Important note: Routine culture media should be held for at least 14 days. If aerobic actinomycetes are suspected, the provider should notify the microbiology laboratory in addition to placing special bacteriology test orders (as appropriate).
Primary isolation media:
The following routine agar is recommended by the American Society for Microbiology (ASM) when setting up or inoculating specimens onto plates19:
- Primary plates should always include blood agar (and adding chocolate agar is helpful).
- Sterile body site specimens should be inoculated to:
- Blood agar and chocolate agar plates at 35°C
- Lowenstein-Jensen slant at 35°C
- Sabouraud dextrose agar at 35°C
- Thio broth at 35°C
- Tryptic soy broth (TSB) at 35°C
- Nonsterile body site specimens should be inoculated to:
- The initial primary media (as above for sterile body sites), and
- Selective media (listed on the next page)
Note: Overgrowth of nonpathogenic colonizers may mask the growth of the aerobic actinomycetes. Selective media may be used; these are discussed on the next page. In addition, the microbiologist should always be on the lookout for yeast and fungal organism growth.
After initial growth is achieved:
- Subculture to media at different temperatures (25°C, 35°C, 45°C).
- This will help determine the optimal growth temperature of suspected actinomycetes. (Refer to section, "Description of the Genera and Species.")
19. Leber AL, ed. Clinical microbiology procedures handbook. 4th ed. ASM Press; 2016:Section 6.
20. CDC/Berd. Image #18858. These slant cultures demonstrated the similarity in colonial morphology between three aerobic,
Actinomycetes spp. bacteria. From left to right, you can see that the colonial growth of
Nocardia asteroides [now renamed as
N. abscessus, N. nova, and others],
N. caviae, and
N. brasiliensis, are all very similar.
Nocardia spp. colonies can be smooth, but in this case, all these organisms produced colonies that would be described as mold-like, or verrucous, though
N. caviae produced a colony that was smoother than the other two species. All produced colonies that were yellowish-beige in color. PHIL public domain. Created 2014. Accessed October 27, 2022.
https://phil.cdc.gov/Details.aspx?pid=1885821. CDC/Kaplan. Image #18867. This slant culture containing a Löwenstein–Jensen (L-J) agar growth medium, demonstrated the colonial morphology produced by Nocardia asteroides [now renamed as individual Nocardia species] bacteria. Nocardia spp. colonies can be smooth, but in this case, these organisms produced colonies that may be described as mold-like, or verrucous, and exhibited a pinkish coloration. PHIL public domain. Created 1969. Accessed October 27, 2022. https://phil.cdc.gov/Details.aspx?pid=18867
