cystic fibrosis patients |
35. Mochon, A. B., Sussland, D., & Saubolle, M. A. (2016). Aerobic Actinomycetes of Clinical Significance. Microbiology spectrum, 4(4), 10.1128/microbiolspec.DMIH2-0021-2015. https://doi.org/10.1128/microbiolspec.DMIH2-0021-201536. Carroll, K.C. & Pfaller, M.A. (Eds.). (2023). Manual of Clinical Microbiology (13th ed.). ASM Press.
Figure 24. CDC/Berd. (1972). Image #3078. This photograph depicted three slant cultures, which demonstrated the variations in colonial appearance among aerobic Actinomycetales bacteria. PHIL public domain. https://phil.cdc.gov/Details.aspx?pid=3078
